Changeset 11573 for NEMO/branches/2019/dev_r11233_AGRIF-05_jchanut_vert_coord_interp/doc/latex/NEMO/subfiles/chap_SBC.tex
- Timestamp:
- 2019-09-19T11:18:03+02:00 (5 years ago)
- File:
-
- 1 edited
Legend:
- Unmodified
- Added
- Removed
-
NEMO/branches/2019/dev_r11233_AGRIF-05_jchanut_vert_coord_interp/doc/latex/NEMO/subfiles/chap_SBC.tex
r11179 r11573 2 2 3 3 \begin{document} 4 % ================================================================ 5 % Chapter —— Surface Boundary Condition (SBC, ISF, ICB) 6 % ================================================================ 7 \chapter{Surface Boundary Condition (SBC, ISF, ICB)} 4 5 % ================================================================ 6 % Chapter —— Surface Boundary Condition (SBC, SAS, ISF, ICB) 7 % ================================================================ 8 \chapter{Surface Boundary Condition (SBC, SAS, ISF, ICB)} 8 9 \label{chap:SBC} 9 \ minitoc10 \chaptertoc 10 11 11 12 \newpage … … 13 14 %---------------------------------------namsbc-------------------------------------------------- 14 15 15 \nlst{namsbc} 16 \begin{listing} 17 \nlst{namsbc} 18 \caption{\forcode{&namsbc}} 19 \label{lst:namsbc} 20 \end{listing} 16 21 %-------------------------------------------------------------------------------------------------------------- 17 22 18 The ocean needs six fields as surface boundary condition: 23 The ocean needs seven fields as surface boundary condition: 24 19 25 \begin{itemize} 20 26 \item … … 26 32 \item 27 33 the surface salt flux associated with freezing/melting of seawater $\left( {\textit{sfx}} \right)$ 34 \item 35 the atmospheric pressure at the ocean surface $\left( p_a \right)$ 28 36 \end{itemize} 29 plus an optional field: 37 38 Four different ways are available to provide the seven fields to the ocean. They are controlled by 39 namelist \nam{sbc} variables: 40 30 41 \begin{itemize} 31 \item the atmospheric pressure at the ocean surface $\left( p_a \right)$ 42 \item 43 a bulk formulation (\np{ln\_blk}\forcode{=.true.} with four possible bulk algorithms), 44 \item 45 a flux formulation (\np{ln\_flx}\forcode{=.true.}), 46 \item 47 a coupled or mixed forced/coupled formulation (exchanges with a atmospheric model via the OASIS coupler), 48 (\np{ln\_cpl} or \np{ln\_mixcpl}\forcode{=.true.}), 49 \item 50 a user defined formulation (\np{ln\_usr}\forcode{=.true.}). 32 51 \end{itemize} 33 52 34 Four different ways to provide the first six fields to the ocean are available which are controlled by35 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) and40 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 53 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 54 55 When the fields are supplied from data files (bulk, flux and mixed formulations), 56 the input fields do not need to be supplied on the model grid. 57 Instead, a file of coordinates and weights can be supplied to map the data from the input fields grid to 49 58 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 coastsas59 If the "Interpolation on the Fly" option is used, input data belonging to land points (in the native grid) 60 should be masked or filled to avoid spurious results in proximity of the coasts, as 52 61 large sea-land gradients characterize most of the atmospheric variables. 53 62 54 63 In addition, the resulting fields can be further modified using several namelist options. 55 These options control 64 These options control: 65 56 66 \begin{itemize} 57 67 \item 58 68 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}) ; 69 the local grid directions in the model, 70 \item 71 the use of a land/sea mask for input fields (\np{nn\_lsm}\forcode{=.true.}), 72 \item 73 the addition of a surface restoring term to observed SST and/or SSS (\np{ln\_ssr}\forcode{=.true.}), 74 \item 75 the modification of fluxes below ice-covered areas (using climatological ice-cover or a sea-ice model) 76 (\np{nn\_ice}\forcode{=0..3}), 77 \item 78 the addition of river runoffs as surface freshwater fluxes or lateral inflow (\np{ln\_rnf}\forcode{=.true.}), 79 \item 80 the addition of ice-shelf melting as lateral inflow (parameterisation) or 81 as fluxes applied at the land-ice ocean interface (\np{ln\_isf}\forcode{=.true.}), 70 82 \item 71 83 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.}). 84 (\np{nn\_fwb}\forcode{=0..2}), 85 \item 86 the transformation of the solar radiation (if provided as daily mean) into an analytical diurnal cycle 87 (\np{ln\_dm2dc}\forcode{=.true.}), 88 \item 89 the activation of wave effects from an external wave model (\np{ln\_wave}\forcode{=.true.}), 90 \item 91 a neutral drag coefficient is read from an external wave model (\np{ln\_cdgw}\forcode{=.true.}), 92 \item 93 the Stokes drift from an external wave model is accounted for (\np{ln\_sdw}\forcode{=.true.}), 94 \item 95 the choice of the Stokes drift profile parameterization (\np{nn\_sdrift}\forcode{=0..2}), 96 \item 97 the surface stress given to the ocean is modified by surface waves (\np{ln\_tauwoc}\forcode{=.true.}), 98 \item 99 the surface stress given to the ocean is read from an external wave model (\np{ln\_tauw}\forcode{=.true.}), 100 \item 101 the Stokes-Coriolis term is included (\np{ln\_stcor}\forcode{=.true.}), 102 \item 103 the light penetration in the ocean (\np{ln\_traqsr}\forcode{=.true.} with namelist \nam{tra\_qsr}), 104 \item 105 the atmospheric surface pressure gradient effect on ocean and ice dynamics (\np{ln\_apr\_dyn}\forcode{=.true.} with namelist \nam{sbc\_apr}), 106 \item 107 the effect of sea-ice pressure on the ocean (\np{ln\_ice\_embd}\forcode{=.true.}). 84 108 \end{itemize} 85 109 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.110 In this chapter, we first discuss where the surface boundary conditions appear in the model equations. 111 Then we present the three ways of providing the surface boundary conditions, 112 followed by the description of the atmospheric pressure and the river runoff. 