Changeset 12063 for NEMO/branches/2019/dev_ASINTER-01-05_merged/doc/latex/NEMO/subfiles/chap_SBC.tex
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r11263 r12063 1 1 \documentclass[../main/NEMO_manual]{subfiles} 2 \usepackage{fontspec} 3 \usepackage{fontawesome} 2 4 3 5 \begin{document} 4 % ================================================================ 5 % Chapter —— Surface Boundary Condition (SBC, ISF, ICB) 6 % ================================================================ 7 \chapter{Surface Boundary Condition (SBC, ISF, ICB)} 6 7 \chapter{Surface Boundary Condition (SBC, SAS, ISF, ICB)} 8 8 \label{chap:SBC} 9 \minitoc 10 11 \newpage 12 13 %---------------------------------------namsbc-------------------------------------------------- 14 15 \nlst{namsbc} 16 %-------------------------------------------------------------------------------------------------------------- 17 18 The ocean needs six fields as surface boundary condition: 9 10 \thispagestyle{plain} 11 12 \chaptertoc 13 14 \paragraph{Changes record} ~\\ 15 16 {\footnotesize 17 \begin{tabularx}{\textwidth}{l||X|X} 18 Release & Author(s) & Modifications \\ 19 \hline 20 {\em 4.0} & {\em ...} & {\em ...} \\ 21 {\em 3.6} & {\em ...} & {\em ...} \\ 22 {\em 3.4} & {\em ...} & {\em ...} \\ 23 {\em <=3.4} & {\em ...} & {\em ...} 24 \end{tabularx} 25 } 26 27 \clearpage 28 29 \begin{listing} 30 \nlst{namsbc} 31 \caption{\forcode{&namsbc}} 32 \label{lst:namsbc} 33 \end{listing} 34 35 The ocean needs seven fields as surface boundary condition: 36 19 37 \begin{itemize} 20 \item 21 the two components of the surface ocean stress $\left( {\tau_u \;,\;\tau_v} \right)$ 22 \item 23 the incoming solar and non solar heat fluxes $\left( {Q_{ns} \;,\;Q_{sr} } \right)$ 24 \item 25 the surface freshwater budget $\left( {\textit{emp}} \right)$ 26 \item 27 the surface salt flux associated with freezing/melting of seawater $\left( {\textit{sfx}} \right)$ 38 \item the two components of the surface ocean stress $\left( {\tau_u \;,\;\tau_v} \right)$ 39 \item the incoming solar and non solar heat fluxes $\left( {Q_{ns} \;,\;Q_{sr} } \right)$ 40 \item the surface freshwater budget $\left( {\textit{emp}} \right)$ 41 \item the surface salt flux associated with freezing/melting of seawater $\left( {\textit{sfx}} \right)$ 42 \item the atmospheric pressure at the ocean surface $\left( p_a \right)$ 28 43 \end{itemize} 29 plus an optional field: 44 45 Four different ways are available to provide the seven fields to the ocean. They are controlled by 46 namelist \nam{sbc}{sbc} variables: 47 30 48 \begin{itemize} 31 \item the atmospheric pressure at the ocean surface $\left( p_a \right)$ 49 \item a bulk formulation (\np[=.true.]{ln_blk}{ln\_blk}), featuring a selection of four bulk parameterization algorithms, 50 \item a flux formulation (\np[=.true.]{ln_flx}{ln\_flx}), 51 \item a coupled or mixed forced/coupled formulation (exchanges with a atmospheric model via the OASIS coupler), 52 (\np{ln_cpl}{ln\_cpl} or \np[=.true.]{ln_mixcpl}{ln\_mixcpl}), 53 \item a user defined formulation (\np[=.true.]{ln_usr}{ln\_usr}). 32 54 \end{itemize} 33 55 34 Four different ways to provide the first six fields to the ocean are available which are controlled by 35 namelist \ngn{namsbc} variables: 36 an analytical formulation (\np{ln\_ana}\forcode{ = .true.}), 37 a flux formulation (\np{ln\_flx}\forcode{ = .true.}), 38 a bulk formulae formulation (CORE (\np{ln\_blk\_core}\forcode{ = .true.}), 39 CLIO (\np{ln\_blk\_clio}\forcode{ = .true.}) bulk formulae) and 40 a coupled or mixed forced/coupled formulation (exchanges with a atmospheric model via the OASIS coupler) 41 (\np{ln\_cpl} or \np{ln\_mixcpl}\forcode{ = .true.}). 42 When used (\ie \np{ln\_apr\_dyn}\forcode{ = .true.}), 43 the atmospheric pressure forces both ocean and ice dynamics. 44 45 The frequency at which the forcing fields have to be updated is given by the \np{nn\_fsbc} namelist parameter. 46 When the fields are supplied from data files (flux and bulk formulations), 47 the input fields need not be supplied on the model grid. 48 Instead a file of coordinates and weights can be supplied which maps the data from the supplied grid to 56 The frequency at which the forcing fields have to be updated is given by the \np{nn_fsbc}{nn\_fsbc} namelist parameter. 57 58 When the fields are supplied from data files (bulk, flux and mixed formulations), 59 the input fields do not need to be supplied on the model grid. 60 Instead, a file of coordinates and weights can be supplied to map the data from the input fields grid to 49 61 the model points (so called "Interpolation on the Fly", see \autoref{subsec:SBC_iof}). 50 If the Interpolation on the Fly option is used, input data belonging to land points (in the native grid),51 can be masked to avoid spurious results in proximity of the coastsas62 If the "Interpolation on the Fly" option is used, input data belonging to land points (in the native grid) 63 should be masked or filled to avoid spurious results in proximity of the coasts, as 52 64 large sea-land gradients characterize most of the atmospheric variables. 53 65 54 66 In addition, the resulting fields can be further modified using several namelist options. 55 These options control 67 These options control: 68 56 69 \begin{itemize} 57 \item 58 the rotation of vector components supplied relative to an east-north coordinate system onto 59 the local grid directions in the model; 60 \item 61 the addition of a surface restoring term to observed SST and/or SSS (\np{ln\_ssr}\forcode{ = .true.}); 62 \item 63 the modification of fluxes below ice-covered areas (using observed ice-cover or a sea-ice model) 64 (\np{nn\_ice}\forcode{ = 0..3}); 65 \item 66 the addition of river runoffs as surface freshwater fluxes or lateral inflow (\np{ln\_rnf}\forcode{ = .true.}); 67 \item 68 the addition of isf melting as lateral inflow (parameterisation) or 69 as fluxes applied at the land-ice ocean interface (\np{ln\_isf}) ; 70 \item 71 the addition of a freshwater flux adjustment in order to avoid a mean sea-level drift 72 (\np{nn\_fwb}\forcode{ = 0..2}); 73 \item 74 the transformation of the solar radiation (if provided as daily mean) into a diurnal cycle 75 (\np{ln\_dm2dc}\forcode{ = .true.}); 76 \item 77 a neutral drag coefficient can be read from an external wave model (\np{ln\_cdgw}\forcode{ = .true.}); 78 \item 79 the Stokes drift rom an external wave model can be accounted (\np{ln\_sdw}\forcode{ = .true.}); 80 \item 81 the Stokes-Coriolis term can be included (\np{ln\_stcor}\forcode{ = .true.}); 82 \item 83 the surface stress felt by the ocean can be modified by surface waves (\np{ln\_tauwoc}\forcode{ = .true.}). 70 \item the rotation of vector components supplied relative to an east-north coordinate system onto 71 the local grid directions in the model, 72 \item the use of a land/sea mask for input fields (\np[=.true.]{nn_lsm}{nn\_lsm}), 73 \item the addition of a surface restoring term to observed SST and/or SSS (\np[=.true.]{ln_ssr}{ln\_ssr}), 74 \item the modification of fluxes below ice-covered areas (using climatological ice-cover or a sea-ice model) 75 (\np[=0..3]{nn_ice}{nn\_ice}), 76 \item the addition of river runoffs as surface freshwater fluxes or lateral inflow (\np[=.true.]{ln_rnf}{ln\_rnf}), 77 \item the addition of ice-shelf melting as lateral inflow (parameterisation) or 78 as fluxes applied at the land-ice ocean interface (\np[=.true.]{ln_isf}{ln\_isf}), 79 \item the addition of a freshwater flux adjustment in order to avoid a mean sea-level drift 80 (\np[=0..2]{nn_fwb}{nn\_fwb}), 81 \item the transformation of the solar radiation (if provided as daily mean) into an analytical diurnal cycle 82 (\np[=.true.]{ln_dm2dc}{ln\_dm2dc}), 83 \item the activation of wave effects from an external wave model (\np[=.true.]{ln_wave}{ln\_wave}), 84 \item a neutral drag coefficient is read from an external wave model (\np[=.true.]{ln_cdgw}{ln\_cdgw}), 85 \item the Stokes drift from an external wave model is accounted for (\np[=.true.]{ln_sdw}{ln\_sdw}), 86 \item the choice of the Stokes drift profile parameterization (\np[=0..2]{nn_sdrift}{nn\_sdrift}), 87 \item the surface stress given to the ocean is modified by surface waves (\np[=.true.]{ln_tauwoc}{ln\_tauwoc}), 88 \item the surface stress given to the ocean is read from an external wave model (\np[=.true.]{ln_tauw}{ln\_tauw}), 89 \item the Stokes-Coriolis term is included (\np[=.true.]{ln_stcor}{ln\_stcor}), 90 \item the light penetration in the ocean (\np[=.true.]{ln_traqsr}{ln\_traqsr} with namelist \nam{tra_qsr}{tra\_qsr}), 91 \item the atmospheric surface pressure gradient effect on ocean and ice dynamics (\np[=.true.]{ln_apr_dyn}{ln\_apr\_dyn} with namelist \nam{sbc_apr}{sbc\_apr}), 92 \item the effect of sea-ice pressure on the ocean (\np[=.true.]{ln_ice_embd}{ln\_ice\_embd}). 84 93 \end{itemize} 85 94 86 In this chapter, we first discuss where the surface boundary condition appearsin the model equations.87 Then we present the five ways of providing the surface boundary condition,88 followed by the description of the atmospheric pressure and the river runoff. 89 Next the scheme for interpolation on the fly is described.95 In this chapter, we first discuss where the surface boundary conditions appear in the model equations. 96 Then we present the three ways of providing the surface boundary conditions, 97 followed by the description of the atmospheric pressure and the river runoff. 98 Next, the scheme for interpolation on the fly is described. 90 99 Finally, the different options that further modify the fluxes applied to the ocean are discussed. 91 One of these is modification by icebergs (see \autoref{sec: ICB_icebergs}),100 One of these is modification by icebergs (see \autoref{sec:SBC_ICB_icebergs}), 92 101 which act as drifting sources of fresh water. 93 Another example of modification is that due to the ice shelf melting/freezing (see \autoref{sec:SBC_isf}), 102 Another example of modification is that due to the ice shelf melting/freezing (see \autoref{sec:SBC_isf}), 94 103 which provides additional sources of fresh water. 95 104 96 97 % ================================================================ 98 % Surface boundary condition for the ocean 99 % ================================================================ 105 %% ================================================================================================= 100 106 \section{Surface boundary condition for the ocean} 101 \label{sec:SBC_ general}107 \label{sec:SBC_ocean} 102 108 103 109 The surface ocean stress is the stress exerted by the wind and the sea-ice on the ocean. 104 110 It is applied in \mdl{dynzdf} module as a surface boundary condition of the computation of 105 the momentum vertical mixing trend (see \autoref{eq: dynzdf_sbc} in \autoref{sec:DYN_zdf}).111 the momentum vertical mixing trend (see \autoref{eq:DYN_zdf_sbc} in \autoref{sec:DYN_zdf}). 106 112 As such, it has to be provided as a 2D vector interpolated onto the horizontal velocity ocean mesh, 107 \ie resolved onto the model (\textbf{i},\textbf{j}) direction at $u$- and $v$-points.113 \ie\ resolved onto the model (\textbf{i},\textbf{j}) direction at $u$- and $v$-points. 108 114 109 115 The surface heat flux is decomposed into two parts, a non solar and a solar heat flux, 110 116 $Q_{ns}$ and $Q_{sr}$, respectively. 111 117 The former is the non penetrative part of the heat flux 112 (\ie the sum of sensible, latent and long wave heat fluxes plus113 the heat content of the mass exchange with the atmosphereand sea-ice).118 (\ie\ the sum of sensible, latent and long wave heat fluxes plus 119 the heat content of the mass exchange between the ocean and sea-ice). 114 120 It is applied in \mdl{trasbc} module as a surface boundary condition trend of 115 121 the first level temperature time evolution equation 116 (see \autoref{eq: tra_sbc} and \autoref{eq:tra_sbc_lin} in \autoref{subsec:TRA_sbc}).122 (see \autoref{eq:TRA_sbc} and \autoref{eq:TRA_sbc_lin} in \autoref{subsec:TRA_sbc}). 117 123 The latter is the penetrative part of the heat flux. 118 It is applied as a 3D trend sof the temperature equation (\mdl{traqsr} module) when119 \np {ln\_traqsr}\forcode{ = .true.}.124 It is applied as a 3D trend of the temperature equation (\mdl{traqsr} module) when 125 \np[=.true.]{ln_traqsr}{ln\_traqsr}. 120 126 The way the light penetrates inside the water column is generally a sum of decreasing exponentials 121 (see \autoref{subsec:TRA_qsr}). 127 (see \autoref{subsec:TRA_qsr}). 122 128 123 129 The surface freshwater budget is provided by the \textit{emp} field. 124 130 It represents the mass flux exchanged with the atmosphere (evaporation minus precipitation) and 125 131 possibly with the sea-ice and ice shelves (freezing minus melting of ice). 126 It affects boththe ocean in two different ways:127 $(i)$ it changes the volume of the ocean and therefore appears in the sea surface height equation as128 a volume flux, and 132 It affects the ocean in two different ways: 133 $(i)$ it changes the volume of the ocean, and therefore appears in the sea surface height equation as %GS: autoref ssh equation to be added 134 a volume flux, and 129 135 $(ii)$ it changes the surface temperature and salinity through the heat and salt contents of 130 the mass exchanged with the atmosphere, the sea-ice and the ice shelves. 131 136 the mass exchanged with atmosphere, sea-ice and ice shelves. 132 137 133 138 %\colorbox{yellow}{Miss: } 134 % 135 %A extensive description of all namsbc namelist (parameter that have to be 139 %A extensive description of all namsbc namelist (parameter that have to be 136 140 %created!) 137 % 138 %Especially the \np{nn\_fsbc}, the \mdl{sbc\_oce} module (fluxes + mean sst sss ssu 139 %ssv) \ie information required by flux computation or sea-ice 140 % 141 %\mdl{sbc\_oce} containt the definition in memory of the 7 fields (6+runoff), add 141 %Especially the \np{nn_fsbc}{nn\_fsbc}, the \mdl{sbc\_oce} module (fluxes + mean sst sss ssu 142 %ssv) \ie\ information required by flux computation or sea-ice 143 %\mdl{sbc\_oce} containt the definition in memory of the 7 fields (6+runoff), add 142 144 %a word on runoff: included in surface bc or add as lateral obc{\ldots}. 143 %144 145 %Sbcmod manage the ``providing'' (fourniture) to the ocean the 7 fields 145 % 146 %Fluxes update only each nf{\_}sbc time step (namsbc) explain relation 147 %between nf{\_}sbc and nf{\_}ice, do we define nf{\_}blk??? ? only one 148 %nf{\_}sbc 149 % 146 %Fluxes update only each nf\_sbc time step (namsbc) explain relation 147 %between nf\_sbc and nf\_ice, do we define nf\_blk??? ? only one 148 %nf\_sbc 150 149 %Explain here all the namlist namsbc variable{\ldots}. 151 %152 150 % explain : use or not of surface currents 153 %154 151 %\colorbox{yellow}{End Miss } 155 152 156 153 The ocean model provides, at each time step, to the surface module (\mdl{sbcmod}) 157 the surface currents, temperature and salinity. 158 These variables are averaged over \np{nn\_fsbc} time-step (\autoref{tab:ssm}), and 159 it is these averaged fields which are used to computes the surface fluxes at a frequency of \np{nn\_fsbc} time-step. 160 161 162 %-------------------------------------------------TABLE--------------------------------------------------- 154 the surface currents, temperature and salinity. 155 These variables are averaged over \np{nn_fsbc}{nn\_fsbc} time-step (\autoref{tab:SBC_ssm}), and 156 these averaged fields are used to compute the surface fluxes at the frequency of \np{nn_fsbc}{nn\_fsbc} time-steps. 157 163 158 \begin{table}[tb] 164 \begin{center} 165 \begin{tabular}{|l|l|l|l|} 166 \hline 167 Variable description & Model variable & Units & point \\ \hline 168 i-component of the surface current & ssu\_m & $m.s^{-1}$ & U \\ \hline 169 j-component of the surface current & ssv\_m & $m.s^{-1}$ & V \\ \hline 170 Sea surface temperature & sst\_m & \r{}$K$ & T \\ \hline 171 Sea surface salinty & sss\_m & $psu$ & T \\ \hline 172 \end{tabular} 173 \caption{ 174 \protect\label{tab:ssm} 175 Ocean variables provided by the ocean to the surface module (SBC). 176 The variable are averaged over nn{\_}fsbc time step, 177 \ie the frequency of computation of surface fluxes. 178 } 179 \end{center} 159 \centering 160 \begin{tabular}{|l|l|l|l|} 161 \hline 162 Variable description & Model variable & Units & point \\ 163 \hline 164 i-component of the surface current & ssu\_m & $m.s^{-1}$ & U \\ 165 \hline 166 j-component of the surface current & ssv\_m & $m.s^{-1}$ & V \\ 167 \hline 168 Sea surface temperature & sst\_m & \r{}$K$ & T \\\hline 169 Sea surface salinty & sss\_m & $psu$ & T \\ \hline 170 \end{tabular} 171 \caption[Ocean variables provided to the surface module)]{ 172 Ocean variables provided to the surface module (\texttt{SBC}). 173 The variable are averaged over \protect\np{nn_fsbc}{nn\_fsbc} time-step, 174 \ie\ the frequency of computation of surface fluxes.} 175 \label{tab:SBC_ssm} 180 176 \end{table} 181 %-------------------------------------------------------------------------------------------------------------- 182 183 %\colorbox{yellow}{Penser a} mettre dans le restant l'info nn{\_}fsbc ET nn{\_}fsbc*rdt de sorte de reinitialiser la moyenne si on change la frequence ou le pdt 184 185 186 % ================================================================ 187 % Input Data 188 % ================================================================ 177 178 %\colorbox{yellow}{Penser a} mettre dans le restant l'info nn\_fsbc ET nn\_fsbc*rdt de sorte de reinitialiser la moyenne si on change la frequence ou le pdt 179 180 %% ================================================================================================= 189 181 \section{Input data generic interface} 190 182 \label{sec:SBC_input} 191 183 192 184 A generic interface has been introduced to manage the way input data 193 (2D or 3D fields, like surface forcing or ocean T and S) are specif yin \NEMO.194 This task is a rchieved by \mdl{fldread}.195 The module was design with four main objectives in mind:185 (2D or 3D fields, like surface forcing or ocean T and S) are specified in \NEMO. 186 This task is achieved by \mdl{fldread}. 187 The module is designed with four main objectives in mind: 196 188 \begin{enumerate} 197 \item 198 optionally provide a time interpolation of the input data at model time-step, whatever their input frequency is, 189 \item optionally provide a time interpolation of the input data every specified model time-step, whatever their input frequency is, 199 190 and according to the different calendars available in the model. 200 \item 201 optionally provide an on-the-fly space interpolation from the native input data grid to the model grid. 202 \item 203 make the run duration independent from the period cover by the input files. 204 \item 205 provide a simple user interface and a rather simple developer interface by 206 limiting the number of prerequisite information. 207 \end{enumerate} 208 209 As a results the user have only to fill in for each variable a structure in the namelist file to 191 \item optionally provide an on-the-fly space interpolation from the native input data grid to the model grid. 192 \item make the run duration independent from the period cover by the input files. 193 \item provide a simple user interface and a rather simple developer interface by 194 limiting the number of prerequisite informations. 195 \end{enumerate} 196 197 As a result, the user has only to fill in for each variable a structure in the namelist file to 210 198 define the input data file and variable names, the frequency of the data (in hours or months), 211 199 whether its is climatological data or not, the period covered by the input file (one year, month, week or day), 212 and three additional parameters for on-the-fly interpolation.200 and three additional parameters for the on-the-fly interpolation. 213 201 When adding a new input variable, the developer has to add the associated structure in the namelist, 214 202 read this information by mirroring the namelist read in \rou{sbc\_blk\_init} for example, 215 203 and simply call \rou{fld\_read} to obtain the desired input field at the model time-step and grid points. 216 204 217 The only constraints are that the input file is a NetCDF file, the file name follows a nomenclature 205 The only constraints are that the input file is a NetCDF file, the file name follows a nomenclature 218 206 (see \autoref{subsec:SBC_fldread}), the period it cover is one year, month, week or day, and, 219 207 if on-the-fly interpolation is used, a file of weights must be supplied (see \autoref{subsec:SBC_iof}). 220 208 221 209 Note that when an input data is archived on a disc which is accessible directly from the workspace where 222 the code is executed, then the use can set the \np{cn\_dir} to the pathway leading to the data. 223 By default, the data are assumed to have been copied so that cn\_dir='./'. 224 225 % ------------------------------------------------------------------------------------------------------------- 226 % Input Data specification (\mdl{fldread}) 227 % ------------------------------------------------------------------------------------------------------------- 228 \subsection[Input data specification (\textit{fldread.F90})] 229 {Input data specification (\protect\mdl{fldread})} 210 the code is executed, then the user can set the \np{cn_dir}{cn\_dir} to the pathway leading to the data. 211 By default, the data are assumed to be in the same directory as the executable, so that cn\_dir='./'. 212 213 %% ================================================================================================= 214 \subsection[Input data specification (\textit{fldread.F90})]{Input data specification (\protect\mdl{fldread})} 230 215 \label{subsec:SBC_fldread} 231 216 232 217 The structure associated with an input variable contains the following information: 233 218 \begin{forlines} 234 ! file name ! frequency (hours) ! variable ! time interp. ! clim ! 'yearly'/ ! weights ! rotation ! land/sea mask ! 219 ! file name ! frequency (hours) ! variable ! time interp. ! clim ! 'yearly'/ ! weights ! rotation ! land/sea mask ! 235 220 ! ! (if <0 months) ! name ! (logical) ! (T/F) ! 'monthly' ! filename ! pairing ! filename ! 236 221 \end{forlines} 237 where 238 \begin{description} 239 \item[File name]: 240 the stem name of the NetCDF file to be open. 222 where 223 \begin{description} 224 \item [File name]: the stem name of the NetCDF file to be opened. 241 225 This stem will be completed automatically by the model, with the addition of a '.nc' at its end and 242 226 by date information and possibly a prefix (when using AGRIF). 243 Tab.\autoref{tab:fldread} provides the resulting file name in all possible cases according to227 \autoref{tab:SBC_fldread} provides the resulting file name in all possible cases according to 244 228 whether it is a climatological file or not, and to the open/close frequency (see below for definition). 245 246 %--------------------------------------------------TABLE--------------------------------------------------247 229 \begin{table}[htbp] 248 \begin{center} 249 \begin{tabular}{|l|c|c|c|} 250 \hline 251 & daily or weekLLL & monthly & yearly \\ \hline 252 \np{clim}\forcode{ = .false.} & fn\_yYYYYmMMdDD.nc & fn\_yYYYYmMM.nc & fn\_yYYYY.nc \\ \hline 253 \np{clim}\forcode{ = .true.} & not possible & fn\_m??.nc & fn \\ \hline 254 \end{tabular} 255 \end{center} 256 \caption{ 257 \protect\label{tab:fldread} 258 naming nomenclature for climatological or interannual input file, as a function of the Open/close frequency. 230 \centering 231 \begin{tabular}{|l|c|c|c|} 232 \hline 233 & daily or weekLL & monthly & yearly \\ 234 \hline 235 \np[=.false.]{clim}{clim} & fn\_yYYYYmMMdDD.nc & fn\_yYYYYmMM.nc & fn\_yYYYY.nc \\ 236 \hline 237 \np[=.true.]{clim}{clim} & not possible & fn\_m??.nc & fn \\ 238 \hline 239 \end{tabular} 240 \caption[Naming nomenclature for climatological or interannual input file]{ 241 Naming nomenclature for climatological or interannual input file, 242 as a function of the open/close frequency. 259 243 The stem name is assumed to be 'fn'. 260 244 For weekly files, the 'LLL' corresponds to the first three letters of the first day of the week 261 (\ie 'sun','sat','fri','thu','wed','tue','mon'). 262 The 'YYYY', 'MM' and 'DD' should be replaced by the actual year/month/day, always coded with 4 or 2 digits. 263 Note that (1) in mpp, if the file is split over each subdomain, the suffix '.nc' is replaced by '\_PPPP.nc', 245 (\ie\ 'sun','sat','fri','thu','wed','tue','mon'). 246 The 'YYYY', 'MM' and 'DD' should be replaced by the actual year/month/day, 247 always coded with 4 or 2 digits. 248 Note that (1) in mpp, if the file is split over each subdomain, 249 the suffix '.nc' is replaced by '\_PPPP.nc', 264 250 where 'PPPP' is the process number coded with 4 digits; 265 (2) when using AGRIF, the prefix '\_N' is added to files, where 'N' 251 (2) when using AGRIF, the prefix '\_N' is added to files, where 'N' is the child grid number. 266 252 } 253 \label{tab:SBC_fldread} 267 254 \end{table} 268 %-------------------------------------------------------------------------------------------------------------- 269 270 271 \item[Record frequency]: 272 the frequency of the records contained in the input file. 255 \item [Record frequency]: the frequency of the records contained in the input file. 273 256 Its unit is in hours if it is positive (for example 24 for daily forcing) or in months if negative 274 257 (for example -1 for monthly forcing or -12 for annual forcing). 275 Note that this frequency must really be an integer and not a real. 276 On some computers, seting it to '24.' can be interpreted as 240! 277 278 \item[Variable name]: 279 the name of the variable to be read in the input NetCDF file. 280 281 \item[Time interpolation]: 282 a logical to activate, or not, the time interpolation. 258 Note that this frequency must REALLY be an integer and not a real. 259 On some computers, setting it to '24.' can be interpreted as 240! 260 \item [Variable name]: the name of the variable to be read in the input NetCDF file. 261 \item [Time interpolation]: a logical to activate, or not, the time interpolation. 283 262 If set to 'false', the forcing will have a steplike shape remaining constant during each forcing period. 284 263 For example, when using a daily forcing without time interpolation, the forcing remaining constant from 285 264 00h00'00'' to 23h59'59". 286 265 If set to 'true', the forcing will have a broken line shape. 287 Records are assumed to be dated the middle of the forcing period.266 Records are assumed to be dated at the middle of the forcing period. 288 267 For example, when using a daily forcing with time interpolation, 289 linear interpolation will be performed between mid-day of two consecutive days. 290 291 \item[Climatological forcing]: 292 a logical to specify if a input file contains climatological forcing which can be cycle in time, 268 linear interpolation will be performed between mid-day of two consecutive days. 269 \item [Climatological forcing]: a logical to specify if a input file contains climatological forcing which can be cycle in time, 293 270 or an interannual forcing which will requires additional files if 294 the period covered by the simulation exceed the one of the file. 295 See the above the file naming strategy which impacts the expected name of the file to be opened. 296 297 \item[Open/close frequency]: 298 the frequency at which forcing files must be opened/closed. 271 the period covered by the simulation exceeds the one of the file. 272 See the above file naming strategy which impacts the expected name of the file to be opened. 273 \item [Open/close frequency]: the frequency at which forcing files must be opened/closed. 299 274 Four cases are coded: 300 275 'daily', 'weekLLL' (with 'LLL' the first 3 letters of the first day of the week), 'monthly' and 'yearly' which … … 302 277 Files are assumed to contain data from the beginning of the open/close period. 303 278 For example, the first record of a yearly file containing daily data is Jan 1st even if 304 the experiment is not starting at the beginning of the year. 305 306 \item[Others]: 307 'weights filename', 'pairing rotation' and 'land/sea mask' are associated with 279 the experiment is not starting at the beginning of the year. 280 \item [Others]: 'weights filename', 'pairing rotation' and 'land/sea mask' are associated with 308 281 on-the-fly interpolation which is described in \autoref{subsec:SBC_iof}. 309 310 282 \end{description} 311 283 … … 315 287 the date of the records read in the input files. 316 288 Following \citet{leclair.madec_OM09}, the date of a time step is set at the middle of the time step. 317 For example, for an experiment starting at 0h00'00" with a one 289 For example, for an experiment starting at 0h00'00" with a one-hour time-step, 318 290 a time interpolation will be performed at the following time: 0h30'00", 1h30'00", 2h30'00", etc. 319 291 However, for forcing data related to the surface module, 320 values are not needed at every time-step but at every \np{nn \_fsbc} time-step.321 For example with \np {nn\_fsbc}\forcode{ = 3}, the surface module will be called at time-steps 1, 4, 7, etc.322 The date used for the time interpolation is thus redefined to be at the middle of \np{nn\_fsbc} time-step period.323 In the previous example, this leads to: 1h30'00", 4h30'00", 7h30'00", etc. \\ 292 values are not needed at every time-step but at every \np{nn_fsbc}{nn\_fsbc} time-step. 293 For example with \np[=3]{nn_fsbc}{nn\_fsbc}, the surface module will be called at time-steps 1, 4, 7, etc. 294 The date used for the time interpolation is thus redefined to the middle of \np{nn_fsbc}{nn\_fsbc} time-step period. 295 In the previous example, this leads to: 1h30'00", 4h30'00", 7h30'00", etc. \\ 324 296 (2) For code readablility and maintenance issues, we don't take into account the NetCDF input file calendar. 325 297 The calendar associated with the forcing field is build according to the information provided by 326 298 user in the record frequency, the open/close frequency and the type of temporal interpolation. 327 299 For example, the first record of a yearly file containing daily data that will be interpolated in time is assumed to 328 bestart Jan 1st at 12h00'00" and end Dec 31st at 12h00'00". \\300 start Jan 1st at 12h00'00" and end Dec 31st at 12h00'00". \\ 329 301 (3) If a time interpolation is requested, the code will pick up the needed data in the previous (next) file when 330 302 interpolating data with the first (last) record of the open/close period. 331 For example, if the input file specifications are ''yearly, containing daily data to be interpolated in time'', 303 For example, if the input file specifications are ''yearly, containing daily data to be interpolated in time'', 332 304 the values given by the code between 00h00'00" and 11h59'59" on Jan 1st will be interpolated values between 333 305 Dec 31st 12h00'00" and Jan 1st 12h00'00". 334 306 If the forcing is climatological, Dec and Jan will be keep-up from the same year. 335 307 However, if the forcing is not climatological, at the end of 336 the open/close period the code will automatically close the current file and open the next one.308 the open/close period, the code will automatically close the current file and open the next one. 337 309 Note that, if the experiment is starting (ending) at the beginning (end) of 338 an open/close period we do accept that the previous (next) file is not existing.310 an open/close period, we do accept that the previous (next) file is not existing. 339 311 In this case, the time interpolation will be performed between two identical values. 340 312 For example, when starting an experiment on Jan 1st of year Y with yearly files and daily data to be interpolated, 341 313 we do accept that the file related to year Y-1 is not existing. 342 314 The value of Jan 1st will be used as the missing one for Dec 31st of year Y-1. 343 If the file of year Y-1 exists, the code will read its last record. 315 If the file of year Y-1 exists, the code will read its last record. 344 316 Therefore, this file can contain only one record corresponding to Dec 31st, 345 317 a useful feature for user considering that it is too heavy to manipulate the complete file for year Y-1. 346 318 347 348 % ------------------------------------------------------------------------------------------------------------- 349 % Interpolation on the Fly 350 % ------------------------------------------------------------------------------------------------------------- 319 %% ================================================================================================= 351 320 \subsection{Interpolation on-the-fly} 352 321 \label{subsec:SBC_iof} … … 354 323 Interpolation on the Fly allows the user to supply input files required for the surface forcing on 355 324 grids other than the model grid. 356 To do this he or she must supply, in addition to the source data file, a file of weights to be used to325 To do this, he or she must supply, in addition to the source data file(s), a file of weights to be used to 357 326 interpolate from the data grid to the model grid. 358 327 The original development of this code used the SCRIP package 359 328 (freely available \href{http://climate.lanl.gov/Software/SCRIP}{here} under a copyright agreement). 360 In principle, any package can be used to generate the weights, but the variables in329 In principle, any package such as CDO can be used to generate the weights, but the variables in 361 330 the input weights file must have the same names and meanings as assumed by the model. 362 Two methods are currently available: bilinear and bicubic interpolation .331 Two methods are currently available: bilinear and bicubic interpolations. 363 332 Prior to the interpolation, providing a land/sea mask file, the user can decide to remove land points from 364 333 the input file and substitute the corresponding values with the average of the 8 neighbouring points in … … 366 335 Only "sea points" are considered for the averaging. 367 336 The land/sea mask file must be provided in the structure associated with the input variable. 368 The netcdf land/sea mask variable name must be 'LSM' it must have the same horizontal and vertical dimensions of 369 the associated variable and should be equal to 1 over land and 0 elsewhere. 370 The procedure can be recursively applied setting nn\_lsm > 1 in namsbc namelist. 371 Note that nn\_lsm=0 forces the code to not apply the procedure even if a file for land/sea mask is supplied. 372 337 The netcdf land/sea mask variable name must be 'LSM' and must have the same horizontal and vertical dimensions as 338 the associated variables and should be equal to 1 over land and 0 elsewhere. 339 The procedure can be recursively applied by setting nn\_lsm > 1 in namsbc namelist. 340 Note that nn\_lsm=0 forces the code to not apply the procedure, even if a land/sea mask file is supplied. 341 342 %% ================================================================================================= 373 343 \subsubsection{Bilinear interpolation} 374 344 \label{subsec:SBC_iof_bilinear} … … 376 346 The input weights file in this case has two sets of variables: 377 347 src01, src02, src03, src04 and wgt01, wgt02, wgt03, wgt04. 378 The "src" variables correspond to the point in the input grid to which the weight "wgt" is to beapplied.348 The "src" variables correspond to the point in the input grid to which the weight "wgt" is applied. 379 349 Each src value is an integer corresponding to the index of a point in the input grid when 380 350 written as a one dimensional array. … … 392 362 and wgt(1) corresponds to variable "wgt01" for example. 393 363 364 %% ================================================================================================= 394 365 \subsubsection{Bicubic interpolation} 395 366 \label{subsec:SBC_iof_bicubic} 396 367 397 Again there are two sets of variables: "src" and "wgt".398 But in this case there are 16 of each.368 Again, there are two sets of variables: "src" and "wgt". 369 But in this case, there are 16 of each. 399 370 The symbolic algorithm used to calculate values on the model grid is now: 400 371 … … 402 373 \begin{split} 403 374 f_{m}(i,j) = f_{m}(i,j) +& \sum_{k=1}^{4} {wgt(k)f(idx(src(k)))} 404 + \sum_{k=5}^{8} {wgt(k)\left.\frac{\partial f}{\partial i}\right| _{idx(src(k))} } \\405 +& \sum_{k=9 }^{12} {wgt(k)\left.\frac{\partial f}{\partial j}\right| _{idx(src(k))} }406 + 375 + \sum_{k=5 }^{8 } {wgt(k)\left.\frac{\partial f}{\partial i}\right| _{idx(src(k))} } \\ 376 +& \sum_{k=9 }^{12} {wgt(k)\left.\frac{\partial f}{\partial j}\right| _{idx(src(k))} } 377 + \sum_{k=13}^{16} {wgt(k)\left.\frac{\partial ^2 f}{\partial i \partial j}\right| _{idx(src(k))} } 407 378 \end{split} 408 379 \] 409 380 The gradients here are taken with respect to the horizontal indices and not distances since 410 the spatial dependency has been absorbed into the weights. 411 381 the spatial dependency has been included into the weights. 382 383 %% ================================================================================================= 412 384 \subsubsection{Implementation} 413 385 \label{subsec:SBC_iof_imp} … … 421 393 inspecting a global attribute stored in the weights input file. 422 394 This attribute must be called "ew\_wrap" and be of integer type. 423 If it is negative, the input non-model grid is assumed not to becyclic.395 If it is negative, the input non-model grid is assumed to be not cyclic. 424 396 If zero or greater, then the value represents the number of columns that overlap. 425 397 $E.g.$ if the input grid has columns at longitudes 0, 1, 2, .... , 359, then ew\_wrap should be set to 0; 426 398 if longitudes are 0.5, 2.5, .... , 358.5, 360.5, 362.5, ew\_wrap should be 2. 427 399 If the model does not find attribute ew\_wrap, then a value of -999 is assumed. 428 In this case the \rou{fld\_read} routine defaults ew\_wrap to value 0 and400 In this case, the \rou{fld\_read} routine defaults ew\_wrap to value 0 and 429 401 therefore the grid is assumed to be cyclic with no overlapping columns. 430 (In fact this only matters when bicubic interpolation is required.)402 (In fact, this only matters when bicubic interpolation is required.) 431 403 Note that no testing is done to check the validity in the model, 432 404 since there is no way of knowing the name used for the longitude variable, … … 445 417 or is a copy of one from the first few columns on the opposite side of the grid (cyclical case). 446 418 419 %% ================================================================================================= 447 420 \subsubsection{Limitations} 448 421 \label{subsec:SBC_iof_lim} 449 422 450 \begin{enumerate} 451 \item 452 The case where input data grids are not logically rectangular has not been tested. 453 \item 454 This code is not guaranteed to produce positive definite answers from positive definite inputs when 423 \begin{enumerate} 424 \item The case where input data grids are not logically rectangular (irregular grid case) has not been tested. 425 \item This code is not guaranteed to produce positive definite answers from positive definite inputs when 455 426 a bicubic interpolation method is used. 456 \item 457 The cyclic condition is only applied on left and right columns, and not to top and bottom rows. 458 \item 459 The gradients across the ends of a cyclical grid assume that the grid spacing between 427 \item The cyclic condition is only applied on left and right columns, and not to top and bottom rows. 428 \item The gradients across the ends of a cyclical grid assume that the grid spacing between 460 429 the two columns involved are consistent with the weights used. 461 \item 462 Neither interpolation scheme is conservative. (There is a conservative scheme available in SCRIP, 430 \item Neither interpolation scheme is conservative. (There is a conservative scheme available in SCRIP, 463 431 but this has not been implemented.) 464 432 \end{enumerate} 465 433 434 %% ================================================================================================= 466 435 \subsubsection{Utilities} 467 436 \label{subsec:SBC_iof_util} … … 471 440 (see the directory NEMOGCM/TOOLS/WEIGHTS). 472 441 473 % ------------------------------------------------------------------------------------------------------------- 474 % Standalone Surface Boundary Condition Scheme 475 % ------------------------------------------------------------------------------------------------------------- 476 \subsection{Standalone surface boundary condition scheme} 477 \label{subsec:SAS_iof} 478 479 %---------------------------------------namsbc_ana-------------------------------------------------- 480 481 \nlst{namsbc_sas} 482 %-------------------------------------------------------------------------------------------------------------- 483 484 In some circumstances it may be useful to avoid calculating the 3D temperature, 485 salinity and velocity fields and simply read them in from a previous run or receive them from OASIS. 442 %% ================================================================================================= 443 \subsection{Standalone surface boundary condition scheme (SAS)} 444 \label{subsec:SBC_SAS} 445 446 \begin{listing} 447 \nlst{namsbc_sas} 448 \caption{\forcode{&namsbc_sas}} 449 \label{lst:namsbc_sas} 450 \end{listing} 451 452 In some circumstances, it may be useful to avoid calculating the 3D temperature, 453 salinity and velocity fields and simply read them in from a previous run or receive them from OASIS. 