113 Next, the scheme for interpolation on the fly is described. 90 114 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}),115 One of these is modification by icebergs (see \autoref{sec:SBC_ICB_icebergs}), 92 116 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}), 117 Another example of modification is that due to the ice shelf melting/freezing (see \autoref{sec:SBC_isf}), 94 118 which provides additional sources of fresh water. 95 119 96 120 121 97 122 % ================================================================ 98 123 % Surface boundary condition for the ocean 99 124 % ================================================================ 100 125 \section{Surface boundary condition for the ocean} 101 \label{sec:SBC_ general}126 \label{sec:SBC_ocean} 102 127 103 128 The surface ocean stress is the stress exerted by the wind and the sea-ice on the ocean. 104 129 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}).130 the momentum vertical mixing trend (see \autoref{eq:DYN_zdf_sbc} in \autoref{sec:DYN_zdf}). 106 131 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.132 \ie\ resolved onto the model (\textbf{i},\textbf{j}) direction at $u$- and $v$-points. 108 133 109 134 The surface heat flux is decomposed into two parts, a non solar and a solar heat flux, 110 135 $Q_{ns}$ and $Q_{sr}$, respectively. 111 136 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).137 (\ie\ the sum of sensible, latent and long wave heat fluxes plus 138 the heat content of the mass exchange between the ocean and sea-ice). 114 139 It is applied in \mdl{trasbc} module as a surface boundary condition trend of 115 140 the first level temperature time evolution equation 116 (see \autoref{eq: tra_sbc} and \autoref{eq:tra_sbc_lin} in \autoref{subsec:TRA_sbc}).141 (see \autoref{eq:TRA_sbc} and \autoref{eq:TRA_sbc_lin} in \autoref{subsec:TRA_sbc}). 117 142 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.}.143 It is applied as a 3D trend of the temperature equation (\mdl{traqsr} module) when 144 \np{ln\_traqsr}\forcode{=.true.}. 120 145 The way the light penetrates inside the water column is generally a sum of decreasing exponentials 121 (see \autoref{subsec:TRA_qsr}). 146 (see \autoref{subsec:TRA_qsr}). 122 147 123 148 The surface freshwater budget is provided by the \textit{emp} field. 124 149 It represents the mass flux exchanged with the atmosphere (evaporation minus precipitation) and 125 150 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 151 It affects the ocean in two different ways: 152 $(i)$ it changes the volume of the ocean, and therefore appears in the sea surface height equation as %GS: autoref ssh equation to be added 153 a volume flux, and 129 154 $(ii)$ 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.155 the mass exchanged with atmosphere, sea-ice and ice shelves. 131 156 132 157 133 158 %\colorbox{yellow}{Miss: } 134 159 % 135 %A extensive description of all namsbc namelist (parameter that have to be 160 %A extensive description of all namsbc namelist (parameter that have to be 136 161 %created!) 137 162 % 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-ice163 %Especially the \np{nn\_fsbc}, the \mdl{sbc\_oce} module (fluxes + mean sst sss ssu 164 %ssv) \ie\ information required by flux computation or sea-ice 140 165 % 141 %\mdl{sbc\_oce} containt the definition in memory of the 7 fields (6+runoff), add 166 %\mdl{sbc\_oce} containt the definition in memory of the 7 fields (6+runoff), add 142 167 %a word on runoff: included in surface bc or add as lateral obc{\ldots}. 143 168 % 144 169 %Sbcmod manage the ``providing'' (fourniture) to the ocean the 7 fields 145 170 % 146 %Fluxes update only each nf {\_}sbc time step (namsbc) explain relation147 %between nf {\_}sbc and nf{\_}ice, do we define nf{\_}blk??? ? only one148 %nf {\_}sbc171 %Fluxes update only each nf\_sbc time step (namsbc) explain relation 172 %between nf\_sbc and nf\_ice, do we define nf\_blk??? ? only one 173 %nf\_sbc 149 174 % 150 175 %Explain here all the namlist namsbc variable{\ldots}. 151 % 176 % 152 177 % explain : use or not of surface currents 153 178 % … … 155 180 156 181 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}), and159 it is these averaged fields which are used to computes the surface fluxes at a frequency of \np{nn\_fsbc} time-step.182 the surface currents, temperature and salinity. 183 These variables are averaged over \np{nn\_fsbc} time-step (\autoref{tab:SBC_ssm}), and 184 these averaged fields are used to compute the surface fluxes at the frequency of \np{nn\_fsbc} time-steps. 160 185 161 186 162 187 %-------------------------------------------------TABLE--------------------------------------------------- 163 188 \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} 189 \centering 190 \begin{tabular}{|l|l|l|l|} 191 \hline 192 Variable description & Model variable & Units & point \\ 193 \hline 194 i-component of the surface current & ssu\_m & $m.s^{-1}$ & U \\ 195 \hline 196 j-component of the surface current & ssv\_m & $m.s^{-1}$ & V \\ 197 \hline 198 Sea surface temperature & sst\_m & \r{}$K$ & T \\\hline 199 Sea surface salinty & sss\_m & $psu$ & T \\ \hline 200 \end{tabular} 201 \caption[Ocean variables provided to the surface module)]{ 202 Ocean variables provided to the surface module (\texttt{SBC}). 203 The variable are averaged over \protect\np{nn\_fsbc} time-step, 204 \ie\ the frequency of computation of surface fluxes.} 205 \label{tab:SBC_ssm} 180 206 \end{table} 181 207 %-------------------------------------------------------------------------------------------------------------- 182 208 183 %\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 209 %\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 210 211 212 213 % ================================================================ 214 % Input Data 188 215 % ================================================================ 189 216 \section{Input data generic interface} … … 191 218 192 219 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:220 (2D or 3D fields, like surface forcing or ocean T and S) are specified in \NEMO. 221 This task is achieved by \mdl{fldread}. 