486 454 For example: 487 455 488 456 \begin{itemize} 489 \item 490 Multiple runs of the model are required in code development to 457 \item Multiple runs of the model are required in code development to 491 458 see the effect of different algorithms in the bulk formulae. 492 \item 493 The effect of different parameter sets in the ice model is to be examined. 494 \item 495 Development of sea-ice algorithms or parameterizations. 496 \item 497 Spinup of the iceberg floats 498 \item 499 Ocean/sea-ice simulation with both media running in parallel (\np{ln\_mixcpl}\forcode{ = .true.}) 459 \item The effect of different parameter sets in the ice model is to be examined. 460 \item Development of sea-ice algorithms or parameterizations. 461 \item Spinup of the iceberg floats 462 \item Ocean/sea-ice simulation with both models running in parallel (\np[=.true.]{ln_mixcpl}{ln\_mixcpl}) 500 463 \end{itemize} 501 464 502 The Stand Alone Surface scheme provides this utility.503 Its options are defined through the \n gn{namsbc\_sas} namelist variables.465 The Standalone Surface scheme provides this capacity. 466 Its options are defined through the \nam{sbc_sas}{sbc\_sas} namelist variables. 504 467 A new copy of the model has to be compiled with a configuration based on ORCA2\_SAS\_LIM. 505 However no namelist parameters need be changed from the settings of the previous run (except perhaps nn{\_}date0).468 However, no namelist parameters need be changed from the settings of the previous run (except perhaps nn\_date0). 506 469 In this configuration, a few routines in the standard model are overriden by new versions. 507 470 Routines replaced are: 508 471 509 472 \begin{itemize} 510 \item 511 \mdl{nemogcm}: 512 This routine initialises the rest of the model and repeatedly calls the stp time stepping routine (\mdl{step}). 473 \item \mdl{nemogcm}: This routine initialises the rest of the model and repeatedly calls the stp time stepping routine (\mdl{step}). 513 474 Since the ocean state is not calculated all associated initialisations have been removed. 514 \item 515 \mdl{step}: 516 The main time stepping routine now only needs to call the sbc routine (and a few utility functions). 517 \item 518 \mdl{sbcmod}: 519 This has been cut down and now only calculates surface forcing and the ice model required. 475 \item \mdl{step}: The main time stepping routine now only needs to call the sbc routine (and a few utility functions). 476 \item \mdl{sbcmod}: This has been cut down and now only calculates surface forcing and the ice model required. 520 477 New surface modules that can function when only the surface level of the ocean state is defined can also be added 521 (\eg icebergs). 522 \item 523 \mdl{daymod}: 524 No ocean restarts are read or written (though the ice model restarts are retained), 478 (\eg\ icebergs). 479 \item \mdl{daymod}: No ocean restarts are read or written (though the ice model restarts are retained), 525 480 so calls to restart functions have been removed. 526 481 This also means that the calendar cannot be controlled by time in a restart file, 527 so the user must make sure that nn{\_}date0 in the model namelist is correct for his or her purposes. 528 \item 529 \mdl{stpctl}: 530 Since there is no free surface solver, references to it have been removed from \rou{stp\_ctl} module. 531 \item 532 \mdl{diawri}: 533 All 3D data have been removed from the output. 482 so the user must check that nn\_date0 in the model namelist is correct for his or her purposes. 483 \item \mdl{stpctl}: Since there is no free surface solver, references to it have been removed from \rou{stp\_ctl} module. 484 \item \mdl{diawri}: All 3D data have been removed from the output. 534 485 The surface temperature, salinity and velocity components (which have been read in) are written along with 535 486 relevant forcing and ice data. … … 539 490 540 491 \begin{itemize} 541 \item 542 \mdl{sbcsas}: 543 This module initialises the input files needed for reading temperature, salinity and 492 \item \mdl{sbcsas}: This module initialises the input files needed for reading temperature, salinity and 544 493 velocity arrays at the surface. 545 These filenames are supplied in namelist namsbc {\_}sas.546 Unfortunately because of limitations with the \mdl{iom} module,494 These filenames are supplied in namelist namsbc\_sas. 495 Unfortunately, because of limitations with the \mdl{iom} module, 547 496 the full 3D fields from the mean files have to be read in and interpolated in time, 548 497 before using just the top level. … … 550 499 \end{itemize} 551 500 552 553 % Missing the description of the 2 following variables: 554 % ln_3d_uve = .true. ! specify whether we are supplying a 3D u,v and e3 field 555 % ln_read_frq = .false. ! specify whether we must read frq or not 556 557 558 559 % ================================================================ 560 % Analytical formulation (sbcana module) 561 % ================================================================ 562 \section[Analytical formulation (\textit{sbcana.F90})] 563 {Analytical formulation (\protect\mdl{sbcana})} 564 \label{sec:SBC_ana} 565 566 %---------------------------------------namsbc_ana-------------------------------------------------- 567 % 568 %\nlst{namsbc_ana} 569 %-------------------------------------------------------------------------------------------------------------- 570 571 The analytical formulation of the surface boundary condition is the default scheme. 572 In this case, all the six fluxes needed by the ocean are assumed to be uniform in space. 573 They take constant values given in the namelist \ngn{namsbc{\_}ana} by 574 the variables \np{rn\_utau0}, \np{rn\_vtau0}, \np{rn\_qns0}, \np{rn\_qsr0}, and \np{rn\_emp0} 575 ($\textit{emp}=\textit{emp}_S$). 576 The runoff is set to zero. 577 In addition, the wind is allowed to reach its nominal value within a given number of time steps (\np{nn\_tau000}). 578 579 If a user wants to apply a different analytical forcing, 580 the \mdl{sbcana} module can be modified to use another scheme. 581 As an example, the \mdl{sbc\_ana\_gyre} routine provides the analytical forcing for the GYRE configuration 582 (see GYRE configuration manual, in preparation). 583 584 585 % ================================================================ 586 % Flux formulation 587 % ================================================================ 588 \section[Flux formulation (\textit{sbcflx.F90})] 589 {Flux formulation (\protect\mdl{sbcflx})} 501 The user can also choose in the \nam{sbc_sas}{sbc\_sas} namelist to read the mean (nn\_fsbc time-step) fraction of solar net radiation absorbed in the 1st T level using 502 (\np[=.true.]{ln_flx}{ln\_flx}) and to provide 3D oceanic velocities instead of 2D ones (\np{ln_flx}{ln\_flx}\forcode{=.true.}). In that last case, only the 1st level will be read in. 503 504 %% ================================================================================================= 505 \section[Flux formulation (\textit{sbcflx.F90})]{Flux formulation (\protect\mdl{sbcflx})} 590 506 \label{sec:SBC_flx} 591 %------------------------------------------namsbc_flx---------------------------------------------------- 592 593 \nlst{namsbc_flx} 594 %------------------------------------------------------------------------------------------------------------- 595 596 In the flux formulation (\np{ln\_flx}\forcode{ = .true.}), 507 508 % Laurent: DO NOT mix up ``bulk formulae'' (the classic equation) and the ``bulk 509 % parameterization'' (i.e NCAR, COARE, ECMWF...) 510 511 \begin{listing} 512 \nlst{namsbc_flx} 513 \caption{\forcode{&namsbc_flx}} 514 \label{lst:namsbc_flx} 515 \end{listing} 516 517 In the flux formulation (\np[=.true.]{ln_flx}{ln\_flx}), 597 518 the surface boundary condition fields are directly read from input files. 598 The user has to define in the namelist \n gn{namsbc{\_}flx} the name of the file,519 The user has to define in the namelist \nam{sbc_flx}{sbc\_flx} the name of the file, 599 520 the name of the variable read in the file, the time frequency at which it is given (in hours), 600 521 and a logical setting whether a time interpolation to the model time step is required for this field. … … 605 526 606 527 607 % ================================================================ 608 % Bulk formulation 609 % ================================================================ 610 \section[Bulk formulation {(\textit{sbcblk\{\_core,\_clio\}.F90})}] 611 {Bulk formulation {(\protect\mdl{sbcblk\_core}, \protect\mdl{sbcblk\_clio})}} 528 529 530 531 532 533 %% ================================================================================================= 534 \pagebreak 535 \newpage 536 \section[Bulk formulation (\textit{sbcblk.F90})]{Bulk formulation (\protect\mdl{sbcblk})} 612 537 \label{sec:SBC_blk} 613 538 614 In the bulk formulation, the surface boundary condition fields are computed using bulk formulae and atmospheric fields and ocean (and ice) variables. 615 616 The atmospheric fields used depend on the bulk formulae used. 617 Two bulk formulations are available: 618 the CORE and the CLIO bulk formulea. 619 The choice is made by setting to true one of the following namelist variable: 620 \np{ln\_core} or \np{ln\_clio}. 621 622 Note: 623 in forced mode, when a sea-ice model is used, a bulk formulation (CLIO or CORE) have to be used. 624 Therefore the two bulk (CLIO and CORE) formulea include the computation of the fluxes over 625 both an ocean and an ice surface. 626 627 % ------------------------------------------------------------------------------------------------------------- 628 % CORE Bulk formulea 629 % ------------------------------------------------------------------------------------------------------------- 630 \subsection[CORE formulea (\textit{sbcblk\_core.F90}, \forcode{ln_core = .true.})] 631 {CORE formulea (\protect\mdl{sbcblk\_core}, \protect\np{ln\_core}\forcode{ = .true.})} 632 \label{subsec:SBC_blk_core} 633 %------------------------------------------namsbc_core---------------------------------------------------- 634 % 635 %\nlst{namsbc_core} 636 %------------------------------------------------------------------------------------------------------------- 637 638 The CORE bulk formulae have been developed by \citet{large.yeager_rpt04}. 639 They have been designed to handle the CORE forcing, a mixture of NCEP reanalysis and satellite data. 640 They use an inertial dissipative method to compute the turbulent transfer coefficients 641 (momentum, sensible heat and evaporation) from the 10 metre wind speed, air temperature and specific humidity. 642 This \citet{large.yeager_rpt04} dataset is available through 643 the \href{http://nomads.gfdl.noaa.gov/nomads/forms/mom4/CORE.html}{GFDL web site}. 644 645 Note that substituting ERA40 to NCEP reanalysis fields does not require changes in the bulk formulea themself. 646 This is the so-called DRAKKAR Forcing Set (DFS) \citep{brodeau.barnier.ea_OM10}. 647 648 Options are defined through the \ngn{namsbc\_core} namelist variables. 649 The required 8 input fields are: 650 651 %--------------------------------------------------TABLE-------------------------------------------------- 539 % L. Brodeau, December 2019... 540 541 \begin{listing} 542 \nlst{namsbc_blk} 543 \caption{\forcode{&namsbc_blk}} 544 \label{lst:namsbc_blk} 545 \end{listing} 546 547 If the bulk formulation is selected (\np[=.true.]{ln_blk}{ln\_blk}), the air-sea 548 fluxes associated with surface boundary conditions are estimated by means of the 549 traditional \emph{bulk formulae}. As input, bulk formulae rely on a prescribed 550 near-surface atmosphere state (typically extracted from a weather reanalysis) 551 and the prognostic sea (-ice) surface state averaged over \np{nn_fsbc}{nn\_fsbc} 552 time-step(s). 553 554 % Turbulent air-sea fluxes are computed using the sea surface properties and 555 % atmospheric SSVs at height $z$ above the sea surface, with the traditional 556 % aerodynamic bulk formulae: 557 558 Note: all the NEMO Fortran routines involved in the present section have been 559 initially developed (and are still developped in parallel) in 560 the \href{https://brodeau.github.io/aerobulk/}{\texttt{AeroBulk}} open-source project 561 \citep{brodeau.barnier.ea_JPO17}. 562 563 %%% Bulk formulae are this: 564 \subsection{Bulk formulae}\label{subsec:SBC_blkform} 565 % 566 In NEMO, the set of equations that relate each component of the surface fluxes 567 to the near-surface atmosphere and sea surface states writes 568 % 569 \begin{subequations}\label{eq_bulk} 570 \begin{eqnarray} 571 \mathbf{\tau} &=& \rho~ C_D ~ \mathbf{U}_z ~ U_B \label{eq_b_t} \\ 572 Q_H &=& \rho~C_H~C_P~\big[ \theta_z - T_s \big] ~ U_B \label{eq_b_qh} \\ 573 E &=& \rho~C_E ~\big[ q_s - q_z \big] ~ U_B \label{eq_b_e} \\ 574 Q_L &=& -L_v \, E \label{eq_b_qe} \\ 575 % 576 Q_{sr} &=& (1 - a) Q_{sw\downarrow} \\ 577 Q_{ir} &=& \delta (Q_{lw\downarrow} -\sigma T_s^4) 578 \end{eqnarray} 579 \end{subequations} 580 % 581 with 582 \[ \theta_z \simeq T_z+\gamma z \] 583 \[ q_s \simeq 0.98\,q_{sat}(T_s,p_a ) \] 584 % 585 from which, the the non-solar heat flux is \[ Q_{ns} = Q_L + Q_H + Q_{ir} \] 586 % 587 where $\mathbf{\tau}$ is the wind stress vector, $Q_H$ the sensible heat flux, 588 $E$ the evaporation, $Q_L$ the latent heat flux, and $Q_{ir}$ the net longwave 589 flux. 590 % 591 $Q_{sw\downarrow}$ and $Q_{lw\downarrow}$ are the surface downwelling shortwave 592 and longwave radiative fluxes, respectively. 593 % 594 Note: a positive sign of $\mathbf{\tau}$, the various fluxes of heat implies a 595 gain of the relevant quantity for the ocean, while a positive $E$ implies a 596 freshwater loss for the ocean. 597 % 598 $\rho$ is the density of air. $C_D$, $C_H$ and $C_E$ are the bulk transfer 599 coefficients for momentum, sensible heat, and moisture, respectively (hereafter 600 referred to as BTCs). 601 % 602 $C_P$ is the heat capacity of moist air, and $L_v$ is the latent heat of 603 vaporization of water. 604 % 605 $\theta_z$, $T_z$ and $q_z$ are the potential temperature, absolute temperature, 606 and specific humidity of air at height $z$ above the sea surface, 607 respectively. $\gamma z$ is a temperature correction term which accounts for the 608 adiabatic lapse rate and approximates the potential temperature at height 609 $z$ \citep{josey.gulev.ea_2013}. 610 % 611 $\mathbf{U}_z$ is the wind speed vector at height $z$ above the sea surface 612 (possibly referenced to the surface current $\mathbf{u_0}$, 613 section \ref{s_res1}.\ref{ss_current}). 614 % 615 The bulk scalar wind speed, namely $U_B$, is the scalar wind speed, 616 $|\mathbf{U}_z|$, with the potential inclusion of a gustiness contribution . 617 % 618 $a$ and $\delta$ are the albedo and emissivity of the sea surface, respectively.\\ 619 % 620 %$p_a$ is the mean sea-level pressure (SLP). 621 % 622 $T_s$ is the sea surface temperature. $q_s$ is the saturation specific humidity 623 of air at temperature $T_s$ and includes a 2\% reduction to account for the 624 presence of salt in seawater \citep{sverdrup.johnson.ea_1942,kraus.businger_QJRMS96}. 625 Depending on the bulk parametrization used, $T_s$ can either be the temperature 626 at the air-sea interface (skin temperature, hereafter SSST) or at typically a 627 few tens of centimeters below the surface (bulk sea surface temperature, 628 hereafter SST). 629 % 630 The SSST differs from the SST due to the contributions of two effects of 631 opposite sign, the \emph{cool skin} and \emph{warm layer} (hereafter CS and WL, 632 respectively, see section\,\ref{subsec:SBC_skin}). 633 % 634 Technically, when the ECMWF or COARE* bulk parametrizations are selected 635 (\np[=.true.]{ln_ECMWF}{ln\_ECMWF} or \np[=.true.]{ln_COARE*}{ln\_COARE\*}), 636 $T_s$ is the SSST, as opposed to the NCAR bulk parametrization 637 (\np[=.true.]{ln_NCAR}{ln\_NCAR}) for which $T_s$ is the bulk SST (\ie~temperature 638 at first T-point level). 639 640 641 For more details on all these aspects the reader is invited to refer 642 to \citet{brodeau.barnier.ea_JPO17}. 643 644 645 646 \subsection{Bulk parametrizations}\label{subsec:SBC_blk_ocean} 647 %%%\label{subsec:SBC_param} 648 649 Accuracy of the estimate of surface turbulent fluxes by means of bulk formulae 650 strongly relies on that of the bulk transfer coefficients: $C_D$, $C_H$ and 651 $C_E$. They are estimated with what we refer to as a \emph{bulk 652 parametrization} algorithm. When relevant, these algorithms also perform the 653 height adjustment of humidity and temperature to the wind reference measurement 654 height (from \np{rn_zqt}{rn\_zqt} to \np{rn_zu}{rn\_zu}). 655 656 657 658 For the open ocean, four bulk parametrization algorithms are available: 659 \begin{itemize} 660 \item NCAR, formerly known as CORE, \citep{large.yeager_rpt04,large.yeager_CD09} 661 \item COARE 3.0 \citep{fairall.bradley.ea_JC03} 662 \item COARE 3.6 \citep{edson.jampana.ea_JPO13} 663 \item ECMWF (IFS documentation, cy45) 664 \end{itemize} 665 666 667 Differences between versions 3.0 and 3.6 of the COARE algorithm mainly ... wind 668 stress BLABLA \citep{edson.jampana.ea_JPO13,brodeau.barnier.ea_JPO17}. 669 Therefore it is recommanded to use version 3.6 of the COARE algorithms rather 670 than version 3. 671 672 673 674 675 \subsection{Cool-skin and warm-layer parametrizations}\label{subsec:SBC_skin} 676 %\subsection[Cool-skin and warm-layer parameterizations 677 %(\forcode{ln_skin_cs} \& \forcode{ln_skin_wl})]{Cool-skin and warm-layer parameterizations (\protect\np{ln_skin_cs}{ln\_skin\_cs} \& \np{ln_skin_wl}{ln\_skin\_wl})} 678 %\label{subsec:SBC_skin} 679 % 680 As opposed to the NCAR bulk parametrization, more advanced bulk 681 parametrizations such as COARE3.x and ECMWF are meant to be used with the skin 682 temperature $T_s$ rather than the bulk SST (which, in NEMO is the temperature at 683 the first T-point level, see section\,\ref{subsec:SBC_blkform}). 684 % 685 As such, the relevant cool-skin and warm-layer parametrization must be 686 activated through \np[=T]{ln_skin_cs}{ln\_skin\_cs} 687 and \np[=T]{ln_skin_wl}{ln\_skin\_wl} to use COARE3.x or ECMWF in a consistent 688 way. 689 690 \texttt{\#LB: ADD BLBLA ABOUT THE TWO CS/WL PARAMETRIZATIONS (ECMWF and COARE) !!!} 691 692 For the cool-skin scheme parametrization COARE and ECMWF algorithms share the same 693 basis: \citet{fairall.bradley.ea_JGR96}. With some minor updates based 694 on \citet{zeng.beljaars_GRL05} for ECMWF, and \citet{fairall.ea_19} for COARE 695 3.6. 696 697 For the warm-layer scheme, ECMWF is based on \citet{zeng.beljaars_GRL05} with a 698 recent update from \citet{takaya.bidlot.ea_JGR10} (consideration of the 699 turbulence input from Langmuir circulation). 700 701 Importantly, COARE warm-layer scheme \citep{fairall.ea_19} includes a prognostic 702 equation for the thickness of the warm-layer, while it is considered as constant 703 in the ECWMF algorithm. 704 705 706 \subsection{Appropriate use of each bulk parametrization} 707 708 \subsubsection{NCAR} 709 710 NCAR bulk parametrizations (formerly know as CORE) is meant to be used with the 711 CORE II atmospheric forcing \citep{large.yeager_CD09}. Hence the following 712 namelist parameters must be set: 713 % 714 \begin{verbatim} 715 ... 716 ln_NCAR = .true. 717 ... 718 rn_zqt = 10. ! Air temperature & humidity reference height (m) 719 rn_zu = 10. ! Wind vector reference height (m) 720 ... 721 ln_skin_cs = .false. ! use the cool-skin parameterization 722 ln_skin_wl = .false. ! use the warm-layer parameterization 723 ... 724 ln_humi_sph = .true. ! humidity "sn_humi" is specific humidity [kg/kg] 725 \end{verbatim} 726 727 728 \subsubsection{ECMWF} 729 % 730 With a DFS* or any ECMWF-based type of atmospheric forcing, we strongly 731 recommend to use the ECMWF bulk parametrizations with the cool-skin and 732 warm-layer parametrizations turned on. In ECMWF reanalyzes, since air 733 temperature and humidity are provided at the 2\,m height, and given that the 734 humidity is provided as the dew-point temperature, the namelist must be tuned as 735 follows: 736 % 737 \begin{verbatim} 738 ... 739 ln_ECMWF = .true. 740 ... 741 rn_zqt = 2. ! Air temperature & humidity reference height (m) 742 rn_zu = 10. ! Wind vector reference height (m) 743 ... 744 ln_skin_cs = .true. ! use the cool-skin parameterization 745 ln_skin_wl = .true. ! use the warm-layer parameterization 746 ... 747 ln_humi_dpt = .true. ! humidity "sn_humi" is dew-point temperature [K] 748 ... 749 \end{verbatim} 750 % 751 Note: when \np{ln_ECMWF}{ln\_ECMWF} is selected, the selection 752 of \np{ln_skin_cs}{ln\_skin\_cs} and \np{ln_skin_wl}{ln\_skin\_wl} implicitly 753 triggers the use of the ECMWF cool-skin and warm-layer parametrizations, 754 respectively (found in \textit{sbcblk\_skin\_ecmwf.F90}). 755 756 757 \subsubsection{COARE 3.x} 758 % 759 Since the ECMWF parametrization is largely based on the COARE* parametrization, 760 the two algorithms are very similar in terms of structure and closure approach 761 (see \citet{brodeau.barnier.ea_JPO17} for the differences). As such, the 762 namelist tuning for COARE 3.x is identical to that of ECMWF: 763 % 764 \begin{verbatim} 765 ... 766 ln_COARE3p6 = .true. 767 ... 768 ln_skin_cs = .true. ! use the cool-skin parameterization 769 ln_skin_wl = .true. ! use the warm-layer parameterization 770 ... 771 \end{verbatim} 772 773 Note: when \np[=T]{ln_COARE3p0}{ln\_COARE3p0} is selected, the selection 774 of \np{ln_skin_cs}{ln\_skin\_cs} and \np{ln_skin_wl}{ln\_skin\_wl} implicitly 775 triggers the use of the COARE cool-skin and warm-layer parametrizations, 776 respectively (found in \textit{sbcblk\_skin\_coare.F90}). 777 778 779 ~ 780 781 782 783 % In a typical bulk algorithm, the BTCs under neutral stability conditions are 784 % defined using \emph{in-situ} flux measurements while their dependence on the 785 % stability is accounted through the \emph{Monin-Obukhov Similarity Theory} and 786 % the \emph{flux-profile} relationships \citep[\eg{}][]{Paulson_1970}. BTCs are 787 % functions of the wind speed and the near-surface stability of the atmospheric 788 % surface layer (hereafter ASL), and hence, depend on $U_B$, $T_s$, $T_z$, $q_s$ 789 % and $q_z$. 790 791 792 793 \subsection{Prescribed near-surface atmospheric state} 794 795 The atmospheric fields used depend on the bulk formulae used. In forced mode, 796 when a sea-ice model is used, a specific bulk formulation is used. Therefore, 797 different bulk formulae are used for the turbulent fluxes computation over the 798 ocean and over sea-ice surface. 799 % 800 801 %The choice is made by setting to true one of the following namelist 802 %variable: \np{ln_NCAR}{ln\_NCAR}, \np{ln_COARE_3p0}{ln\_COARE\_3p0}, \np{ln_COARE_3p6}{ln\_COARE\_3p6} 803 %and \np{ln_ECMWF}{ln\_ECMWF}. 804 805 Common options are defined through the \nam{sbc_blk}{sbc\_blk} namelist variables. 806 The required 9 input fields are: 807 652 808 \begin{table}[htbp] 653 \label{tab:CORE} 654 \begin{center} 655 \begin{tabular}{|l|c|c|c|} 656 \hline 657 Variable desciption & Model variable & Units & point \\ \hline 658 i-component of the 10m air velocity & utau & $m.s^{-1}$ & T \\ \hline 659 j-component of the 10m air velocity & vtau & $m.s^{-1}$ & T \\ \hline 660 10m air temperature & tair & \r{}$K$ & T \\ \hline 661 Specific humidity & humi & \% & T \\ \hline 662 Incoming long wave radiation & qlw & $W.m^{-2}$ & T \\ \hline 663 Incoming short wave radiation & qsr & $W.m^{-2}$ & T \\ \hline 664 Total precipitation (liquid + solid) & precip & $Kg.m^{-2}.s^{-1}$ & T \\ \hline 665 Solid precipitation & snow & $Kg.m^{-2}.s^{-1}$ & T \\ \hline 809 \centering 810 \begin{tabular}{|l|c|c|c|} 811 \hline 812 Variable description & Model variable & Units & point \\ 813 \hline 814 i-component of the 10m air velocity & wndi & $m.s^{-1}$ & T \\ 815 \hline 816 j-component of the 10m air velocity & wndj & $m.s^{-1}$ & T \\ 817 \hline 818 10m air temperature & tair & $K$ & T \\ 819 \hline 820 Specific humidity & humi & $-$ & T \\ 821 Relative humidity & ~ & $\%$ & T \\ 822 Dew-point temperature & ~ & $K$ & T \\ 823 \hline 824 Downwelling longwave radiation & qlw & $W.m^{-2}$ & T \\ 825 \hline 826 Downwelling shortwave radiation & qsr & $W.m^{-2}$ & T \\ 827 \hline 828 Total precipitation (liquid + solid) & precip & $Kg.m^{-2}.s^{-1}$ & T \\ 829 \hline 830 Solid precipitation & snow & $Kg.m^{-2}.s^{-1}$ & T \\ 831 \hline 832 Mean sea-level pressure & slp & $hPa$ & T \\ 833 \hline 666 834 \end{tabular} 667 \ end{center}835 \label{tab:SBC_BULK} 668 836 \end{table} 669 %--------------------------------------------------------------------------------------------------------------670 837 671 838 Note that the air velocity is provided at a tracer ocean point, not at a velocity ocean point ($u$- and $v$-points). … … 673 840 the ocean grid size is the same or larger than the one of the input atmospheric fields. 674 841 675 The \np{sn \_wndi}, \np{sn\_wndj}, \np{sn\_qsr}, \np{sn\_qlw}, \np{sn\_tair}, \np{sn\_humi}, \np{sn\_prec},676 \np{sn \_snow}, \np{sn\_tdif} parameters describe the fields and the way they have to be used677 (spatial and temporal interpolations). 678 679 \np{cn \_dir} is the directory of location of bulk files680 \np{ln \_taudif} is the flag to specify if we use Hight Frequency (HF) tau information (.true.) or not (.false.)681 \np{rn \_zqt}: is the height of humidity and temperature measurements (m)682 \np{rn \_zu}: is the height of wind measurements (m)683 684 Three multiplicative factors are available s:685 \np{rn \_pfac} and \np{rn\_efac} allowsto adjust (if necessary) the global freshwater budget by842 The \np{sn_wndi}{sn\_wndi}, \np{sn_wndj}{sn\_wndj}, \np{sn_qsr}{sn\_qsr}, \np{sn_qlw}{sn\_qlw}, \np{sn_tair}{sn\_tair}, \np{sn_humi}{sn\_humi}, \np{sn_prec}{sn\_prec}, 843 \np{sn_snow}{sn\_snow}, \np{sn_tdif}{sn\_tdif} parameters describe the fields and the way they have to be used 844 (spatial and temporal interpolations). 845 846 \np{cn_dir}{cn\_dir} is the directory of location of bulk files 847 \np{ln_taudif}{ln\_taudif} is the flag to specify if we use Hight Frequency (HF) tau information (.true.) or not (.false.) 848 \np{rn_zqt}{rn\_zqt}: is the height of humidity and temperature measurements (m) 849 \np{rn_zu}{rn\_zu}: is the height of wind measurements (m) 850 851 Three multiplicative factors are available: 852 \np{rn_pfac}{rn\_pfac} and \np{rn_efac}{rn\_efac} allow to adjust (if necessary) the global freshwater budget by 686 853 increasing/reducing the precipitations (total and snow) and or evaporation, respectively. 687 The third one,\np{rn \_vfac}, control to which extend the ice/ocean velocities are taken into account in854 The third one,\np{rn_vfac}{rn\_vfac}, control to which extend the ice/ocean velocities are taken into account in 688 855 the calculation of surface wind stress. 689 Its range should be between zero and one, and it is recommended to set it to 0. 690 691 % ------------------------------------------------------------------------------------------------------------- 692 % CLIO Bulk formulea 693 % ------------------------------------------------------------------------------------------------------------- 694 \subsection[CLIO formulea (\textit{sbcblk\_clio.F90}, \forcode{ln_clio = .true.})] 695 {CLIO formulea (\protect\mdl{sbcblk\_clio}, \protect\np{ln\_clio}\forcode{ = .true.})} 696 \label{subsec:SBC_blk_clio} 697 %------------------------------------------namsbc_clio---------------------------------------------------- 698 % 699 %\nlst{namsbc_clio} 700 %------------------------------------------------------------------------------------------------------------- 701 702 The CLIO bulk formulae were developed several years ago for the Louvain-la-neuve coupled ice-ocean model 703 (CLIO, \cite{goosse.deleersnijder.ea_JGR99}). 704 They are simpler bulk formulae. 705 They assume the stress to be known and compute the radiative fluxes from a climatological cloud cover. 706 707 Options are defined through the \ngn{namsbc\_clio} namelist variables. 708 The required 7 input fields are: 709 710 %--------------------------------------------------TABLE-------------------------------------------------- 711 \begin{table}[htbp] 712 \label{tab:CLIO} 713 \begin{center} 714 \begin{tabular}{|l|l|l|l|} 715 \hline 716 Variable desciption & Model variable & Units & point \\ \hline 717 i-component of the ocean stress & utau & $N.m^{-2}$ & U \\ \hline 718 j-component of the ocean stress & vtau & $N.m^{-2}$ & V \\ \hline 719 Wind speed module & vatm & $m.s^{-1}$ & T \\ \hline 720 10m air temperature & tair & \r{}$K$ & T \\ \hline 721 Specific humidity & humi & \% & T \\ \hline 722 Cloud cover & & \% & T \\ \hline 723 Total precipitation (liquid + solid) & precip & $Kg.m^{-2}.s^{-1}$ & T \\ \hline 724 Solid precipitation & snow & $Kg.m^{-2}.s^{-1}$ & T \\ \hline 725 \end{tabular} 726 \end{center} 727 \end{table} 728 %-------------------------------------------------------------------------------------------------------------- 729 730 As for the flux formulation, information about the input data required by the model is provided in 731 the namsbc\_blk\_core or namsbc\_blk\_clio namelist (see \autoref{subsec:SBC_fldread}). 732 733 % ================================================================ 734 % Coupled formulation 735 % ================================================================ 736 \section[Coupled formulation (\textit{sbccpl.F90})] 737 {Coupled formulation (\protect\mdl{sbccpl})} 856 Its range must be between zero and one, and it is recommended to set it to 0 at low-resolution (ORCA2 configuration). 857 858 As for the flux parameterization, information about the input data required by the model is provided in 859 the namsbc\_blk namelist (see \autoref{subsec:SBC_fldread}). 860 861 862 \subsubsection{Air humidity} 863 864 Air humidity can be provided as three different parameters: specific humidity 865 [kg/kg], relative humidity [\%], or dew-point temperature [K] (LINK to namelist 866 parameters)... 867 868 869 ~\\ 870 871 872 873 874 875 876 877 878 879 880 %% ================================================================================================= 881 %\subsection[Ocean-Atmosphere Bulk formulae (\textit{sbcblk\_algo\_coare3p0.F90, sbcblk\_algo\_coare3p6.F90, %sbcblk\_algo\_ecmwf.F90, sbcblk\_algo\_ncar.F90})]{Ocean-Atmosphere Bulk formulae (\mdl{sbcblk\_algo\_coare3p0}, %\mdl{sbcblk\_algo\_coare3p6}, \mdl{sbcblk\_algo\_ecmwf}, \mdl{sbcblk\_algo\_ncar})} 882 %\label{subsec:SBC_blk_ocean} 883 884 %Four different bulk algorithms are available to compute surface turbulent momentum and heat fluxes over the ocean. 885 %COARE 3.0, COARE 3.6 and ECMWF schemes mainly differ by their roughness lenghts computation and consequently 886 %their neutral transfer coefficients relationships with neutral wind. 887 %\begin{itemize} 888 %\item NCAR (\np[=.true.]{ln_NCAR}{ln\_NCAR}): The NCAR bulk formulae have been developed by \citet{large.yeager_rpt04}. 889 % They have been designed to handle the NCAR forcing, a mixture of NCEP reanalysis and satellite data. 890 % They use an inertial dissipative method to compute the turbulent transfer coefficients 891 % (momentum, sensible heat and evaporation) from the 10m wind speed, air temperature and specific humidity. 892 % This \citet{large.yeager_rpt04} dataset is available through 893 % the \href{http://nomads.gfdl.noaa.gov/nomads/forms/mom4/NCAR.html}{GFDL web site}. 894 % Note that substituting ERA40 to NCEP reanalysis fields does not require changes in the bulk formulea themself. 895 % This is the so-called DRAKKAR Forcing Set (DFS) \citep{brodeau.barnier.ea_OM10}. 896 %\item COARE 3.0 (\np[=.true.]{ln_COARE_3p0}{ln\_COARE\_3p0}): See \citet{fairall.bradley.ea_JC03} for more details 897 %\item COARE 3.6 (\np[=.true.]{ln_COARE_3p6}{ln\_COARE\_3p6}): See \citet{edson.jampana.ea_JPO13} for more details 898 %\item ECMWF (\np[=.true.]{ln_ECMWF}{ln\_ECMWF}): Based on \href{https://www.ecmwf.int/node/9204}{IFS (Cy40r1)} %implementation and documentation. 899 % Surface roughness lengths needed for the Obukhov length are computed 900 % following \citet{beljaars_QJRMS95}. 901 %\end{itemize} 902 903 %% ================================================================================================= 904 \subsection{Ice-Atmosphere Bulk formulae} 905 \label{subsec:SBC_blk_ice} 906 907 908 \texttt{\#out\_of\_place:} 909 For sea-ice, three possibilities can be selected: 910 a constant transfer coefficient (1.4e-3; default 911 value), \citet{lupkes.gryanik.ea_JGR12} (\np{ln_Cd_L12}{ln\_Cd\_L12}), 912 and \citet{lupkes.gryanik_JGR15} (\np{ln_Cd_L15}{ln\_Cd\_L15}) parameterizations 913 \texttt{\#out\_of\_place.} 914 915 916 917 918 Surface turbulent fluxes between sea-ice and the atmosphere can be computed in three different ways: 919 920 \begin{itemize} 921 \item Constant value (\np[ Cd_ice=1.4e-3 ]{constant value}{constant\ value}): 922 default constant value used for momentum and heat neutral transfer coefficients 923 \item \citet{lupkes.gryanik.ea_JGR12} (\np[=.true.]{ln_Cd_L12}{ln\_Cd\_L12}): 924 This scheme adds a dependency on edges at leads, melt ponds and flows 925 of the constant neutral air-ice drag. After some approximations, 926 this can be resumed to a dependency on ice concentration (A). 927 This drag coefficient has a parabolic shape (as a function of ice concentration) 928 starting at 1.5e-3 for A=0, reaching 1.97e-3 for A=0.5 and going down 1.4e-3 for A=1. 929 It is theoretically applicable to all ice conditions (not only MIZ). 930 \item \citet{lupkes.gryanik_JGR15} (\np[=.true.]{ln_Cd_L15}{ln\_Cd\_L15}): 931 Alternative turbulent transfer coefficients formulation between sea-ice 932 and atmosphere with distinct momentum and heat coefficients depending 933 on sea-ice concentration and atmospheric stability (no melt-ponds effect for now). 934 The parameterization is adapted from ECHAM6 atmospheric model. 935 Compared to Lupkes2012 scheme, it considers specific skin and form drags 936 to compute neutral transfer coefficients for both heat and momentum fluxes. 937 Atmospheric stability effect on transfer coefficient is also taken into account. 938 \end{itemize} 939 940 %% ================================================================================================= 941 \section[Coupled formulation (\textit{sbccpl.F90})]{Coupled formulation (\protect\mdl{sbccpl})} 738 942 \label{sec:SBC_cpl} 739 %------------------------------------------namsbc_cpl---------------------------------------------------- 740 741 \nlst{namsbc_cpl} 742 %------------------------------------------------------------------------------------------------------------- 943 944 \begin{listing} 945 \nlst{namsbc_cpl} 946 \caption{\forcode{&namsbc_cpl}} 947 \label{lst:namsbc_cpl} 948 \end{listing} 743 949 744 950 In the coupled formulation of the surface boundary condition, 745 the fluxes are provided by the OASIS coupler at a frequency which is defined in the OASIS coupler ,951 the fluxes are provided by the OASIS coupler at a frequency which is defined in the OASIS coupler namelist, 746 952 while sea and ice surface temperature, ocean and ice albedo, and ocean currents are sent to 747 953 the atmospheric component. 748 954 749 955 A generalised coupled interface has been developed. 750 It is currently interfaced with OASIS-3-MCT (\key{oasis3}). 751 It has been successfully used to interface \NEMO to most of the European atmospheric GCM 956 It is currently interfaced with OASIS-3-MCT versions 1 to 4 (\key{oasis3}). 957 An additional specific CPP key (\key{oa3mct\_v1v2}) is needed for OASIS-3-MCT versions 1 and 2. 958 It has been successfully used to interface \NEMO\ to most of the European atmospheric GCM 752 959 (ARPEGE, ECHAM, ECMWF, HadAM, HadGAM, LMDz), as well as to \href{http://wrf-model.org/}{WRF} 753 960 (Weather Research and Forecasting Model). 754 961 755 Note that in addition to the setting of \np{ln\_cpl} to true, the \key{coupled} have to be defined. 756 The CPP key is mainly used in sea-ice to ensure that the atmospheric fluxes are actually received by 757 the ice-ocean system (no calculation of ice sublimation in coupled mode). 758 When PISCES biogeochemical model (\key{top} and \key{pisces}) is also used in the coupled system, 759 the whole carbon cycle is computed by defining \key{cpl\_carbon\_cycle}. 962 When PISCES biogeochemical model (\key{top}) is also used in the coupled system, 963 the whole carbon cycle is computed. 760 964 In this case, CO$_2$ fluxes will be exchanged between the atmosphere and the ice-ocean system 761 (and need to be activated in \n gn{namsbc{\_}cpl} ).965 (and need to be activated in \nam{sbc_cpl}{sbc\_cpl} ). 762 966 763 967 The namelist above allows control of various aspects of the coupling fields (particularly for vectors) and 764 968 now allows for any coupling fields to have multiple sea ice categories (as required by LIM3 and CICE). 765 When indicating a multi-category coupling field in namsbc{\_}cplthe number of categories will be determined by969 When indicating a multi-category coupling field in \nam{sbc_cpl}{sbc\_cpl}, the number of categories will be determined by 766 970 the number used in the sea ice model. 767 In some limited cases it may be possible to specify single category coupling fields even when971 In some limited cases, it may be possible to specify single category coupling fields even when 768 972 the sea ice model is running with multiple categories - 769 in this case the user should examine the code to be sure the assumptions made are satisfactory. 770 In cases where this is definitely not possible the model should abort with an error message. 771 The new code has been tested using ECHAM with LIM2, and HadGAM3 with CICE but 772 although it will compile with \key{lim3} additional minor code changes may be required to run using LIM3. 773 774 775 % ================================================================ 776 % Atmospheric pressure 777 % ================================================================ 778 \section[Atmospheric pressure (\textit{sbcapr.F90})] 779 {Atmospheric pressure (\protect\mdl{sbcapr})} 973 in this case, the user should examine the code to be sure the assumptions made are satisfactory. 974 In cases where this is definitely not possible, the model should abort with an error message. 975 976 %% ================================================================================================= 977 \section[Atmospheric pressure (\textit{sbcapr.F90})]{Atmospheric pressure (\protect\mdl{sbcapr})} 780 978 \label{sec:SBC_apr} 781 %------------------------------------------namsbc_apr---------------------------------------------------- 782 783 \nlst{namsbc_apr} 784 %------------------------------------------------------------------------------------------------------------- 979 980 \begin{listing} 981 \nlst{namsbc_apr} 982 \caption{\forcode{&namsbc_apr}} 983 \label{lst:namsbc_apr} 984 \end{listing} 785 985 786 986 The optional atmospheric pressure can be used to force ocean and ice dynamics 787 (\np {ln\_apr\_dyn}\forcode{ = .true.}, \textit{\ngn{namsbc}} namelist).788 The input atmospheric forcing defined via \np{sn \_apr} structure (\textit{namsbc\_apr} namelist)987 (\np[=.true.]{ln_apr_dyn}{ln\_apr\_dyn}, \nam{sbc}{sbc} namelist). 988 The input atmospheric forcing defined via \np{sn_apr}{sn\_apr} structure (\nam{sbc_apr}{sbc\_apr} namelist) 789 989 can be interpolated in time to the model time step, and even in space when the interpolation on-the-fly is used. 790 990 When used to force the dynamics, the atmospheric pressure is further transformed into … … 795 995 \] 796 996 where $P_{atm}$ is the atmospheric pressure and $P_o$ a reference atmospheric pressure. 797 A value of $101,000~N/m^2$ is used unless \np{ln \_ref\_apr} is set to true.798 In this case $P_o$ is set to the value of $P_{atm}$ averaged over the ocean domain,799 \ie the mean value of $\eta_{ib}$ is kept to zero at all time step.997 A value of $101,000~N/m^2$ is used unless \np{ln_ref_apr}{ln\_ref\_apr} is set to true. 998 In this case, $P_o$ is set to the value of $P_{atm}$ averaged over the ocean domain, 999 \ie\ the mean value of $\eta_{ib}$ is kept to zero at all time steps. 800 1000 801 1001 The gradient of $\eta_{ib}$ is added to the RHS of the ocean momentum equation (see \mdl{dynspg} for the ocean). 802 1002 For sea-ice, the sea surface height, $\eta_m$, which is provided to the sea ice model is set to $\eta - \eta_{ib}$ 803 1003 (see \mdl{sbcssr} module). 804 $\eta_{ib}$ can be setin the output.1004 $\eta_{ib}$ can be written in the output. 805 1005 This can simplify altimetry data and model comparison as 806 1006 inverse barometer sea surface height is usually removed from these date prior to their distribution. 