222 The module is designed with four main objectives in mind: 196 223 \begin{enumerate} 197 224 \item 198 optionally provide a time interpolation of the input data atmodel time-step, whatever their input frequency is,225 optionally provide a time interpolation of the input data every specified model time-step, whatever their input frequency is, 199 226 and according to the different calendars available in the model. 200 227 \item … … 204 231 \item 205 232 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 result s the user haveonly to fill in for each variable a structure in the namelist file to233 limiting the number of prerequisite informations. 234 \end{enumerate} 235 236 As a result, the user has only to fill in for each variable a structure in the namelist file to 210 237 define the input data file and variable names, the frequency of the data (in hours or months), 211 238 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.239 and three additional parameters for the on-the-fly interpolation. 213 240 When adding a new input variable, the developer has to add the associated structure in the namelist, 214 241 read this information by mirroring the namelist read in \rou{sbc\_blk\_init} for example, 215 242 and simply call \rou{fld\_read} to obtain the desired input field at the model time-step and grid points. 216 243 217 The only constraints are that the input file is a NetCDF file, the file name follows a nomenclature 244 The only constraints are that the input file is a NetCDF file, the file name follows a nomenclature 218 245 (see \autoref{subsec:SBC_fldread}), the period it cover is one year, month, week or day, and, 219 246 if on-the-fly interpolation is used, a file of weights must be supplied (see \autoref{subsec:SBC_iof}). 220 247 221 248 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='./'. 249 the code is executed, then the user can set the \np{cn\_dir} to the pathway leading to the data. 250 By default, the data are assumed to be in the same directory as the executable, so that cn\_dir='./'. 251 224 252 225 253 % ------------------------------------------------------------------------------------------------------------- 226 254 % Input Data specification (\mdl{fldread}) 227 255 % ------------------------------------------------------------------------------------------------------------- 228 \subsection[Input data specification (\textit{fldread.F90})] 229 {Input data specification (\protect\mdl{fldread})} 256 \subsection[Input data specification (\textit{fldread.F90})]{Input data specification (\protect\mdl{fldread})} 230 257 \label{subsec:SBC_fldread} 231 258 232 259 The structure associated with an input variable contains the following information: 233 260 \begin{forlines} 234 ! file name ! frequency (hours) ! variable ! time interp. ! clim ! 'yearly'/ ! weights ! rotation ! land/sea mask ! 261 ! file name ! frequency (hours) ! variable ! time interp. ! clim ! 'yearly'/ ! weights ! rotation ! land/sea mask ! 235 262 ! ! (if <0 months) ! name ! (logical) ! (T/F) ! 'monthly' ! filename ! pairing ! filename ! 236 263 \end{forlines} 237 where 238 \begin{description} 264 where 265 \begin{description} 239 266 \item[File name]: 240 the stem name of the NetCDF file to be open .267 the stem name of the NetCDF file to be opened. 241 268 This stem will be completed automatically by the model, with the addition of a '.nc' at its end and 242 269 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 to270 \autoref{tab:SBC_fldread} provides the resulting file name in all possible cases according to 244 271 whether it is a climatological file or not, and to the open/close frequency (see below for definition). 245 272 246 273 %--------------------------------------------------TABLE-------------------------------------------------- 247 274 \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. 275 \centering 276 \begin{tabular}{|l|c|c|c|} 277 \hline 278 & daily or weekLL & monthly & yearly \\ 279 \hline 280 \np{clim}\forcode{=.false.} & fn\_yYYYYmMMdDD.nc & fn\_yYYYYmMM.nc & fn\_yYYYY.nc \\ 281 \hline 282 \np{clim}\forcode{=.true.} & not possible & fn\_m??.nc & fn \\ 283 \hline 284 \end{tabular} 285 \caption[Naming nomenclature for climatological or interannual input file]{ 286 Naming nomenclature for climatological or interannual input file, 287 as a function of the open/close frequency. 259 288 The stem name is assumed to be 'fn'. 260 289 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', 290 (\ie\ 'sun','sat','fri','thu','wed','tue','mon'). 291 The 'YYYY', 'MM' and 'DD' should be replaced by the actual year/month/day, 292 always coded with 4 or 2 digits. 293 Note that (1) in mpp, if the file is split over each subdomain, 294 the suffix '.nc' is replaced by '\_PPPP.nc', 264 295 where 'PPPP' is the process number coded with 4 digits; 265 (2) when using AGRIF, the prefix '\_N' is added to files, where 'N' 296 (2) when using AGRIF, the prefix '\_N' is added to files, where 'N' is the child grid number. 266 297 } 298 \label{tab:SBC_fldread} 267 299 \end{table} 268 300 %-------------------------------------------------------------------------------------------------------------- 269 301 270 302 271 303 \item[Record frequency]: … … 273 305 Its unit is in hours if it is positive (for example 24 for daily forcing) or in months if negative 274 306 (for example -1 for monthly forcing or -12 for annual forcing). 275 Note that this frequency must reallybe an integer and not a real.276 On some computers, set ing it to '24.' can be interpreted as 240!307 Note that this frequency must REALLY be an integer and not a real. 308 On some computers, setting it to '24.' can be interpreted as 240! 277 309 278 310 \item[Variable name]: … … 285 317 00h00'00'' to 23h59'59". 286 318 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.319 Records are assumed to be dated at the middle of the forcing period. 288 320 For example, when using a daily forcing with time interpolation, 289 linear interpolation will be performed between mid-day of two consecutive days. 321 linear interpolation will be performed between mid-day of two consecutive days. 290 322 291 323 \item[Climatological forcing]: 292 324 a logical to specify if a input file contains climatological forcing which can be cycle in time, 293 325 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.326 the period covered by the simulation exceeds the one of the file. 327 See the above file naming strategy which impacts the expected name of the file to be opened. 296 328 297 329 \item[Open/close frequency]: … … 302 334 Files are assumed to contain data from the beginning of the open/close period. 303 335 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. 336 the experiment is not starting at the beginning of the year. 305 337 306 338 \item[Others]: … … 315 347 the date of the records read in the input files. 316 348 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 349 For example, for an experiment starting at 0h00'00" with a one-hour time-step, 318 350 a time interpolation will be performed at the following time: 0h30'00", 1h30'00", 2h30'00", etc. 319 351 However, for forcing data related to the surface module, 320 352 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 atthe middle of \np{nn\_fsbc} time-step period.323 In the previous example, this leads to: 1h30'00", 4h30'00", 7h30'00", etc. \\ 353 For example with \np{nn\_fsbc}\forcode{=3}, the surface module will be called at time-steps 1, 4, 7, etc. 354 The date used for the time interpolation is thus redefined to the middle of \np{nn\_fsbc} time-step period. 355 In the previous example, this leads to: 1h30'00", 4h30'00", 7h30'00", etc. \\ 324 356 (2) For code readablility and maintenance issues, we don't take into account the NetCDF input file calendar. 325 357 The calendar associated with the forcing field is build according to the information provided by 326 358 user in the record frequency, the open/close frequency and the type of temporal interpolation. 327 359 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". \\360 start Jan 1st at 12h00'00" and end Dec 31st at 12h00'00". \\ 329 361 (3) If a time interpolation is requested, the code will pick up the needed data in the previous (next) file when 330 362 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'', 363 For example, if the input file specifications are ''yearly, containing daily data to be interpolated in time'', 332 364 the values given by the code between 00h00'00" and 11h59'59" on Jan 1st will be interpolated values between 333 365 Dec 31st 12h00'00" and Jan 1st 12h00'00". 334 366 If the forcing is climatological, Dec and Jan will be keep-up from the same year. 335 367 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.368 the open/close period, the code will automatically close the current file and open the next one. 337 369 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.370 an open/close period, we do accept that the previous (next) file is not existing. 339 371 In this case, the time interpolation will be performed between two identical values. 340 372 For example, when starting an experiment on Jan 1st of year Y with yearly files and daily data to be interpolated, 341 373 we do accept that the file related to year Y-1 is not existing. 342 374 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. 375 If the file of year Y-1 exists, the code will read its last record. 344 376 Therefore, this file can contain only one record corresponding to Dec 31st, 345 377 a useful feature for user considering that it is too heavy to manipulate the complete file for year Y-1. … … 354 386 Interpolation on the Fly allows the user to supply input files required for the surface forcing on 355 387 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 to388 To do this, he or she must supply, in addition to the source data file(s), a file of weights to be used to 357 389 interpolate from the data grid to the model grid. 358 390 The original development of this code used the SCRIP package 359 391 (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 in392 In principle, any package such as CDO can be used to generate the weights, but the variables in 361 393 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 .394 Two methods are currently available: bilinear and bicubic interpolations. 363 395 Prior to the interpolation, providing a land/sea mask file, the user can decide to remove land points from 364 396 the input file and substitute the corresponding values with the average of the 8 neighbouring points in … … 366 398 Only "sea points" are considered for the averaging. 367 399 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. 372 400 The netcdf land/sea mask variable name must be 'LSM' and must have the same horizontal and vertical dimensions as 401 the associated variables and should be equal to 1 over land and 0 elsewhere. 402 The procedure can be recursively applied by setting nn\_lsm > 1 in namsbc namelist. 403 Note that nn\_lsm=0 forces the code to not apply the procedure, even if a land/sea mask file is supplied. 404 405 406 % ------------------------------------------------------------------------------------------------------------- 407 % Bilinear interpolation 408 % ------------------------------------------------------------------------------------------------------------- 373 409 \subsubsection{Bilinear interpolation} 374 410 \label{subsec:SBC_iof_bilinear} … … 376 412 The input weights file in this case has two sets of variables: 377 413 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.414 The "src" variables correspond to the point in the input grid to which the weight "wgt" is applied. 