807 1007 808 1008 When using time-splitting and BDY package for open boundaries conditions, 809 the equivalent inverse barometer sea surface height $\eta_{ib}$ can be added to BDY ssh data: 810 \np{ln\_apr\_obc} might be set to true. 811 812 % ================================================================ 813 % Surface Tides Forcing 814 % ================================================================ 815 \section[Surface tides (\textit{sbctide.F90})] 816 {Surface tides (\protect\mdl{sbctide})} 1009 the equivalent inverse barometer sea surface height $\eta_{ib}$ can be added to BDY ssh data: 1010 \np{ln_apr_obc}{ln\_apr\_obc} might be set to true. 1011 1012 %% ================================================================================================= 1013 \section[Surface tides (\textit{sbctide.F90})]{Surface tides (\protect\mdl{sbctide})} 817 1014 \label{sec:SBC_tide} 818 1015 819 %------------------------------------------nam_tide--------------------------------------- 820 821 \nlst{nam_tide} 822 %----------------------------------------------------------------------------------------- 1016 \begin{listing} 1017 \nlst{nam_tide} 1018 \caption{\forcode{&nam_tide}} 1019 \label{lst:nam_tide} 1020 \end{listing} 823 1021 824 1022 The tidal forcing, generated by the gravity forces of the Earth-Moon and Earth-Sun sytems, 825 is activated if \np{ln \_tide} and \np{ln\_tide\_pot} are both set to \forcode{.true.} in \ngn{nam\_tide}.826 This translates as an additional barotropic force in the momentum equations \ref{eq:PE_dyn} such that:1023 is activated if \np{ln_tide}{ln\_tide} and \np{ln_tide_pot}{ln\_tide\_pot} are both set to \forcode{.true.} in \nam{_tide}{\_tide}. 1024 This translates as an additional barotropic force in the momentum \autoref{eq:MB_PE_dyn} such that: 827 1025 \[ 828 % \label{eq: PE_dyn_tides}1026 % \label{eq:SBC_PE_dyn_tides} 829 1027 \frac{\partial {\mathrm {\mathbf U}}_h }{\partial t}= ... 830 1028 +g\nabla (\Pi_{eq} + \Pi_{sal}) … … 832 1030 where $\Pi_{eq}$ stands for the equilibrium tidal forcing and 833 1031 $\Pi_{sal}$ is a self-attraction and loading term (SAL). 834 1032 835 1033 The equilibrium tidal forcing is expressed as a sum over a subset of 836 1034 constituents chosen from the set of available tidal constituents 837 defined in file \ rou{SBC/tide.h90} (this comprises the tidal1035 defined in file \hf{SBC/tide} (this comprises the tidal 838 1036 constituents \textit{M2, N2, 2N2, S2, K2, K1, O1, Q1, P1, M4, Mf, Mm, 839 1037 Msqm, Mtm, S1, MU2, NU2, L2}, and \textit{T2}). Individual 840 1038 constituents are selected by including their names in the array 841 \np{clname} in \ngn{nam\_tide} (e.g., \np{clname(1) = 'M2',842 clname(2)='S2'} to select solely the tidal consituents \textit{M2}843 and \textit{S2}). Optionally, when \np{ln \_tide\_ramp} is set to1039 \np{clname}{clname} in \nam{_tide}{\_tide} (e.g., \np{clname}{clname}\forcode{(1)='M2', } 1040 \np{clname}{clname}\forcode{(2)='S2'} to select solely the tidal consituents \textit{M2} 1041 and \textit{S2}). Optionally, when \np{ln_tide_ramp}{ln\_tide\_ramp} is set to 844 1042 \forcode{.true.}, the equilibrium tidal forcing can be ramped up 845 linearly from zero during the initial \np{rdttideramp} days of the1043 linearly from zero during the initial \np{rdttideramp}{rdttideramp} days of the 846 1044 model run. 847 1045 … … 850 1048 discussion about the practical implementation of this term). 851 1049 Nevertheless, the complex calculations involved would make this 852 computationally too expensive. 1050 computationally too expensive. Here, two options are available: 853 1051 $\Pi_{sal}$ generated by an external model can be read in 854 (\np {ln\_read\_load=.true.}), or a ``scalar approximation'' can be855 used (\np {ln\_scal\_load=.true.}). In the latter case1052 (\np[=.true.]{ln_read_load}{ln\_read\_load}), or a ``scalar approximation'' can be 1053 used (\np[=.true.]{ln_scal_load}{ln\_scal\_load}). In the latter case 856 1054 \[ 857 1055 \Pi_{sal} = \beta \eta, 858 1056 \] 859 where $\beta$ (\np{rn \_scal\_load} with a default value of 0.094) is a1057 where $\beta$ (\np{rn_scal_load}{rn\_scal\_load} with a default value of 0.094) is a 860 1058 spatially constant scalar, often chosen to minimize tidal prediction 861 errors. Setting both \np{ln \_read\_load} and \np{ln\_scal\_load} to1059 errors. Setting both \np{ln_read_load}{ln\_read\_load} and \np{ln_scal_load}{ln\_scal\_load} to 862 1060 \forcode{.false.} removes the SAL contribution. 863 1061 864 % ================================================================ 865 % River runoffs 866 % ================================================================ 867 \section[River runoffs (\textit{sbcrnf.F90})] 868 {River runoffs (\protect\mdl{sbcrnf})} 1062 %% ================================================================================================= 1063 \section[River runoffs (\textit{sbcrnf.F90})]{River runoffs (\protect\mdl{sbcrnf})} 869 1064 \label{sec:SBC_rnf} 870 %------------------------------------------namsbc_rnf---------------------------------------------------- 871 872 \nlst{namsbc_rnf} 873 %------------------------------------------------------------------------------------------------------------- 874 875 %River runoff generally enters the ocean at a nonzero depth rather than through the surface. 1065 1066 \begin{listing} 1067 \nlst{namsbc_rnf} 1068 \caption{\forcode{&namsbc_rnf}} 1069 \label{lst:namsbc_rnf} 1070 \end{listing} 1071 1072 %River runoff generally enters the ocean at a nonzero depth rather than through the surface. 876 1073 %Many models, however, have traditionally inserted river runoff to the top model cell. 877 %This was the case in \NEMO prior to the version 3.3. The switch toward a input of runoff878 %throughout a nonzero depth has been motivated by the numerical and physical problems 879 %that arise when the top grid cells are of the order of one meter. This situation is common in 880 %coastal modelling and becomes more and more often open ocean and climate modelling 1074 %This was the case in \NEMO\ prior to the version 3.3. The switch toward a input of runoff 1075 %throughout a nonzero depth has been motivated by the numerical and physical problems 1076 %that arise when the top grid cells are of the order of one meter. This situation is common in 1077 %coastal modelling and becomes more and more often open ocean and climate modelling 881 1078 %\footnote{At least a top cells thickness of 1~meter and a 3 hours forcing frequency are 882 1079 %required to properly represent the diurnal cycle \citep{bernie.woolnough.ea_JC05}. see also \autoref{fig:SBC_dcy}.}. 883 1080 884 885 %To do this we need to treat evaporation/precipitation fluxes and river runoff differently in the 886 %\mdl{tra\_sbc} module. We decided to separate them throughout the code, so that the variable 887 %\textit{emp} represented solely evaporation minus precipitation fluxes, and a new 2d variable 888 %rnf was added which represents the volume flux of river runoff (in kg/m2s to remain consistent with 889 %emp). This meant many uses of emp and emps needed to be changed, a list of all modules which use 1081 %To do this we need to treat evaporation/precipitation fluxes and river runoff differently in the 1082 %\mdl{tra\_sbc} module. We decided to separate them throughout the code, so that the variable 1083 %\textit{emp} represented solely evaporation minus precipitation fluxes, and a new 2d variable 1084 %rnf was added which represents the volume flux of river runoff (in kg/m2s to remain consistent with 1085 %emp). This meant many uses of emp and emps needed to be changed, a list of all modules which use 890 1086 %emp or emps and the changes made are below: 891 892 1087 893 1088 %Rachel: 894 1089 River runoff generally enters the ocean at a nonzero depth rather than through the surface. 895 1090 Many models, however, have traditionally inserted river runoff to the top model cell. 896 This was the case in \NEMO prior to the version 3.3,1091 This was the case in \NEMO\ prior to the version 3.3, 897 1092 and was combined with an option to increase vertical mixing near the river mouth. 898 1093 899 1094 However, with this method numerical and physical problems arise when the top grid cells are of the order of one meter. 900 This situation is common in coastal modelling and is becoming more common in open ocean and climate modelling 1095 This situation is common in coastal modelling and is becoming more common in open ocean and climate modelling 901 1096 \footnote{ 902 1097 At least a top cells thickness of 1~meter and a 3 hours forcing frequency are required to … … 909 1104 along with the depth (in metres) which the river should be added to. 910 1105 911 Namelist variables in \n gn{namsbc\_rnf}, \np{ln\_rnf\_depth}, \np{ln\_rnf\_sal} and912 \np{ln \_rnf\_temp} control whether the river attributes (depth, salinity and temperature) are read in and used.1106 Namelist variables in \nam{sbc_rnf}{sbc\_rnf}, \np{ln_rnf_depth}{ln\_rnf\_depth}, \np{ln_rnf_sal}{ln\_rnf\_sal} and 1107 \np{ln_rnf_temp}{ln\_rnf\_temp} control whether the river attributes (depth, salinity and temperature) are read in and used. 913 1108 If these are set as false the river is added to the surface box only, assumed to be fresh (0~psu), 914 1109 and/or taken as surface temperature respectively. 915 1110 916 The runoff value and attributes are read in in sbcrnf. 1111 The runoff value and attributes are read in in sbcrnf. 917 1112 For temperature -999 is taken as missing data and the river temperature is taken to 918 1113 be the surface temperatue at the river point. 919 For the depth parameter a value of -1 means the river is added to the surface box only, 920 and a value of -999 means the river is added through the entire water column. 1114 For the depth parameter a value of -1 means the river is added to the surface box only, 1115 and a value of -999 means the river is added through the entire water column. 921 1116 After being read in the temperature and salinity variables are multiplied by the amount of runoff 922 1117 (converted into m/s) to give the heat and salt content of the river runoff. 923 1118 After the user specified depth is read ini, 924 the number of grid boxes this corresponds to is calculated and stored in the variable \np{nz \_rnf}.1119 the number of grid boxes this corresponds to is calculated and stored in the variable \np{nz_rnf}{nz\_rnf}. 925 1120 The variable \textit{h\_dep} is then calculated to be the depth (in metres) of 926 1121 the bottom of the lowest box the river water is being added to 927 (\ie the total depth that river water is being added to in the model).1122 (\ie\ the total depth that river water is being added to in the model). 928 1123 929 1124 The mass/volume addition due to the river runoff is, at each relevant depth level, added to … … 931 1126 This increases the diffusion term in the vicinity of the river, thereby simulating a momentum flux. 932 1127 The sea surface height is calculated using the sum of the horizontal divergence terms, 933 and so the river runoff indirectly forces an increase in sea surface height. 1128 and so the river runoff indirectly forces an increase in sea surface height. 934 1129 935 1130 The \textit{hdivn} terms are used in the tracer advection modules to force vertical velocities. … … 944 1139 As such the volume of water does not change, but the water is diluted. 945 1140 946 For the non-linear free surface case (\key{vvl}), no flux is allowed through the surface.1141 For the non-linear free surface case, no flux is allowed through the surface. 947 1142 Instead in the surface box (as well as water moving up from the boxes below) a volume of runoff water is added with 948 1143 no corresponding heat and salt addition and so as happens in the lower boxes there is a dilution effect. … … 953 1148 This is done in the same way for both vvl and non-vvl. 954 1149 The temperature and salinity are increased through the specified depth according to 955 the heat and salt content of the river. 1150 the heat and salt content of the river. 956 1151 957 1152 In the non-linear free surface case (vvl), … … 962 1157 963 1158 It is also possible for runnoff to be specified as a negative value for modelling flow through straits, 964 \ie modelling the Baltic flow in and out of the North Sea.1159 \ie\ modelling the Baltic flow in and out of the North Sea. 965 1160 When the flow is out of the domain there is no change in temperature and salinity, 966 1161 regardless of the namelist options used, 967 as the ocean water leaving the domain removes heat and salt (at the same concentration) with it. 968 969 970 %\colorbox{yellow}{Nevertheless, Pb of vertical resolution and 3D input : increase vertical mixing near river mouths to mimic a 3D river 1162 as the ocean water leaving the domain removes heat and salt (at the same concentration) with it. 1163 1164 %\colorbox{yellow}{Nevertheless, Pb of vertical resolution and 3D input : increase vertical mixing near river mouths to mimic a 3D river 971 1165 972 1166 %All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and at the same temperature as the sea surface.} … … 978 1172 %ENDIF 979 1173 980 %\gmcomment{ word doc of runoffs: 981 % 982 %In the current \NEMO setup river runoff is added to emp fluxes, these are then applied at just the sea surface as a volume change (in the variable volume case this is a literal volume change, and in the linear free surface case the free surface is moved) and a salt flux due to the concentration/dilution effect. There is also an option to increase vertical mixing near river mouths; this gives the effect of having a 3d river. All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and at the same temperature as the sea surface. 983 %Our aim was to code the option to specify the temperature and salinity of river runoff, (as well as the amount), along with the depth that the river water will affect. This would make it possible to model low salinity outflow, such as the Baltic, and would allow the ocean temperature to be affected by river runoff. 984 985 %The depth option makes it possible to have the river water affecting just the surface layer, throughout depth, or some specified point in between. 986 987 %To do this we need to treat evaporation/precipitation fluxes and river runoff differently in the tra_sbc module. We decided to separate them throughout the code, so that the variable emp represented solely evaporation minus precipitation fluxes, and a new 2d variable rnf was added which represents the volume flux of river runoff (in kg/m2s to remain consistent with emp). This meant many uses of emp and emps needed to be changed, a list of all modules which use emp or emps and the changes made are below: 988 989 %} 990 % ================================================================ 991 % Ice shelf melting 992 % ================================================================ 993 \section[Ice shelf melting (\textit{sbcisf.F90})] 994 {Ice shelf melting (\protect\mdl{sbcisf})} 1174 \cmtgm{ word doc of runoffs: 1175 In the current \NEMO\ setup river runoff is added to emp fluxes, 1176 these are then applied at just the sea surface as a volume change (in the variable volume case 1177 this is a literal volume change, and in the linear free surface case the free surface is moved) 1178 and a salt flux due to the concentration/dilution effect. 1179 There is also an option to increase vertical mixing near river mouths; 1180 this gives the effect of having a 3d river. 1181 All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and 1182 at the same temperature as the sea surface. 1183 Our aim was to code the option to specify the temperature and salinity of river runoff, 1184 (as well as the amount), along with the depth that the river water will affect. 1185 This would make it possible to model low salinity outflow, such as the Baltic, 1186 and would allow the ocean temperature to be affected by river runoff. 1187 1188 The depth option makes it possible to have the river water affecting just the surface layer, 1189 throughout depth, or some specified point in between. 1190 1191 To do this we need to treat evaporation/precipitation fluxes and river runoff differently in 1192 the \mdl{tra_sbc} module. 1193 We decided to separate them throughout the code, 1194 so that the variable emp represented solely evaporation minus precipitation fluxes, 1195 and a new 2d variable rnf was added which represents the volume flux of river runoff 1196 (in $kg/m^2s$ to remain consistent with $emp$). 1197 This meant many uses of emp and emps needed to be changed, 1198 a list of all modules which use $emp$ or $emps$ and the changes made are below:} 1199 1200 %% ================================================================================================= 1201 \section[Ice shelf melting (\textit{sbcisf.F90})]{Ice shelf melting (\protect\mdl{sbcisf})} 995 1202 \label{sec:SBC_isf} 996 %------------------------------------------namsbc_isf---------------------------------------------------- 997 998 \nlst{namsbc_isf} 999 %-------------------------------------------------------------------------------------------------------- 1000 The namelist variable in \ngn{namsbc}, \np{nn\_isf}, controls the ice shelf representation. 1001 Description and result of sensitivity test to \np{nn\_isf} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1203 1204 \begin{listing} 1205 \nlst{namsbc_isf} 1206 \caption{\forcode{&namsbc_isf}} 1207 \label{lst:namsbc_isf} 1208 \end{listing} 1209 1210 The namelist variable in \nam{sbc}{sbc}, \np{nn_isf}{nn\_isf}, controls the ice shelf representation. 1211 Description and result of sensitivity test to \np{nn_isf}{nn\_isf} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1002 1212 The different options are illustrated in \autoref{fig:SBC_isf}. 1003 1213 1004 1214 \begin{description} 1005 \item[\np{nn\_isf}\forcode{ = 1}]: 1006 The ice shelf cavity is represented (\np{ln\_isfcav}\forcode{ = .true.} needed). 1215 \item [{\np[=1]{nn_isf}{nn\_isf}}]: The ice shelf cavity is represented (\np[=.true.]{ln_isfcav}{ln\_isfcav} needed). 1007 1216 The fwf and heat flux are depending of the local water properties. 1217 1008 1218 Two different bulk formulae are available: 1009 1219 1010 \begin{description} 1011 \item[\np{nn\_isfblk}\forcode{ = 1}]: 1012 The melt rate is based on a balance between the upward ocean heat flux and 1013 the latent heat flux at the ice shelf base. A complete description is available in \citet{hunter_rpt06}. 1014 \item[\np{nn\_isfblk}\forcode{ = 2}]: 1015 The melt rate and the heat flux are based on a 3 equations formulation 1016 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 1017 A complete description is available in \citet{jenkins_JGR91}. 1018 \end{description} 1019 1020 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1021 Its thickness is defined by \np{rn\_hisf\_tbl}. 1022 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn\_hisf\_tbl} m. 1023 Then, the fluxes are spread over the same thickness (ie over one or several cells). 1024 If \np{rn\_hisf\_tbl} larger than top $e_{3}t$, there is no more feedback between the freezing point at the interface and the the top cell temperature. 1025 This can lead to super-cool temperature in the top cell under melting condition. 1026 If \np{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 1027 1028 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1029 There are 3 different ways to compute the exchange coeficient: 1030 \begin{description} 1031 \item[\np{nn\_gammablk}\forcode{ = 0}]: 1032 The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}. 1033 \[ 1034 % \label{eq:sbc_isf_gamma_iso} 1035 \gamma^{T} = \np{rn\_gammat0} 1036 \] 1037 \[ 1038 \gamma^{S} = \np{rn\_gammas0} 1039 \] 1040 This is the recommended formulation for ISOMIP. 1041 \item[\np{nn\_gammablk}\forcode{ = 1}]: 1042 The salt and heat exchange coefficients are velocity dependent and defined as 1043 \[ 1044 \gamma^{T} = \np{rn\_gammat0} \times u_{*} 1045 \] 1046 \[ 1047 \gamma^{S} = \np{rn\_gammas0} \times u_{*} 1048 \] 1049 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters). 1050 See \citet{jenkins.nicholls.ea_JPO10} for all the details on this formulation. It is the recommended formulation for realistic application. 1051 \item[\np{nn\_gammablk}\forcode{ = 2}]: 1052 The salt and heat exchange coefficients are velocity and stability dependent and defined as: 1053 \[ 1054 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1055 \] 1056 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters), 1057 $\Gamma_{Turb}$ the contribution of the ocean stability and 1058 $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 1059 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1060 This formulation has not been extensively tested in NEMO (not recommended). 1061 \end{description} 1062 \item[\np{nn\_isf}\forcode{ = 2}]: 1063 The ice shelf cavity is not represented. 1064 The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 1065 The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 1066 (\np{sn\_depmax\_isf}) and the base of the ice shelf along the calving front 1067 (\np{sn\_depmin\_isf}) as in (\np{nn\_isf}\forcode{ = 3}). 1068 The effective melting length (\np{sn\_Leff\_isf}) is read from a file. 1069 \item[\np{nn\_isf}\forcode{ = 3}]: 1070 The ice shelf cavity is not represented. 1071 The fwf (\np{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between 1072 the depth of the average grounding line (GL) (\np{sn\_depmax\_isf}) and 1073 the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}). 1074 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1075 \item[\np{nn\_isf}\forcode{ = 4}]: 1076 The ice shelf cavity is opened (\np{ln\_isfcav}\forcode{ = .true.} needed). 1077 However, the fwf is not computed but specified from file \np{sn\_fwfisf}). 1078 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1079 As in \np{nn\_isf}\forcode{ = 1}, the fluxes are spread over the top boundary layer thickness (\np{rn\_hisf\_tbl})\\ 1220 \begin{description} 1221 \item [{\np[=1]{nn_isfblk}{nn\_isfblk}}]: The melt rate is based on a balance between the upward ocean heat flux and 1222 the latent heat flux at the ice shelf base. A complete description is available in \citet{hunter_rpt06}. 1223 \item [{\np[=2]{nn_isfblk}{nn\_isfblk}}]: The melt rate and the heat flux are based on a 3 equations formulation 1224 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 1225 A complete description is available in \citet{jenkins_JGR91}. 1226 \end{description} 1227 1228 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1229 Its thickness is defined by \np{rn_hisf_tbl}{rn\_hisf\_tbl}. 1230 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn_hisf_tbl}{rn\_hisf\_tbl} m. 1231 Then, the fluxes are spread over the same thickness (ie over one or several cells). 1232 If \np{rn_hisf_tbl}{rn\_hisf\_tbl} larger than top $e_{3}t$, there is no more feedback between the freezing point at the interface and the the top cell temperature. 1233 This can lead to super-cool temperature in the top cell under melting condition. 1234 If \np{rn_hisf_tbl}{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 1235 1236 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1237 There are 3 different ways to compute the exchange coeficient: 1238 \begin{description} 1239 \item [{\np[=0]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are constant and defined by \np{rn_gammas0}{rn\_gammas0} and \np{rn_gammat0}{rn\_gammat0}. 1240 \begin{gather*} 1241 % \label{eq:SBC_isf_gamma_iso} 1242 \gamma^{T} = rn\_gammat0 \\ 1243 \gamma^{S} = rn\_gammas0 1244 \end{gather*} 1245 This is the recommended formulation for ISOMIP. 1246 \item [{\np[=1]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity dependent and defined as 1247 \begin{gather*} 1248 \gamma^{T} = rn\_gammat0 \times u_{*} \\ 1249 \gamma^{S} = rn\_gammas0 \times u_{*} 1250 \end{gather*} 1251 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters). 1252 See \citet{jenkins.nicholls.ea_JPO10} for all the details on this formulation. It is the recommended formulation for realistic application. 1253 \item [{\np[=2]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity and stability dependent and defined as: 1254 \[ 1255 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1256 \] 1257 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters), 1258 $\Gamma_{Turb}$ the contribution of the ocean stability and 1259 $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 1260 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1261 This formulation has not been extensively tested in \NEMO\ (not recommended). 1262 \end{description} 1263 \item [{\np[=2]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 1264 The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 1265 The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 1266 (\np{sn_depmax_isf}{sn\_depmax\_isf}) and the base of the ice shelf along the calving front 1267 (\np{sn_depmin_isf}{sn\_depmin\_isf}) as in (\np[=3]{nn_isf}{nn\_isf}). 1268 The effective melting length (\np{sn_Leff_isf}{sn\_Leff\_isf}) is read from a file. 1269 \item [{\np[=3]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 1270 The fwf (\np{sn_rnfisf}{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between 1271 the depth of the average grounding line (GL) (\np{sn_depmax_isf}{sn\_depmax\_isf}) and 1272 the base of the ice shelf along the calving front (\np{sn_depmin_isf}{sn\_depmin\_isf}). 1273 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1274 \item [{\np[=4]{nn_isf}{nn\_isf}}]: The ice shelf cavity is opened (\np[=.true.]{ln_isfcav}{ln\_isfcav} needed). 1275 However, the fwf is not computed but specified from file \np{sn_fwfisf}{sn\_fwfisf}). 1276 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1277 As in \np[=1]{nn_isf}{nn\_isf}, the fluxes are spread over the top boundary layer thickness (\np{rn_hisf_tbl}{rn\_hisf\_tbl}) 1080 1278 \end{description} 1081 1279 1082 $\bullet$ \np {nn\_isf}\forcode{ = 1} and \np{nn\_isf}\forcode{ = 2} compute a melt rate based on1280 $\bullet$ \np[=1]{nn_isf}{nn\_isf} and \np[=2]{nn_isf}{nn\_isf} compute a melt rate based on 1083 1281 the water mass properties, ocean velocities and depth. 1084 1282 This flux is thus highly dependent of the model resolution (horizontal and vertical), 1085 1283 realism of the water masses onto the shelf ...\\ 1086 1284 1087 $\bullet$ \np {nn\_isf}\forcode{ = 3} and \np{nn\_isf}\forcode{ = 4} read the melt rate from a file.1285 $\bullet$ \np[=3]{nn_isf}{nn\_isf} and \np[=4]{nn_isf}{nn\_isf} read the melt rate from a file. 1088 1286 You have total control of the fwf forcing. 1089 1287 This can be useful if the water masses on the shelf are not realistic or 1090 1288 the resolution (horizontal/vertical) are too coarse to have realistic melting or 1091 for studies where you need to control your heat and fw input.\\ 1289 for studies where you need to control your heat and fw input.\\ 1092 1290 1093 1291 The ice shelf melt is implemented as a volume flux as for the runoff. … … 1096 1294 See the runoff section \autoref{sec:SBC_rnf} for all the details about the divergence correction.\\ 1097 1295 1098 %>>>>>>>>>>>>>>>>>>>>>>>>>>>>1099 1296 \begin{figure}[!t] 1100 \begin{center} 1101 \includegraphics[width=\textwidth]{Fig_SBC_isf} 1102 \caption{ 1103 \protect\label{fig:SBC_isf} 1104 Illustration the location where the fwf is injected and whether or not the fwf is interactif or not depending of \np{nn\_isf}. 1105 } 1106 \end{center} 1297 \centering 1298 \includegraphics[width=0.66\textwidth]{SBC_isf} 1299 \caption[Ice shelf location and fresh water flux definition]{ 1300 Illustration of the location where the fwf is injected and 1301 whether or not the fwf is interactif or not depending of \protect\np{nn_isf}{nn\_isf}.} 1302 \label{fig:SBC_isf} 1107 1303 \end{figure} 1108 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1109 1304 1305 %% ================================================================================================= 1110 1306 \section{Ice sheet coupling} 1111 1307 \label{sec:SBC_iscpl} 1112 %------------------------------------------namsbc_iscpl---------------------------------------------------- 1113 1114 \nlst{namsbc_iscpl} 1115 %-------------------------------------------------------------------------------------------------------- 1308 1309 \begin{listing} 1310 \nlst{namsbc_iscpl} 1311 \caption{\forcode{&namsbc_iscpl}} 1312 \label{lst:namsbc_iscpl} 1313 \end{listing} 1314 1116 1315 Ice sheet/ocean coupling is done through file exchange at the restart step. 1117 1316 At each restart step: 1118 \begin{description} 1119 \item[Step 1]: the ice sheet model send a new bathymetry and ice shelf draft netcdf file. 1120 \item[Step 2]: a new domcfg.nc file is built using the DOMAINcfg tools. 1121 \item[Step 3]: NEMO run for a specific period and output the average melt rate over the period. 1122 \item[Step 4]: the ice sheet model run using the melt rate outputed in step 4. 1123 \item[Step 5]: go back to 1. 1124 \end{description} 1125 1126 If \np{ln\_iscpl}\forcode{ = .true.}, the isf draft is assume to be different at each restart step with 1317 1318 \begin{enumerate} 1319 \item the ice sheet model send a new bathymetry and ice shelf draft netcdf file. 1320 \item a new domcfg.nc file is built using the DOMAINcfg tools. 1321 \item \NEMO\ run for a specific period and output the average melt rate over the period. 1322 \item the ice sheet model run using the melt rate outputed in step 4. 1323 \item go back to 1. 1324 \end{enumerate} 1325 1326 If \np[=.true.]{ln_iscpl}{ln\_iscpl}, the isf draft is assume to be different at each restart step with 1127 1327 potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics. 1128 1328 The wetting and drying scheme applied on the restart is very simple and described below for the 6 different possible cases: 1329 1129 1330 \begin{description} 1130 \item[Thin a cell down]: 1131 T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant 1331 \item [Thin a cell down]: T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant 1132 1332 ($bt_b=bt_n$). 1133 \item[Enlarge a cell]: 1134 See case "Thin a cell down" 1135 \item[Dry a cell]: 1136 mask, T/S, U/V and ssh are set to 0. 1333 \item [Enlarge a cell]: See case "Thin a cell down" 1334 \item [Dry a cell]: mask, T/S, U/V and ssh are set to 0. 1137 1335 Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1138 \item[Wet a cell]: 1139 mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$ and U/V set to 0. 1140 If no neighbours, T/S is extrapolated from old top cell value. 1336 \item [Wet a cell]: mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$ and U/V set to 0. 1337 If no neighbours, T/S is extrapolated from old top cell value. 1141 1338 If no neighbours along i,j and k (both previous test failed), T/S/U/V/ssh and mask are set to 0. 1142 \item[Dry a column]: 1143 mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0. 1144 \item[Wet a column]: 1145 set mask to 1, T/S is extrapolated from neighbours, ssh is extrapolated from neighbours and U/V set to 0. 1339 \item [Dry a column]: mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0. 1340 \item [Wet a column]: set mask to 1, T/S is extrapolated from neighbours, ssh is extrapolated from neighbours and U/V set to 0. 1146 1341 If no neighbour, T/S/U/V and mask set to 0. 1147 1342 \end{description} … … 1150 1345 the restart time step is prescribed to be an euler time step instead of a leap frog and $fields_b = fields_n$.\\ 1151 1346 1152 The horizontal extrapolation to fill new cell with realistic value is called \np{nn \_drown} times.1153 It means that if the grounding line retreat by more than \np{nn \_drown} cells between 2 coupling steps,1347 The horizontal extrapolation to fill new cell with realistic value is called \np{nn_drown}{nn\_drown} times. 1348 It means that if the grounding line retreat by more than \np{nn_drown}{nn\_drown} cells between 2 coupling steps, 1154 1349 the code will be unable to fill all the new wet cells properly. 1155 1350 The default number is set up for the MISOMIP idealised experiments. 1156 1351 This coupling procedure is able to take into account grounding line and calving front migration. 1157 However, it is a non-conservative processe. 1352 However, it is a non-conservative processe. 1158 1353 This could lead to a trend in heat/salt content and volume.\\ 1159 1354 1160 1355 In order to remove the trend and keep the conservation level as close to 0 as possible, 1161 a simple conservation scheme is available with \np {ln\_hsb}\forcode{ = .true.}.1356 a simple conservation scheme is available with \np[=.true.]{ln_hsb}{ln\_hsb}. 1162 1357 The heat/salt/vol. gain/loss is diagnosed, as well as the location. 1163 A correction increment is computed and apply each time step during the next \np{rn \_fiscpl} time steps.1164 For safety, it is advised to set \np{rn \_fiscpl} equal to the coupling period (smallest increment possible).1358 A correction increment is computed and apply each time step during the next \np{rn_fiscpl}{rn\_fiscpl} time steps. 1359 For safety, it is advised to set \np{rn_fiscpl}{rn\_fiscpl} equal to the coupling period (smallest increment possible). 1165 1360 The corrective increment is apply into the cell itself (if it is a wet cell), the neigbouring cells or the closest wet cell (if the cell is now dry). 1166 1361 1167 % 1168 % ================================================================ 1169 % Handling of icebergs 1170 % ================================================================ 1362 %% ================================================================================================= 1171 1363 \section{Handling of icebergs (ICB)} 1172 \label{sec:ICB_icebergs} 1173 %------------------------------------------namberg---------------------------------------------------- 1174 1175 \nlst{namberg} 1176 %------------------------------------------------------------------------------------------------------------- 1177 1178 Icebergs are modelled as lagrangian particles in NEMO \citep{marsh.ivchenko.ea_GMD15}. 1364 \label{sec:SBC_ICB_icebergs} 1365 1366 \begin{listing} 1367 \nlst{namberg} 1368 \caption{\forcode{&namberg}} 1369 \label{lst:namberg} 1370 \end{listing} 1371 1372 Icebergs are modelled as lagrangian particles in \NEMO\ \citep{marsh.ivchenko.ea_GMD15}. 1179 1373 Their physical behaviour is controlled by equations as described in \citet{martin.adcroft_OM10} ). 1180 (Note that the authors kindly provided a copy of their code to act as a basis for implementation in NEMO).1374 (Note that the authors kindly provided a copy of their code to act as a basis for implementation in \NEMO). 1181 1375 Icebergs are initially spawned into one of ten classes which have specific mass and thickness as 1182 described in the \n gn{namberg} namelist: \np{rn\_initial\_mass} and \np{rn\_initial\_thickness}.1183 Each class has an associated scaling (\np{rn \_mass\_scaling}),1376 described in the \nam{berg}{berg} namelist: \np{rn_initial_mass}{rn\_initial\_mass} and \np{rn_initial_thickness}{rn\_initial\_thickness}. 1377 Each class has an associated scaling (\np{rn_mass_scaling}{rn\_mass\_scaling}), 1184 1378 which is an integer representing how many icebergs of this class are being described as one lagrangian point 1185 1379 (this reduces the numerical problem of tracking every single iceberg). 1186 They are enabled by setting \np {ln\_icebergs}\forcode{ = .true.}.1380 They are enabled by setting \np[=.true.]{ln_icebergs}{ln\_icebergs}. 1187 1381 1188 1382 Two initialisation schemes are possible. 1189 1383 \begin{description} 1190 \item[\np{nn\_test\_icebergs}~$>$~0] 1191 In this scheme, the value of \np{nn\_test\_icebergs} represents the class of iceberg to generate 1192 (so between 1 and 10), and \np{nn\_test\_icebergs} provides a lon/lat box in the domain at each grid point of 1384 \item [{\np{nn_test_icebergs}{nn\_test\_icebergs}~$>$~0}] In this scheme, the value of \np{nn_test_icebergs}{nn\_test\_icebergs} represents the class of iceberg to generate 1385 (so between 1 and 10), and \np{nn_test_icebergs}{nn\_test\_icebergs} provides a lon/lat box in the domain at each grid point of 1193 1386 which an iceberg is generated at the beginning of the run. 1194 (Note that this happens each time the timestep equals \np{nn \_nit000}.)1195 \np{nn \_test\_icebergs} is defined by four numbers in \np{nn\_test\_box} representing the corners of1387 (Note that this happens each time the timestep equals \np{nn_nit000}{nn\_nit000}.) 1388 \np{nn_test_icebergs}{nn\_test\_icebergs} is defined by four numbers in \np{nn_test_box}{nn\_test\_box} representing the corners of 1196 1389 the geographical box: lonmin,lonmax,latmin,latmax 1197 \item[\np{nn\_test\_icebergs}\forcode{ = -1}] 1198 In this scheme the model reads a calving file supplied in the \np{sn\_icb} parameter. 1390 \item [{\np[=-1]{nn_test_icebergs}{nn\_test\_icebergs}}] In this scheme, the model reads a calving file supplied in the \np{sn_icb}{sn\_icb} parameter. 1199 1391 This should be a file with a field on the configuration grid (typically ORCA) 1200 1392 representing ice accumulation rate at each model point. … … 1204 1396 At each time step, a test is performed to see if there is enough ice mass to 1205 1397 calve an iceberg of each class in order (1 to 10). 1206 Note that this is the initial mass multiplied by the number each particle represents (\ie the scaling).1398 Note that this is the initial mass multiplied by the number each particle represents (\ie\ the scaling). 1207 1399 If there is enough ice, a new iceberg is spawned and the total available ice reduced accordingly. 1208 1400 \end{description} … … 1211 1403 The latter act to disintegrate the iceberg. 1212 1404 This is either all melted freshwater, 1213 or (if \np{rn \_bits\_erosion\_fraction}~$>$~0) into melt and additionally small ice bits1405 or (if \np{rn_bits_erosion_fraction}{rn\_bits\_erosion\_fraction}~$>$~0) into melt and additionally small ice bits 1214 1406 which are assumed to propagate with their larger parent and thus delay fluxing into the ocean. 1215 Melt water (and other variables on the configuration grid) are written into the main NEMOmodel output files.1407 Melt water (and other variables on the configuration grid) are written into the main \NEMO\ model output files. 1216 1408 1217 1409 Extensive diagnostics can be produced. 1218 1410 Separate output files are maintained for human-readable iceberg information. 1219 A separate file is produced for each processor (independent of \np{ln \_ctl}).1411 A separate file is produced for each processor (independent of \np{ln_ctl}{ln\_ctl}). 1220 1412 The amount of information is controlled by two integer parameters: 1221 1413 \begin{description} 1222 \item [\np{nn\_verbose\_level}] takes a value between one and four and1414 \item [{\np{nn_verbose_level}{nn\_verbose\_level}}] takes a value between one and four and 1223 1415 represents an increasing number of points in the code at which variables are written, 1224 1416 and an increasing level of obscurity. 1225 \item [\np{nn\_verbose\_write}] is the number of timesteps between writes1417 \item [{\np{nn_verbose_write}{nn\_verbose\_write}}] is the number of timesteps between writes 1226 1418 \end{description} 1227 1419 1228 Iceberg trajectories can also be written out and this is enabled by setting \np{nn \_sample\_rate}~$>$~0.1420 Iceberg trajectories can also be written out and this is enabled by setting \np{nn_sample_rate}{nn\_sample\_rate}~$>$~0. 1229 1421 A non-zero value represents how many timesteps between writes of information into the output file. 1230 1422 These output files are in NETCDF format. … … 1234 1426 since its trajectory data may be spread across multiple files. 1235 1427 1236 % ------------------------------------------------------------------------------------------------------------- 1237 % Interactions with waves (sbcwave.F90, ln_wave) 1238 % ------------------------------------------------------------------------------------------------------------- 1239 \section[Interactions with waves (\textit{sbcwave.F90}, \texttt{ln\_wave})] 1240 {Interactions with waves (\protect\mdl{sbcwave}, \protect\np{ln\_wave})} 1428 %% ================================================================================================= 1429 \section[Interactions with waves (\textit{sbcwave.F90}, \forcode{ln_wave})]{Interactions with waves (\protect\mdl{sbcwave}, \protect\np{ln_wave}{ln\_wave})} 1241 1430 \label{sec:SBC_wave} 1242 %------------------------------------------namsbc_wave-------------------------------------------------------- 1243 1244 \nlst{namsbc_wave} 1245 %------------------------------------------------------------------------------------------------------------- 1246 1247 Ocean waves represent the interface between the ocean and the atmosphere, so NEMO is extended to incorporate 1248 physical processes related to ocean surface waves, namely the surface stress modified by growth and 1249 dissipation of the oceanic wave field, the Stokes-Coriolis force and the Stokes drift impact on mass and 1250 tracer advection; moreover the neutral surface drag coefficient from a wave model can be used to evaluate 1431 1432 \begin{listing} 1433 \nlst{namsbc_wave} 1434 \caption{\forcode{&namsbc_wave}} 1435 \label{lst:namsbc_wave} 1436 \end{listing} 1437 1438 Ocean waves represent the interface between the ocean and the atmosphere, so \NEMO\ is extended to incorporate 1439 physical processes related to ocean surface waves, namely the surface stress modified by growth and 1440 dissipation of the oceanic wave field, the Stokes-Coriolis force and the Stokes drift impact on mass and 1441 tracer advection; moreover the neutral surface drag coefficient from a wave model can be used to evaluate 1251 1442 the wind stress. 1252 1443 1253 Physical processes related to ocean surface waves can be accounted by setting the logical variable 1254 \np {ln\_wave}\forcode{= .true.