379 415 Each src value is an integer corresponding to the index of a point in the input grid when 380 416 written as a one dimensional array. … … 392 428 and wgt(1) corresponds to variable "wgt01" for example. 393 429 430 431 % ------------------------------------------------------------------------------------------------------------- 432 % Bicubic interpolation 433 % ------------------------------------------------------------------------------------------------------------- 394 434 \subsubsection{Bicubic interpolation} 395 435 \label{subsec:SBC_iof_bicubic} 396 436 397 Again there are two sets of variables: "src" and "wgt".398 But in this case there are 16 of each.437 Again, there are two sets of variables: "src" and "wgt". 438 But in this case, there are 16 of each. 399 439 The symbolic algorithm used to calculate values on the model grid is now: 400 440 … … 402 442 \begin{split} 403 443 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 + 444 + \sum_{k=5 }^{8 } {wgt(k)\left.\frac{\partial f}{\partial i}\right| _{idx(src(k))} } \\ 445 +& \sum_{k=9 }^{12} {wgt(k)\left.\frac{\partial f}{\partial j}\right| _{idx(src(k))} } 446 + \sum_{k=13}^{16} {wgt(k)\left.\frac{\partial ^2 f}{\partial i \partial j}\right| _{idx(src(k))} } 407 447 \end{split} 408 448 \] 409 449 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. 411 450 the spatial dependency has been included into the weights. 451 452 453 % ------------------------------------------------------------------------------------------------------------- 454 % Implementation 455 % ------------------------------------------------------------------------------------------------------------- 412 456 \subsubsection{Implementation} 413 457 \label{subsec:SBC_iof_imp} … … 421 465 inspecting a global attribute stored in the weights input file. 422 466 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.467 If it is negative, the input non-model grid is assumed to be not cyclic. 424 468 If zero or greater, then the value represents the number of columns that overlap. 425 469 $E.g.$ if the input grid has columns at longitudes 0, 1, 2, .... , 359, then ew\_wrap should be set to 0; 426 470 if longitudes are 0.5, 2.5, .... , 358.5, 360.5, 362.5, ew\_wrap should be 2. 427 471 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 and472 In this case, the \rou{fld\_read} routine defaults ew\_wrap to value 0 and 429 473 therefore the grid is assumed to be cyclic with no overlapping columns. 430 (In fact this only matters when bicubic interpolation is required.)474 (In fact, this only matters when bicubic interpolation is required.) 431 475 Note that no testing is done to check the validity in the model, 432 476 since there is no way of knowing the name used for the longitude variable, … … 445 489 or is a copy of one from the first few columns on the opposite side of the grid (cyclical case). 446 490 491 492 % ------------------------------------------------------------------------------------------------------------- 493 % Limitations 494 % ------------------------------------------------------------------------------------------------------------- 447 495 \subsubsection{Limitations} 448 496 \label{subsec:SBC_iof_lim} 449 497 450 \begin{enumerate} 451 \item 452 The case where input data grids are not logically rectangular has not been tested.498 \begin{enumerate} 499 \item 500 The case where input data grids are not logically rectangular (irregular grid case) has not been tested. 453 501 \item 454 502 This code is not guaranteed to produce positive definite answers from positive definite inputs when … … 471 519 (see the directory NEMOGCM/TOOLS/WEIGHTS). 472 520 521 473 522 % ------------------------------------------------------------------------------------------------------------- 474 523 % Standalone Surface Boundary Condition Scheme 475 524 % ------------------------------------------------------------------------------------------------------------- 476 \subsection{Standalone surface boundary condition scheme} 477 \label{subsec:SAS_iof} 478 479 %---------------------------------------namsbc_ana-------------------------------------------------- 480 481 \nlst{namsbc_sas} 525 \subsection{Standalone surface boundary condition scheme (SAS)} 526 \label{subsec:SBC_SAS} 527 528 %---------------------------------------namsbc_sas-------------------------------------------------- 529 530 \begin{listing} 531 \nlst{namsbc_sas} 532 \caption{\forcode{&namsbc_sas}} 533 \label{lst:namsbc_sas} 534 \end{listing} 482 535 %-------------------------------------------------------------------------------------------------------------- 483 536 484 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. 537 In some circumstances, it may be useful to avoid calculating the 3D temperature, 538 salinity and velocity fields and simply read them in from a previous run or receive them from OASIS. 486 539 For example: 487 540 … … 497 550 Spinup of the iceberg floats 498 551 \item 499 Ocean/sea-ice simulation with both m edia running in parallel (\np{ln\_mixcpl}\forcode{ =.true.})552 Ocean/sea-ice simulation with both models running in parallel (\np{ln\_mixcpl}\forcode{=.true.}) 500 553 \end{itemize} 501 554 502 The Stand Alone Surface scheme provides this utility.503 Its options are defined through the \n gn{namsbc\_sas} namelist variables.555 The Standalone Surface scheme provides this capacity. 556 Its options are defined through the \nam{sbc\_sas} namelist variables. 504 557 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).558 However, no namelist parameters need be changed from the settings of the previous run (except perhaps nn\_date0). 506 559 In this configuration, a few routines in the standard model are overriden by new versions. 