} in \ngn{namsbc} namelist. In addition, specific flags accounting for1255 different p orcesses should be activated as explained in the following sections.1444 Physical processes related to ocean surface waves can be accounted by setting the logical variable 1445 \np[=.true.]{ln_wave}{ln\_wave} in \nam{sbc}{sbc} namelist. In addition, specific flags accounting for 1446 different processes should be activated as explained in the following sections. 1256 1447 1257 1448 Wave fields can be provided either in forced or coupled mode: 1258 1449 \begin{description} 1259 \item [forced mode]: wave fields should be defined through the \ngn{namsbc\_wave} namelist1260 for external data names, locations, frequency, interpolation and all the miscellanous options allowed by 1261 Input Data generic Interface (see \autoref{sec:SBC_input}). 1262 \item [coupled mode]: NEMO and an external wave model can be coupled by setting \np{ln\_cpl} \forcode{= .true.}1263 in \n gn{namsbc} namelist and filling the \ngn{namsbc\_cpl} namelist.1450 \item [forced mode]: wave fields should be defined through the \nam{sbc_wave}{sbc\_wave} namelist 1451 for external data names, locations, frequency, interpolation and all the miscellanous options allowed by 1452 Input Data generic Interface (see \autoref{sec:SBC_input}). 1453 \item [coupled mode]: \NEMO\ and an external wave model can be coupled by setting \np[=.true.]{ln_cpl}{ln\_cpl} 1454 in \nam{sbc}{sbc} namelist and filling the \nam{sbc_cpl}{sbc\_cpl} namelist. 1264 1455 \end{description} 1265 1456 1266 1267 % ================================================================ 1268 % Neutral drag coefficient from wave model (ln_cdgw) 1269 1270 % ================================================================ 1271 \subsection[Neutral drag coefficient from wave model (\texttt{ln\_cdgw})] 1272 {Neutral drag coefficient from wave model (\protect\np{ln\_cdgw})} 1457 %% ================================================================================================= 1458 \subsection[Neutral drag coefficient from wave model (\forcode{ln_cdgw})]{Neutral drag coefficient from wave model (\protect\np{ln_cdgw}{ln\_cdgw})} 1273 1459 \label{subsec:SBC_wave_cdgw} 1274 1460 1275 The neutral surface drag coefficient provided from an external data source (\ie a wave model), 1276 can be used by setting the logical variable \np{ln\_cdgw} \forcode{= .true.} in \ngn{namsbc} namelist. 1277 Then using the routine \rou{turb\_ncar} and starting from the neutral drag coefficent provided, 1278 the drag coefficient is computed according to the stable/unstable conditions of the 1279 air-sea interface following \citet{large.yeager_rpt04}. 1280 1281 1282 % ================================================================ 1283 % 3D Stokes Drift (ln_sdw, nn_sdrift) 1284 % ================================================================ 1285 \subsection[3D Stokes Drift (\texttt{ln\_sdw}, \texttt{nn\_sdrift})] 1286 {3D Stokes Drift (\protect\np{ln\_sdw, nn\_sdrift})} 1461 The neutral surface drag coefficient provided from an external data source (\ie\ a wave model), 1462 can be used by setting the logical variable \np[=.true.]{ln_cdgw}{ln\_cdgw} in \nam{sbc}{sbc} namelist. 1463 Then using the routine \rou{sbcblk\_algo\_ncar} and starting from the neutral drag coefficent provided, 1464 the drag coefficient is computed according to the stable/unstable conditions of the 1465 air-sea interface following \citet{large.yeager_rpt04}. 1466 1467 %% ================================================================================================= 1468 \subsection[3D Stokes Drift (\forcode{ln_sdw} \& \forcode{nn_sdrift})]{3D Stokes Drift (\protect\np{ln_sdw}{ln\_sdw} \& \np{nn_sdrift}{nn\_sdrift})} 1287 1469 \label{subsec:SBC_wave_sdw} 1288 1470 1289 The Stokes drift is a wave driven mechanism of mass and momentum transport \citep{stokes_ibk09}. 1290 It is defined as the difference between the average velocity of a fluid parcel (Lagrangian velocity) 1291 and the current measured at a fixed point (Eulerian velocity). 1292 As waves travel, the water particles that make up the waves travel in orbital motions but 1293 without a closed path. Their movement is enhanced at the top of the orbit and slowed slightly 1294 at the bottom so the result is a net forward motion of water particles, referred to as the Stokes drift.1295 An accurate evaluation of the Stokes drift and the inclusion of related processes may lead to improved 1296 representation of surface physics in ocean general circulation models. 1297 The Stokes drift velocity $\mathbf{U}_{st}$ in deep water can be computed from the wave spectrum and may be written as: 1471 The Stokes drift is a wave driven mechanism of mass and momentum transport \citep{stokes_ibk09}. 1472 It is defined as the difference between the average velocity of a fluid parcel (Lagrangian velocity) 1473 and the current measured at a fixed point (Eulerian velocity). 1474 As waves travel, the water particles that make up the waves travel in orbital motions but 1475 without a closed path. Their movement is enhanced at the top of the orbit and slowed slightly 1476 at the bottom, so the result is a net forward motion of water particles, referred to as the Stokes drift. 1477 An accurate evaluation of the Stokes drift and the inclusion of related processes may lead to improved 1478 representation of surface physics in ocean general circulation models. %GS: reference needed 1479 The Stokes drift velocity $\mathbf{U}_{st}$ in deep water can be computed from the wave spectrum and may be written as: 1298 1480 1299 1481 \[ 1300 % \label{eq: sbc_wave_sdw}1482 % \label{eq:SBC_wave_sdw} 1301 1483 \mathbf{U}_{st} = \frac{16{\pi^3}} {g} 1302 1484 \int_0^\infty \int_{-\pi}^{\pi} (cos{\theta},sin{\theta}) {f^3} … … 1304 1486 \] 1305 1487 1306 where: ${\theta}$ is the wave direction, $f$ is the wave intrinsic frequency, 1307 $\mathrm{S}($f$,\theta)$ is the 2D frequency-direction spectrum, 1308 $k$ is the mean wavenumber defined as: 1488 where: ${\theta}$ is the wave direction, $f$ is the wave intrinsic frequency, 1489 $\mathrm{S}($f$,\theta)$ is the 2D frequency-direction spectrum, 1490 $k$ is the mean wavenumber defined as: 1309 1491 $k=\frac{2\pi}{\lambda}$ (being $\lambda$ the wavelength). \\ 1310 1492 1311 In order to evaluate the Stokes drift in a realistic ocean wave field the wave spectral shape is required1312 and its computation quickly becomes expensive as the 2D spectrum must be integrated for each vertical level. 1493 In order to evaluate the Stokes drift in a realistic ocean wave field, the wave spectral shape is required 1494 and its computation quickly becomes expensive as the 2D spectrum must be integrated for each vertical level. 1313 1495 To simplify, it is customary to use approximations to the full Stokes profile. 1314 Three possible parameterizations for the calculation for the approximate Stokes drift velocity profile 1315 are included in the code through the \np{nn \_sdrift} parameter once provided the surface Stokes drift1316 $\mathbf{U}_{st |_{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra 1317 and makes possible the estimation of the surface Stokes drift for random directional waves in 1496 Three possible parameterizations for the calculation for the approximate Stokes drift velocity profile 1497 are included in the code through the \np{nn_sdrift}{nn\_sdrift} parameter once provided the surface Stokes drift 1498 $\mathbf{U}_{st |_{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra 1499 and makes possible the estimation of the surface Stokes drift for random directional waves in 1318 1500 realistic wave conditions: 1319 1501 1320 1502 \begin{description} 1321 \item [\np{nn\_sdrift} = 0]: exponential integral profile parameterization proposed by1503 \item [{\np{nn_sdrift}{nn\_sdrift} = 0}]: exponential integral profile parameterization proposed by 1322 1504 \citet{breivik.janssen.ea_JPO14}: 1323 1505 1324 1506 \[ 1325 % \label{eq: sbc_wave_sdw_0a}1326 \mathbf{U}_{st} \cong \mathbf{U}_{st |_{z=0}} \frac{\mathrm{e}^{-2k_ez}} {1-8k_ez} 1507 % \label{eq:SBC_wave_sdw_0a} 1508 \mathbf{U}_{st} \cong \mathbf{U}_{st |_{z=0}} \frac{\mathrm{e}^{-2k_ez}} {1-8k_ez} 1327 1509 \] 1328 1510 … … 1330 1512 1331 1513 \[ 1332 % \label{eq: sbc_wave_sdw_0b}1514 % \label{eq:SBC_wave_sdw_0b} 1333 1515 k_e = \frac{|\mathbf{U}_{\left.st\right|_{z=0}}|} {|T_{st}|} 1334 1516 \quad \text{and }\ 1335 T_{st} = \frac{1}{16} \bar{\omega} H_s^2 1517 T_{st} = \frac{1}{16} \bar{\omega} H_s^2 1336 1518 \] 1337 1519 1338 1520 where $H_s$ is the significant wave height and $\omega$ is the wave frequency. 1339 1521 1340 \item [\np{nn\_sdrift} = 1]: velocity profile based on the Phillips spectrum which is considered to be a1341 reasonable estimate of the part of the spectrum most contributing to the Stokes drift velocity near the surface1522 \item [{\np{nn_sdrift}{nn\_sdrift} = 1}]: velocity profile based on the Phillips spectrum which is considered to be a 1523 reasonable estimate of the part of the spectrum mostly contributing to the Stokes drift velocity near the surface 1342 1524 \citep{breivik.bidlot.ea_OM16}: 1343 1525 1344 1526 \[ 1345 % \label{eq: sbc_wave_sdw_1}1527 % \label{eq:SBC_wave_sdw_1} 1346 1528 \mathbf{U}_{st} \cong \mathbf{U}_{st |_{z=0}} \Big[exp(2k_pz)-\beta \sqrt{-2 \pi k_pz} 1347 1529 \textit{ erf } \Big(\sqrt{-2 k_pz}\Big)\Big] … … 1350 1532 where $erf$ is the complementary error function and $k_p$ is the peak wavenumber. 1351 1533 1352 \item [\np{nn\_sdrift} = 2]: velocity profile based on the Phillips spectrum as for \np{nn\_sdrift} = 11534 \item [{\np{nn_sdrift}{nn\_sdrift} = 2}]: velocity profile based on the Phillips spectrum as for \np{nn_sdrift}{nn\_sdrift} = 1 1353 1535 but using the wave frequency from a wave model. 1354 1536 1355 1537 \end{description} 1356 1538 1357 The Stokes drift enters the wave-averaged momentum equation, as well as the tracer advection equations 1358 and its effect on the evolution of the sea-surface height ${\eta}$ is considered as follows: 1539 The Stokes drift enters the wave-averaged momentum equation, as well as the tracer advection equations 1540 and its effect on the evolution of the sea-surface height ${\eta}$ is considered as follows: 1359 1541 1360 1542 \[ 1361 % \label{eq: sbc_wave_eta_sdw}1543 % \label{eq:SBC_wave_eta_sdw} 1362 1544 \frac{\partial{\eta}}{\partial{t}} = 1363 1545 -\nabla_h \int_{-H}^{\eta} (\mathbf{U} + \mathbf{U}_{st}) dz 1364 1546 \] 1365 1547 1366 The tracer advection equation is also modified in order for Eulerian ocean models to properly account 1367 for unresolved wave effect. The divergence of the wave tracer flux equals the mean tracer advection 1368 that is induced by the three-dimensional Stokes velocity. 1369 The advective equation for a tracer $c$ combining the effects of the mean current and sea surface waves 1370 can be formulated as follows: 1548 The tracer advection equation is also modified in order for Eulerian ocean models to properly account 1549 for unresolved wave effect. The divergence of the wave tracer flux equals the mean tracer advection 1550 that is induced by the three-dimensional Stokes velocity. 1551 The advective equation for a tracer $c$ combining the effects of the mean current and sea surface waves 1552 can be formulated as follows: 1371 1553 1372 1554 \[ 1373 % \label{eq: sbc_wave_tra_sdw}1555 % \label{eq:SBC_wave_tra_sdw} 1374 1556 \frac{\partial{c}}{\partial{t}} = 1375 1557 - (\mathbf{U} + \mathbf{U}_{st}) \cdot \nabla{c} 1376 1558 \] 1377 1559 1378 1379 % ================================================================ 1380 % Stokes-Coriolis term (ln_stcor) 1381 % ================================================================ 1382 \subsection[Stokes-Coriolis term (\texttt{ln\_stcor})] 1383 {Stokes-Coriolis term (\protect\np{ln\_stcor})} 1560 %% ================================================================================================= 1561 \subsection[Stokes-Coriolis term (\forcode{ln_stcor})]{Stokes-Coriolis term (\protect\np{ln_stcor}{ln\_stcor})} 1384 1562 \label{subsec:SBC_wave_stcor} 1385 1563 1386 In a rotating ocean, waves exert a wave-induced stress on the mean ocean circulation which results 1387 in a force equal to $\mathbf{U}_{st}$×$f$, where $f$ is the Coriolis parameter. 1388 This additional force may have impact on the Ekman turning of the surface current. 1389 In order to include this term, once evaluated the Stokes drift (using one of the 3 possible 1390 approximations described in \autoref{subsec:SBC_wave_sdw}), 1391 \np{ln\_stcor}\forcode{ = .true.} has to be set. 1392 1393 1394 % ================================================================ 1395 % Waves modified stress (ln_tauwoc, ln_tauw) 1396 % ================================================================ 1397 \subsection[Wave modified sress (\texttt{ln\_tauwoc}, \texttt{ln\_tauw})] 1398 {Wave modified sress (\protect\np{ln\_tauwoc, ln\_tauw})} 1564 In a rotating ocean, waves exert a wave-induced stress on the mean ocean circulation which results 1565 in a force equal to $\mathbf{U}_{st}$×$f$, where $f$ is the Coriolis parameter. 1566 This additional force may have impact on the Ekman turning of the surface current. 1567 In order to include this term, once evaluated the Stokes drift (using one of the 3 possible 1568 approximations described in \autoref{subsec:SBC_wave_sdw}), 1569 \np[=.true.]{ln_stcor}{ln\_stcor} has to be set. 1570 1571 %% ================================================================================================= 1572 \subsection[Wave modified stress (\forcode{ln_tauwoc} \& \forcode{ln_tauw})]{Wave modified sress (\protect\np{ln_tauwoc}{ln\_tauwoc} \& \np{ln_tauw}{ln\_tauw})} 1399 1573 \label{subsec:SBC_wave_tauw} 1400 1574 1401 The surface stress felt by the ocean is the atmospheric stress minus the net stress going 1402 into the waves \citep{janssen.breivik.ea_rpt13}. Therefore, when waves are growing, momentum and energy is spent and is not 1403 available for forcing the mean circulation, while in the opposite case of a decaying sea 1404 state more momentum is available for forcing the ocean.1405 Only when the sea state is in equilibrium the ocean is forced by the atmospheric stress,1406 but in practice an equilibrium sea state is a fairly rare event.1407 So the atmospheric stress felt by the ocean circulation $\tau_{oc,a}$ can be expressed as: 1575 The surface stress felt by the ocean is the atmospheric stress minus the net stress going 1576 into the waves \citep{janssen.breivik.ea_rpt13}. Therefore, when waves are growing, momentum and energy is spent and is not 1577 available for forcing the mean circulation, while in the opposite case of a decaying sea 1578 state, more momentum is available for forcing the ocean. 1579 Only when the sea state is in equilibrium, the ocean is forced by the atmospheric stress, 1580 but in practice, an equilibrium sea state is a fairly rare event. 1581 So the atmospheric stress felt by the ocean circulation $\tau_{oc,a}$ can be expressed as: 1408 1582 1409 1583 \[ 1410 % \label{eq: sbc_wave_tauoc}1584 % \label{eq:SBC_wave_tauoc} 1411 1585 \tau_{oc,a} = \tau_a - \tau_w 1412 1586 \] … … 1416 1590 1417 1591 \[ 1418 % \label{eq: sbc_wave_tauw}1592 % \label{eq:SBC_wave_tauw} 1419 1593 \tau_w = \rho g \int {\frac{dk}{c_p} (S_{in}+S_{nl}+S_{diss})} 1420 1594 \] 1421 1595 1422 1596 where: $c_p$ is the phase speed of the gravity waves, 1423 $S_{in}$, $S_{nl}$ and $S_{diss}$ are three source terms that represent 1424 the physics of ocean waves. The first one, $S_{in}$, describes the generation 1425 of ocean waves by wind and therefore represents the momentum and energy transfer 1426 from air to ocean waves; the second term $S_{nl}$ denotes 1427 the nonlinear transfer by resonant four-wave interactions; while the third term $S_{diss}$ 1428 describes the dissipation of waves by processes such as white-capping, large scale breaking 1597 $S_{in}$, $S_{nl}$ and $S_{diss}$ are three source terms that represent 1598 the physics of ocean waves. The first one, $S_{in}$, describes the generation 1599 of ocean waves by wind and therefore represents the momentum and energy transfer 1600 from air to ocean waves; the second term $S_{nl}$ denotes 1601 the nonlinear transfer by resonant four-wave interactions; while the third term $S_{diss}$ 1602 describes the dissipation of waves by processes such as white-capping, large scale breaking 1429 1603 eddy-induced damping. 1430 1604 1431 The wave stress derived from an external wave model can be provided either through the normalized 1432 wave stress into the ocean by setting \np{ln\_tauwoc}\forcode{ = .true.}, or through the zonal and 1433 meridional stress components by setting \np{ln\_tauw}\forcode{ = .true.}. 1434 1435 1436 % ================================================================ 1437 % Miscellanea options 1438 % ================================================================ 1605 The wave stress derived from an external wave model can be provided either through the normalized 1606 wave stress into the ocean by setting \np[=.true.]{ln_tauwoc}{ln\_tauwoc}, or through the zonal and 1607 meridional stress components by setting \np[=.true.]{ln_tauw}{ln\_tauw}. 1608 1609 %% ================================================================================================= 1439 1610 \section{Miscellaneous options} 1440 1611 \label{sec:SBC_misc} 1441 1612 1442 % ------------------------------------------------------------------------------------------------------------- 1443 % Diurnal cycle 1444 % ------------------------------------------------------------------------------------------------------------- 1445 \subsection[Diurnal cycle (\textit{sbcdcy.F90})] 1446 {Diurnal cycle (\protect\mdl{sbcdcy})} 1613 %% ================================================================================================= 1614 \subsection[Diurnal cycle (\textit{sbcdcy.F90})]{Diurnal cycle (\protect\mdl{sbcdcy})} 1447 1615 \label{subsec:SBC_dcy} 1448 %------------------------------------------namsbc_rnf---------------------------------------------------- 1449 % 1450 \nlst{namsbc} 1451 %------------------------------------------------------------------------------------------------------------- 1452 1453 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1616 1454 1617 \begin{figure}[!t] 1455 \begin{center} 1456 \includegraphics[width=\textwidth]{Fig_SBC_diurnal} 1457 \caption{ 1458 \protect\label{fig:SBC_diurnal} 1459 Example of recontruction of the diurnal cycle variation of short wave flux from daily mean values. 1460 The reconstructed diurnal cycle (black line) is chosen as 1461 the mean value of the analytical cycle (blue line) over a time step, 1462 not as the mid time step value of the analytically cycle (red square). 1463 From \citet{bernie.guilyardi.ea_CD07}. 1464 } 1465 \end{center} 1618 \centering 1619 \includegraphics[width=0.66\textwidth]{SBC_diurnal} 1620 \caption[Reconstruction of the diurnal cycle variation of short wave flux]{ 1621 Example of reconstruction of the diurnal cycle variation of short wave flux from 1622 daily mean values. 1623 The reconstructed diurnal cycle (black line) is chosen as 1624 the mean value of the analytical cycle (blue line) over a time step, 1625 not as the mid time step value of the analytically cycle (red square). 1626 From \citet{bernie.guilyardi.ea_CD07}.} 1627 \label{fig:SBC_diurnal} 1466 1628 \end{figure} 1467 %>>>>>>>>>>>>>>>>>>>>>>>>>>>>1468 1629 1469 1630 \cite{bernie.woolnough.ea_JC05} have shown that to capture 90$\%$ of the diurnal variability of SST requires a vertical resolution in upper ocean of 1~m or better and a temporal resolution of the surface fluxes of 3~h or less. 1470 Unfortunately high frequency forcing fields are rare, not to say inexistent. 1471 Nevertheless, it is possible to obtain a reasonable diurnal cycle of the SST knowning only short wave flux (SWF) at 1472 high frequency \citep{bernie.guilyardi.ea_CD07}. 1631 %Unfortunately high frequency forcing fields are rare, not to say inexistent. GS: not true anymore ! 1632 Nevertheless, it is possible to obtain a reasonable diurnal cycle of the SST knowning only short wave flux (SWF) at high frequency \citep{bernie.guilyardi.ea_CD07}. 1473 1633 Furthermore, only the knowledge of daily mean value of SWF is needed, 1474 1634 as higher frequency variations can be reconstructed from them, 1475 1635 assuming that the diurnal cycle of SWF is a scaling of the top of the atmosphere diurnal cycle of incident SWF. 1476 The \cite{bernie.guilyardi.ea_CD07} reconstruction algorithm is available in \NEMO by1477 setting \np {ln\_dm2dc}\forcode{ = .true.} (a \textit{\ngn{namsbc}} namelist variable) when1478 using CORE bulk formulea (\np{ln\_blk\_core}\forcode{ = .true.}) or1479 the flux formulation (\np {ln\_flx}\forcode{ = .true.}).1636 The \cite{bernie.guilyardi.ea_CD07} reconstruction algorithm is available in \NEMO\ by 1637 setting \np[=.true.]{ln_dm2dc}{ln\_dm2dc} (a \textit{\nam{sbc}{sbc}} namelist variable) when 1638 using a bulk formulation (\np[=.true.]{ln_blk}{ln\_blk}) or 1639 the flux formulation (\np[=.true.]{ln_flx}{ln\_flx}). 1480 1640 The reconstruction is performed in the \mdl{sbcdcy} module. 1481 1641 The detail of the algoritm used can be found in the appendix~A of \cite{bernie.guilyardi.ea_CD07}. 1482 The algorithm preserve the daily mean incoming SWF as the reconstructed SWF at1642 The algorithm preserves the daily mean incoming SWF as the reconstructed SWF at 1483 1643 a given time step is the mean value of the analytical cycle over this time step (\autoref{fig:SBC_diurnal}). 1484 1644 The use of diurnal cycle reconstruction requires the input SWF to be daily 1485 (\ie a frequency of 24 and a time interpolation set to true in \np{sn\_qsr} namelist parameter).1486 Furthermore, it is recommended to have a least 8 surface module time step per day,1645 (\ie\ a frequency of 24 hours and a time interpolation set to true in \np{sn_qsr}{sn\_qsr} namelist parameter). 1646 Furthermore, it is recommended to have a least 8 surface module time steps per day, 1487 1647 that is $\rdt \ nn\_fsbc < 10,800~s = 3~h$. 1488 1648 An example of recontructed SWF is given in \autoref{fig:SBC_dcy} for a 12 reconstructed diurnal cycle, 1489 1649 one every 2~hours (from 1am to 11pm). 1490 1650 1491 %>>>>>>>>>>>>>>>>>>>>>>>>>>>>1492 1651 \begin{figure}[!t] 1493 \begin{center} 1494 \includegraphics[width=\textwidth]{Fig_SBC_dcy} 1495 \caption{ 1496 \protect\label{fig:SBC_dcy} 1497 Example of recontruction of the diurnal cycle variation of short wave flux from 1498 daily mean values on an ORCA2 grid with a time sampling of 2~hours (from 1am to 11pm). 1499 The display is on (i,j) plane. 1500 } 1501 \end{center} 1652 \centering 1653 \includegraphics[width=0.66\textwidth]{SBC_dcy} 1654 \caption[Reconstruction of the diurnal cycle variation of short wave flux on an ORCA2 grid]{ 1655 Example of reconstruction of the diurnal cycle variation of short wave flux from 1656 daily mean values on an ORCA2 grid with a time sampling of 2~hours (from 1am to 11pm). 1657 The display is on (i,j) plane.} 1658 \label{fig:SBC_dcy} 1502 1659 \end{figure} 1503 %>>>>>>>>>>>>>>>>>>>>>>>>>>>>1504 1660 1505 1661 Note also that the setting a diurnal cycle in SWF is highly recommended when … … 1507 1663 an inconsistency between the scale of the vertical resolution and the forcing acting on that scale. 1508 1664 1509 % ------------------------------------------------------------------------------------------------------------- 1510 % Rotation of vector pairs onto the model grid directions 1511 % ------------------------------------------------------------------------------------------------------------- 1665 %% ================================================================================================= 1512 1666 \subsection{Rotation of vector pairs onto the model grid directions} 1513 1667 \label{subsec:SBC_rotation} 1514 1668 1515 When using a flux (\np{ln\_flx}\forcode{ = .true.}) or 1516 bulk (\np{ln\_clio}\forcode{ = .true.} or \np{ln\_core}\forcode{ = .true.}) formulation, 1669 When using a flux (\np[=.true.]{ln_flx}{ln\_flx}) or bulk (\np[=.true.]{ln_blk}{ln\_blk}) formulation, 1517 1670 pairs of vector components can be rotated from east-north directions onto the local grid directions. 1518 1671 This is particularly useful when interpolation on the fly is used since here any vectors are likely to 1519 1672 be defined relative to a rectilinear grid. 1520 To activate this option a non-empty string is supplied in the rotation pair column of the relevant namelist.1521 The eastward component must start with "U" and the northward component with "V". 1673 To activate this option, a non-empty string is supplied in the rotation pair column of the relevant namelist. 1674 The eastward component must start with "U" and the northward component with "V". 1522 1675 The remaining characters in the strings are used to identify which pair of components go together. 1523 1676 So for example, strings "U1" and "V1" next to "utau" and "vtau" would pair the wind stress components together and … … 1527 1680 The rot\_rep routine from the \mdl{geo2ocean} module is used to perform the rotation. 1528 1681 1529 % ------------------------------------------------------------------------------------------------------------- 1530 % Surface restoring to observed SST and/or SSS 1531 % ------------------------------------------------------------------------------------------------------------- 1532 \subsection[Surface restoring to observed SST and/or SSS (\textit{sbcssr.F90})] 1533 {Surface restoring to observed SST and/or SSS (\protect\mdl{sbcssr})} 1682 %% ================================================================================================= 1683 \subsection[Surface restoring to observed SST and/or SSS (\textit{sbcssr.F90})]{Surface restoring to observed SST and/or SSS (\protect\mdl{sbcssr})} 1534 1684 \label{subsec:SBC_ssr} 1535 %------------------------------------------namsbc_ssr---------------------------------------------------- 1536 1537 \nlst{namsbc_ssr} 1538 %------------------------------------------------------------------------------------------------------------- 1539 1540 IOptions are defined through the \ngn{namsbc\_ssr} namelist variables. 1541 On forced mode using a flux formulation (\np{ln\_flx}\forcode{ = .true.}), 1685 1686 \begin{listing} 1687 \nlst{namsbc_ssr} 1688 \caption{\forcode{&namsbc_ssr}} 1689 \label{lst:namsbc_ssr} 1690 \end{listing} 1691 1692 Options are defined through the \nam{sbc_ssr}{sbc\_ssr} namelist variables. 1693 On forced mode using a flux formulation (\np[=.true.]{ln_flx}{ln\_flx}), 1542 1694 a feedback term \emph{must} be added to the surface heat flux $Q_{ns}^o$: 1543 1695 \[ 1544 % \label{eq: sbc_dmp_q}1696 % \label{eq:SBC_dmp_q} 1545 1697 Q_{ns} = Q_{ns}^o + \frac{dQ}{dT} \left( \left. T \right|_{k=1} - SST_{Obs} \right) 1546 1698 \] … … 1548 1700 $T$ is the model surface layer temperature and 1549 1701 $\frac{dQ}{dT}$ is a negative feedback coefficient usually taken equal to $-40~W/m^2/K$. 1550 For a $50~m$ mixed-layer depth, this value corresponds to a relaxation time scale of two months. 1551 This term ensures that if $T$ perfectly matches the supplied SST, then $Q$ is equal to $Q_o$. 1702 For a $50~m$ mixed-layer depth, this value corresponds to a relaxation time scale of two months. 1703 This term ensures that if $T$ perfectly matches the supplied SST, then $Q$ is equal to $Q_o$. 1552 1704 1553 1705 In the fresh water budget, a feedback term can also be added. … … 1555 1707 1556 1708 \begin{equation} 1557 \label{eq: sbc_dmp_emp}1709 \label{eq:SBC_dmp_emp} 1558 1710 \textit{emp} = \textit{emp}_o + \gamma_s^{-1} e_{3t} \frac{ \left(\left.S\right|_{k=1}-SSS_{Obs}\right)} 1559 1711 {\left.S\right|_{k=1}} … … 1566 1718 $\left.S\right|_{k=1}$ is the model surface layer salinity and 1567 1719 $\gamma_s$ is a negative feedback coefficient which is provided as a namelist parameter. 1568 Unlike heat flux, there is no physical justification for the feedback term in \autoref{eq: sbc_dmp_emp} as1720 Unlike heat flux, there is no physical justification for the feedback term in \autoref{eq:SBC_dmp_emp} as 1569 1721 the atmosphere does not care about ocean surface salinity \citep{madec.delecluse_IWN97}. 1570 1722 The SSS restoring term should be viewed as a flux correction on freshwater fluxes to 1571 1723 reduce the uncertainties we have on the observed freshwater budget. 1572 1724 1573 % ------------------------------------------------------------------------------------------------------------- 1574 % Handling of ice-covered area 1575 % ------------------------------------------------------------------------------------------------------------- 1725 %% ================================================================================================= 1576 1726 \subsection{Handling of ice-covered area (\textit{sbcice\_...})} 1577 1727 \label{subsec:SBC_ice-cover} … … 1579 1729 The presence at the sea surface of an ice covered area modifies all the fluxes transmitted to the ocean. 1580 1730 There are several way to handle sea-ice in the system depending on 1581 the value of the \np{nn \_ice} namelist parameter found in \ngn{namsbc} namelist.1731 the value of the \np{nn_ice}{nn\_ice} namelist parameter found in \nam{sbc}{sbc} namelist. 1582 1732 \begin{description} 1583 \item[nn{\_}ice = 0] 1584 there will never be sea-ice in the computational domain. 1733 \item [nn\_ice = 0] there will never be sea-ice in the computational domain. 1585 1734 This is a typical namelist value used for tropical ocean domain. 1586 1735 The surface fluxes are simply specified for an ice-free ocean. 1587 1736 No specific things is done for sea-ice. 1588 \item[nn{\_}ice = 1] 1589 sea-ice can exist in the computational domain, but no sea-ice model is used. 1737 \item [nn\_ice = 1] sea-ice can exist in the computational domain, but no sea-ice model is used. 1590 1738 An observed ice covered area is read in a file. 1591 1739 Below this area, the SST is restored to the freezing point and … … 1595 1743 This prevents deep convection to occur when trying to reach the freezing point 1596 1744 (and so ice covered area condition) while the SSS is too large. 1597 This manner of managing sea-ice area, just by using siIF case,1745 This manner of managing sea-ice area, just by using a IF case, 1598 1746 is usually referred as the \textit{ice-if} model. 1599 It can be found in the \mdl{sbcice{\_}if} module. 1600 \item[nn{\_}ice = 2 or more] 1601 A full sea ice model is used. 1747 It can be found in the \mdl{sbcice\_if} module. 1748 \item [nn\_ice = 2 or more] A full sea ice model is used. 1602 1749 This model computes the ice-ocean fluxes, 1603 1750 that are combined with the air-sea fluxes using the ice fraction of each model cell to 1604 provide the surface ocean fluxes.1605 Note that the activation of a sea-ice model is is done by defining a CPP key (\key{lim3} or \key{cice}).1606 The activation automatically overwrites the read value of nn {\_}ice to its appropriate value1607 (\ie $2$ for LIM-3 or $3$ for CICE).1751 provide the surface averaged ocean fluxes. 1752 Note that the activation of a sea-ice model is done by defining a CPP key (\key{si3} or \key{cice}). 1753 The activation automatically overwrites the read value of nn\_ice to its appropriate value 1754 (\ie\ $2$ for SI3 or $3$ for CICE). 1608 1755 \end{description} 1609 1756 1610 1757 % {Description of Ice-ocean interface to be added here or in LIM 2 and 3 doc ?} 1611 1612 \subsection[Interface to CICE (\textit{sbcice\_cice.F90})] 1613 {Interface to CICE (\protect\mdl{sbcice\_cice})} 1758 %GS: ocean-ice (SI3) interface is not located in SBC directory anymore, so it should be included in SI3 doc 1759 1760 %% ================================================================================================= 1761 \subsection[Interface to CICE (\textit{sbcice\_cice.F90})]{Interface to CICE (\protect\mdl{sbcice\_cice})} 1614 1762 \label{subsec:SBC_cice} 1615 1763 1616 It is now possible to couple a regional or global NEMOconfiguration (without AGRIF)1764 It is possible to couple a regional or global \NEMO\ configuration (without AGRIF) 1617 1765 to the CICE sea-ice model by using \key{cice}. 1618 1766 The CICE code can be obtained from \href{http://oceans11.lanl.gov/trac/CICE/}{LANL} and 1619 1767 the additional 'hadgem3' drivers will be required, even with the latest code release. 1620 Input grid files consistent with those used in NEMOwill also be needed,1768 Input grid files consistent with those used in \NEMO\ will also be needed, 1621 1769 and CICE CPP keys \textbf{ORCA\_GRID}, \textbf{CICE\_IN\_NEMO} and \textbf{coupled} should be used 1622 1770 (seek advice from UKMO if necessary). 1623 Currently the code is only designed to work when using the CORE forcing option for NEMO1624 (with \textit{calc\_strair}\forcode{ = .true.} and \textit{calc\_Tsfc}\forcode{ =.true.} in the CICE name-list),1625 or alternatively when NEMOis coupled to the HadGAM3 atmosphere model1626 (with \textit{calc\_strair}\forcode{ = .false.} and \textit{calc\_Tsfc}\forcode{ =false}).1627 The code is intended to be used with \np{nn \_fsbc} set to 11771 Currently, the code is only designed to work when using the NCAR forcing option for \NEMO\ %GS: still true ? 1772 (with \textit{calc\_strair}\forcode{=.true.} and \textit{calc\_Tsfc}\forcode{=.true.} in the CICE name-list), 1773 or alternatively when \NEMO\ is coupled to the HadGAM3 atmosphere model 1774 (with \textit{calc\_strair}\forcode{=.false.} and \textit{calc\_Tsfc}\forcode{=false}). 1775 The code is intended to be used with \np{nn_fsbc}{nn\_fsbc} set to 1 1628 1776 (although coupling ocean and ice less frequently should work, 1629 1777 it is possible the calculation of some of the ocean-ice fluxes needs to be modified slightly - 1630 1778 the user should check that results are not significantly different to the standard case). 1631 1779 1632 There are two options for the technical coupling between NEMOand CICE.1780 There are two options for the technical coupling between \NEMO\ and CICE. 1633 1781 The standard version allows complete flexibility for the domain decompositions in the individual models, 1634 1782 but this is at the expense of global gather and scatter operations in the coupling which 1635 1783 become very expensive on larger numbers of processors. 1636 The alternative option (using \key{nemocice\_decomp} for both NEMOand CICE) ensures that1784 The alternative option (using \key{nemocice\_decomp} for both \NEMO\ and CICE) ensures that 1637 1785 the domain decomposition is identical in both models (provided domain parameters are set appropriately, 1638 1786 and \textit{processor\_shape~=~square-ice} and \textit{distribution\_wght~=~block} in the CICE name-list) and … … 1641 1789 there is no sea ice. 1642 1790 1643 % ------------------------------------------------------------------------------------------------------------- 1644 % Freshwater budget control 1645 % ------------------------------------------------------------------------------------------------------------- 1646 \subsection[Freshwater budget control (\textit{sbcfwb.F90})] 1647 {Freshwater budget control (\protect\mdl{sbcfwb})} 1791 %% ================================================================================================= 1792 \subsection[Freshwater budget control (\textit{sbcfwb.F90})]{Freshwater budget control (\protect\mdl{sbcfwb})} 1648 1793 \label{subsec:SBC_fwb} 1649 1794 1650 For global ocean simulation it can be useful to introduce a control of the mean sea level in order to1795 For global ocean simulation, it can be useful to introduce a control of the mean sea level in order to 1651 1796 prevent unrealistic drift of the sea surface height due to inaccuracy in the freshwater fluxes. 1652 In \NEMO, two way of controlling the the freshwater budget. 1797 In \NEMO, two way of controlling the freshwater budget are proposed: 1798 1653 1799 \begin{description} 1654 \item[\np{nn\_fwb}\forcode{ = 0}] 1655 no control at all. 1800 \item [{\np[=0]{nn_fwb}{nn\_fwb}}] no control at all. 1656 1801 The mean sea level is free to drift, and will certainly do so. 1657 \item[\np{nn\_fwb}\forcode{ = 1}] 1658 global mean \textit{emp} set to zero at each model time step. 1659 %Note that with a sea-ice model, this technique only control the mean sea level with linear free surface (\key{vvl} not defined) and no mass flux between ocean and ice (as it is implemented in the current ice-ocean coupling). 1660 \item[\np{nn\_fwb}\forcode{ = 2}] 1661 freshwater budget is adjusted from the previous year annual mean budget which 1802 \item [{\np[=1]{nn_fwb}{nn\_fwb}}] global mean \textit{emp} set to zero at each model time step. 1803 %GS: comment below still relevant ? 1804 %Note that with a sea-ice model, this technique only controls the mean sea level with linear free surface and no mass flux between ocean and ice (as it is implemented in the current ice-ocean coupling). 1805 \item [{\np[=2]{nn_fwb}{nn\_fwb}}] freshwater budget is adjusted from the previous year annual mean budget which 1662 1806 is read in the \textit{EMPave\_old.dat} file. 1663 1807 As the model uses the Boussinesq approximation, the annual mean fresh water budget is simply evaluated from 1664 the change in the mean sea level at January the first and saved in the \textit{EMPav.dat} file. 1808 the change in the mean sea level at January the first and saved in the \textit{EMPav.dat} file. 1665 1809 \end{description} 1666 1810 1667 1668 1669 1811 % Griffies doc: 1670 % When running ocean-ice simulations, we are not explicitly representing land processes, 1671 % such as rivers, catchment areas, snow accumulation, etc. However, to reduce model drift, 1672 % it is important to balance the hydrological cycle in ocean-ice models. 1673 % We thus need to prescribe some form of global normalization to the precipitation minus evaporation plus river runoff. 1674 % The result of the normalization should be a global integrated zero net water input to the ocean-ice system over 1675 % a chosen time scale. 1676 %How often the normalization is done is a matter of choice. In mom4p1, we choose to do so at each model time step, 1677 % so that there is always a zero net input of water to the ocean-ice system. 1678 % Others choose to normalize over an annual cycle, in which case the net imbalance over an annual cycle is used 1679 % to alter the subsequent year�s water budget in an attempt to damp the annual water imbalance. 1680 % Note that the annual budget approach may be inappropriate with interannually varying precipitation forcing. 1681 % When running ocean-ice coupled models, it is incorrect to include the water transport between the ocean 1682 % and ice models when aiming to balance the hydrological cycle. 1683 % The reason is that it is the sum of the water in the ocean plus ice that should be balanced when running ocean-ice models, 1684 % not the water in any one sub-component. As an extreme example to illustrate the issue, 1685 % consider an ocean-ice model with zero initial sea ice. As the ocean-ice model spins up, 1686 % there should be a net accumulation of water in the growing sea ice, and thus a net loss of water from the ocean. 1687 % The total water contained in the ocean plus ice system is constant, but there is an exchange of water between 1688 % the subcomponents. This exchange should not be part of the normalization used to balance the hydrological cycle 1689 % in ocean-ice models. 1690 1691 \biblio 1692 1693 \pindex 1812 % When running ocean-ice simulations, we are not explicitly representing land processes, 1813 % such as rivers, catchment areas, snow accumulation, etc. However, to reduce model drift, 1814 % it is important to balance the hydrological cycle in ocean-ice models. 1815 % We thus need to prescribe some form of global normalization to the precipitation minus evaporation plus river runoff. 1816 % The result of the normalization should be a global integrated zero net water input to the ocean-ice system over 1817 % a chosen time scale. 1818 % How often the normalization is done is a matter of choice. In mom4p1, we choose to do so at each model time step, 1819 % so that there is always a zero net input of water to the ocean-ice system. 1820 % Others choose to normalize over an annual cycle, in which case the net imbalance over an annual cycle is used 1821 % to alter the subsequent year�s water budget in an attempt to damp the annual water imbalance. 1822 % Note that the annual budget approach may be inappropriate with interannually varying precipitation forcing. 1823 % When running ocean-ice coupled models, it is incorrect to include the water transport between the ocean 1824 % and ice models when aiming to balance the hydrological cycle. 1825 % The reason is that it is the sum of the water in the ocean plus ice that should be balanced when running ocean-ice models, 1826 % not the water in any one sub-component. As an extreme example to illustrate the issue, 1827 % consider an ocean-ice model with zero initial sea ice. As the ocean-ice model spins up, 1828 % there should be a net accumulation of water in the growing sea ice, and thus a net loss of water from the ocean. 1829 % The total water contained in the ocean plus ice system is constant, but there is an exchange of water between 1830 % the subcomponents. This exchange should not be part of the normalization used to balance the hydrological cycle 1831 % in ocean-ice models. 1832 1833 \subinc{\input{../../global/epilogue}} 1694 1834 1695 1835 \end{document}
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