507 560 Routines replaced are: … … 519 572 This has been cut down and now only calculates surface forcing and the ice model required. 520 573 New surface modules that can function when only the surface level of the ocean state is defined can also be added 521 (\eg icebergs).574 (\eg\ icebergs). 522 575 \item 523 576 \mdl{daymod}: … … 525 578 so calls to restart functions have been removed. 526 579 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.580 so the user must check that nn\_date0 in the model namelist is correct for his or her purposes. 528 581 \item 529 582 \mdl{stpctl}: … … 543 596 This module initialises the input files needed for reading temperature, salinity and 544 597 velocity arrays at the surface. 545 These filenames are supplied in namelist namsbc {\_}sas.546 Unfortunately because of limitations with the \mdl{iom} module,598 These filenames are supplied in namelist namsbc\_sas. 599 Unfortunately, because of limitations with the \mdl{iom} module, 547 600 the full 3D fields from the mean files have to be read in and interpolated in time, 548 601 before using just the top level. … … 551 604 552 605 553 % 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})} 606 The user can also choose in the \nam{sbc\_sas} namelist to read the mean (nn\_fsbc time-step) fraction of solar net radiation absorbed in the 1st T level using 607 (\np{ln\_flx}\forcode{=.true.}) and to provide 3D oceanic velocities instead of 2D ones (\np{ln\_flx}\forcode{=.true.}). In that last case, only the 1st level will be read in. 608 609 610 611 % ================================================================ 612 % Flux formulation 613 % ================================================================ 614 \section[Flux formulation (\textit{sbcflx.F90})]{Flux formulation (\protect\mdl{sbcflx})} 590 615 \label{sec:SBC_flx} 591 616 %------------------------------------------namsbc_flx---------------------------------------------------- 592 617 593 \nlst{namsbc_flx} 618 \begin{listing} 619 \nlst{namsbc_flx} 620 \caption{\forcode{&namsbc_flx}} 621 \label{lst:namsbc_flx} 622 \end{listing} 594 623 %------------------------------------------------------------------------------------------------------------- 595 624 596 In the flux formulation (\np{ln\_flx}\forcode{ =.true.}),625 In the flux formulation (\np{ln\_flx}\forcode{=.true.}), 597 626 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,627 The user has to define in the namelist \nam{sbc\_flx} the name of the file, 599 628 the name of the variable read in the file, the time frequency at which it is given (in hours), 600 629 and a logical setting whether a time interpolation to the model time step is required for this field. … … 605 634 606 635 636 607 637 % ================================================================ 608 638 % Bulk formulation 609 639 % ================================================================ 610 \section[Bulk formulation {(\textit{sbcblk\{\_core,\_clio\}.F90})}] 611 {Bulk formulation {(\protect\mdl{sbcblk\_core}, \protect\mdl{sbcblk\_clio})}} 640 \section[Bulk formulation (\textit{sbcblk.F90})]{Bulk formulation (\protect\mdl{sbcblk})} 612 641 \label{sec:SBC_blk} 613 614 In the bulk formulation, the surface boundary condition fields are computed using bulk formulae and atmospheric fields and ocean (and ice) variables. 642 %---------------------------------------namsbc_blk-------------------------------------------------- 643 644 \begin{listing} 645 \nlst{namsbc_blk} 646 \caption{\forcode{&namsbc_blk}} 647 \label{lst:namsbc_blk} 648 \end{listing} 649 %-------------------------------------------------------------------------------------------------------------- 650 651 In the bulk formulation, the surface boundary condition fields are computed with bulk formulae using atmospheric fields 652 and ocean (and sea-ice) variables averaged over \np{nn\_fsbc} time-step. 615 653 616 654 The atmospheric fields used depend on the bulk formulae used. 617 Two bulk formulations are available: 618 the CORE and the CLIO bulk formulea. 655 In forced mode, when a sea-ice model is used, a specific bulk formulation is used. 656 Therefore, different bulk formulae are used for the turbulent fluxes computation 657 over the ocean and over sea-ice surface. 658 For the ocean, four bulk formulations are available thanks to the \href{https://brodeau.github.io/aerobulk/}{Aerobulk} package (\citet{brodeau.barnier.ea_JPO16}): 659 the NCAR (formerly named CORE), COARE 3.0, COARE 3.5 and ECMWF bulk formulae. 619 660 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: 661 \np{ln\_NCAR}, \np{ln\_COARE\_3p0}, \np{ln\_COARE\_3p5} and \np{ln\_ECMWF}. 662 For sea-ice, three possibilities can be selected: 663 a constant transfer coefficient (1.4e-3; default value), \citet{lupkes.gryanik.ea_JGR12} (\np{ln\_Cd\_L12}), and \citet{lupkes.gryanik_JGR15} (\np{ln\_Cd\_L15}) parameterizations 664 665 Common options are defined through the \nam{sbc\_blk} namelist variables. 666 The required 9 input fields are: 650 667 651 668 %--------------------------------------------------TABLE-------------------------------------------------- 652 669 \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 670 \centering 671 \begin{tabular}{|l|c|c|c|} 672 \hline 673 Variable description & Model variable & Units & point \\ 674 \hline 675 i-component of the 10m air velocity & utau & $m.s^{-1}$ & T \\ 676 \hline 677 j-component of the 10m air velocity & vtau & $m.s^{-1}$ & T \\ 678 \hline 679 10m air temperature & tair & \r{}$K$ & T \\ 680 \hline 681 Specific humidity & humi & \% & T \\ 682 \hline 683 Incoming long wave radiation & qlw & $W.m^{-2}$ & T \\ 684 \hline 685 Incoming short wave radiation & qsr & $W.m^{-2}$ & T \\ 686 \hline 687 Total precipitation (liquid + solid) & precip & $Kg.m^{-2}.s^{-1}$ & T \\ 688 \hline 689 Solid precipitation & snow & $Kg.m^{-2}.s^{-1}$ & T \\ 690 \hline 691 Mean sea-level pressure & slp & $hPa$ & T \\ 692 \hline 666 693 \end{tabular} 667 \ end{center}694 \label{tab:SBC_BULK} 668 695 \end{table} 669 696 %-------------------------------------------------------------------------------------------------------------- … … 675 702 The \np{sn\_wndi}, \np{sn\_wndj}, \np{sn\_qsr}, \np{sn\_qlw}, \np{sn\_tair}, \np{sn\_humi}, \np{sn\_prec}, 676 703 \np{sn\_snow}, \np{sn\_tdif} parameters describe the fields and the way they have to be used 677 (spatial and temporal interpolations). 704 (spatial and temporal interpolations). 678 705 679 706 \np{cn\_dir} is the directory of location of bulk files … … 682 709 \np{rn\_zu}: is the height of wind measurements (m) 683 710 684 Three multiplicative factors are available s:685 \np{rn\_pfac} and \np{rn\_efac} allow sto adjust (if necessary) the global freshwater budget by711 Three multiplicative factors are available: 712 \np{rn\_pfac} and \np{rn\_efac} allow to adjust (if necessary) the global freshwater budget by 686 713 increasing/reducing the precipitations (total and snow) and or evaporation, respectively. 687 714 The third one,\np{rn\_vfac}, control to which extend the ice/ocean velocities are taken into account in 688 715 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 %-------------------------------------------------------------------------------------------------------------- 716 Its range must be between zero and one, and it is recommended to set it to 0 at low-resolution (ORCA2 configuration). 729 717 730 718 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}). 719 the namsbc\_blk namelist (see \autoref{subsec:SBC_fldread}). 720 721 722 % ------------------------------------------------------------------------------------------------------------- 723 % Ocean-Atmosphere Bulk formulae 724 % ------------------------------------------------------------------------------------------------------------- 725 \subsection[Ocean-Atmosphere Bulk formulae (\textit{sbcblk\_algo\_coare.F90, sbcblk\_algo\_coare3p5.F90, sbcblk\_algo\_ecmwf.F90, sbcblk\_algo\_ncar.F90})]{Ocean-Atmosphere Bulk formulae (\mdl{sbcblk\_algo\_coare}, \mdl{sbcblk\_algo\_coare3p5}, \mdl{sbcblk\_algo\_ecmwf}, \mdl{sbcblk\_algo\_ncar})} 726 \label{subsec:SBC_blk_ocean} 727 728 Four different bulk algorithms are available to compute surface turbulent momentum and heat fluxes over the ocean. 729 COARE 3.0, COARE 3.5 and ECMWF schemes mainly differ by their roughness lenghts computation and consequently 730 their neutral transfer coefficients relationships with neutral wind. 731 \begin{itemize} 732 \item 733 NCAR (\np{ln\_NCAR}\forcode{=.true.}): 734 The NCAR bulk formulae have been developed by \citet{large.yeager_rpt04}. 735 They have been designed to handle the NCAR forcing, a mixture of NCEP reanalysis and satellite data. 736 They use an inertial dissipative method to compute the turbulent transfer coefficients 737 (momentum, sensible heat and evaporation) from the 10m wind speed, air temperature and specific humidity. 738 This \citet{large.yeager_rpt04} dataset is available through 739 the \href{http://nomads.gfdl.noaa.gov/nomads/forms/mom4/NCAR.html}{GFDL web site}. 740 Note that substituting ERA40 to NCEP reanalysis fields does not require changes in the bulk formulea themself. 741 This is the so-called DRAKKAR Forcing Set (DFS) \citep{brodeau.barnier.ea_OM10}. 742 \item 743 COARE 3.0 (\np{ln\_COARE\_3p0}\forcode{=.true.}): 744 See \citet{fairall.bradley.ea_JC03} for more details 745 \item 746 COARE 3.5 (\np{ln\_COARE\_3p5}\forcode{=.true.}): 747 See \citet{edson.jampana.ea_JPO13} for more details 748 \item 749 ECMWF (\np{ln\_ECMWF}\forcode{=.true.}): 750 Based on \href{https://www.ecmwf.int/node/9221}{IFS (Cy31)} implementation and documentation. 751 Surface roughness lengths needed for the Obukhov length are computed following \citet{beljaars_QJRMS95}. 752 \end{itemize} 753 754 % ------------------------------------------------------------------------------------------------------------- 755 % Ice-Atmosphere Bulk formulae 756 % ------------------------------------------------------------------------------------------------------------- 757 \subsection{Ice-Atmosphere Bulk formulae} 758 \label{subsec:SBC_blk_ice} 759 760 Surface turbulent fluxes between sea-ice and the atmosphere can be computed in three different ways: 761 762 \begin{itemize} 763 \item 764 Constant value (\np{constant\ value}\forcode{ Cd_ice = 1.4e-3 }): 765 default constant value used for momentum and heat neutral transfer coefficients 766 \item 767 \citet{lupkes.gryanik.ea_JGR12} (\np{ln\_Cd\_L12}\forcode{=.true.}): 768 This scheme adds a dependency on edges at leads, melt ponds and flows 769 of the constant neutral air-ice drag. After some approximations, 770 this can be resumed to a dependency on ice concentration (A). 771 This drag coefficient has a parabolic shape (as a function of ice concentration) 772 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. 773 It is theoretically applicable to all ice conditions (not only MIZ). 774 \item 775 \citet{lupkes.gryanik_JGR15} (\np{ln\_Cd\_L15}\forcode{=.true.}): 776 Alternative turbulent transfer coefficients formulation between sea-ice 777 and atmosphere with distinct momentum and heat coefficients depending 778 on sea-ice concentration and atmospheric stability (no melt-ponds effect for now). 779 The parameterization is adapted from ECHAM6 atmospheric model. 780 Compared to Lupkes2012 scheme, it considers specific skin and form drags 781 to compute neutral transfer coefficients for both heat and momentum fluxes. 782 Atmospheric stability effect on transfer coefficient is also taken into account. 783 \end{itemize} 784 785 732 786 733 787 % ================================================================ 734 788 % Coupled formulation 735 789 % ================================================================ 736 \section[Coupled formulation (\textit{sbccpl.F90})] 737 {Coupled formulation (\protect\mdl{sbccpl})} 790 \section[Coupled formulation (\textit{sbccpl.F90})]{Coupled formulation (\protect\mdl{sbccpl})} 738 791 \label{sec:SBC_cpl} 739 792 %------------------------------------------namsbc_cpl---------------------------------------------------- 740 793 741 \nlst{namsbc_cpl} 794 \begin{listing} 795 \nlst{namsbc_cpl} 796 \caption{\forcode{&namsbc_cpl}} 797 \label{lst:namsbc_cpl} 798 \end{listing} 742 799 %------------------------------------------------------------------------------------------------------------- 743 800 744 801 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 ,802 the fluxes are provided by the OASIS coupler at a frequency which is defined in the OASIS coupler namelist, 746 803 while sea and ice surface temperature, ocean and ice albedo, and ocean currents are sent to 747 804 the atmospheric component. 748 805 749 806 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 807 It is currently interfaced with OASIS-3-MCT versions 1 to 4 (\key{oasis3}). 808 An additional specific CPP key (\key{oa3mct\_v1v2}) is needed for OASIS-3-MCT versions 1 and 2. 809 It has been successfully used to interface \NEMO\ to most of the European atmospheric GCM 752 810 (ARPEGE, ECHAM, ECMWF, HadAM, HadGAM, LMDz), as well as to \href{http://wrf-model.org/}{WRF} 753 811 (Weather Research and Forecasting Model). 754 812 755 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}. 813 When PISCES biogeochemical model (\key{top}) is also used in the coupled system, 814 the whole carbon cycle is computed. 760 815 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} ).816 (and need to be activated in \nam{sbc\_cpl} ). 762 817 763 818 The namelist above allows control of various aspects of the coupling fields (particularly for vectors) and 764 819 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 by820 When indicating a multi-category coupling field in \nam{sbc\_cpl}, the number of categories will be determined by 766 821 the number used in the sea ice model. 767 In some limited cases it may be possible to specify single category coupling fields even when822 In some limited cases, it may be possible to specify single category coupling fields even when 768 823 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. 824 in this case, the user should examine the code to be sure the assumptions made are satisfactory. 825 In cases where this is definitely not possible, the model should abort with an error message. 826 773 827 774 828 … … 776 830 % Atmospheric pressure 777 831 % ================================================================ 778 \section[Atmospheric pressure (\textit{sbcapr.F90})] 779 {Atmospheric pressure (\protect\mdl{sbcapr})} 832 \section[Atmospheric pressure (\textit{sbcapr.F90})]{Atmospheric pressure (\protect\mdl{sbcapr})} 780 833 \label{sec:SBC_apr} 781 834 %------------------------------------------namsbc_apr---------------------------------------------------- 782 835 783 \nlst{namsbc_apr} 836 \begin{listing} 837 \nlst{namsbc_apr} 838 \caption{\forcode{&namsbc_apr}} 839 \label{lst:namsbc_apr} 840 \end{listing} 784 841 %------------------------------------------------------------------------------------------------------------- 785 842 786 843 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)844 (\np{ln\_apr\_dyn}\forcode{=.true.}, \nam{sbc} namelist). 845 The input atmospheric forcing defined via \np{sn\_apr} structure (\nam{sbc\_apr} namelist) 789 846 can be interpolated in time to the model time step, and even in space when the interpolation on-the-fly is used. 790 847 When used to force the dynamics, the atmospheric pressure is further transformed into … … 796 853 where $P_{atm}$ is the atmospheric pressure and $P_o$ a reference atmospheric pressure. 797 854 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.855 In this case, $P_o$ is set to the value of $P_{atm}$ averaged over the ocean domain, 856 \ie\ the mean value of $\eta_{ib}$ is kept to zero at all time steps. 800 857 801 858 The gradient of $\eta_{ib}$ is added to the RHS of the ocean momentum equation (see \mdl{dynspg} for the ocean). 802 859 For sea-ice, the sea surface height, $\eta_m$, which is provided to the sea ice model is set to $\eta - \eta_{ib}$ 803 860 (see \mdl{sbcssr} module). 804 $\eta_{ib}$ can be setin the output.861 $\eta_{ib}$ can be written in the output. 805 862 This can simplify altimetry data and model comparison as 806 863 inverse barometer sea surface height is usually removed from these date prior to their distribution. 807 864 808 865 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: 866 the equivalent inverse barometer sea surface height $\eta_{ib}$ can be added to BDY ssh data: 810 867 \np{ln\_apr\_obc} might be set to true. 811 868 869 870 812 871 % ================================================================ 813 872 % Surface Tides Forcing 814 873 % ================================================================ 815 \section[Surface tides (\textit{sbctide.F90})] 816 {Surface tides (\protect\mdl{sbctide})} 874 \section[Surface tides (\textit{sbctide.F90})]{Surface tides (\protect\mdl{sbctide})} 817 875 \label{sec:SBC_tide} 818 876 819 877 %------------------------------------------nam_tide--------------------------------------- 820 878 821 \nlst{nam_tide} 879 \begin{listing} 880 \nlst{nam_tide} 881 \caption{\forcode{&nam_tide}} 882 \label{lst:nam_tide} 883 \end{listing} 822 884 %----------------------------------------------------------------------------------------- 823 885 824 886 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 \n gn{nam\_tide}.826 This translates as an additional barotropic force in the momentum equations \ref{eq:PE_dyn} such that:887 is activated if \np{ln\_tide} and \np{ln\_tide\_pot} are both set to \forcode{.true.} in \nam{\_tide}. 888 This translates as an additional barotropic force in the momentum \autoref{eq:MB_PE_dyn} such that: 827 889 \[ 828 % \label{eq: PE_dyn_tides}890 % \label{eq:SBC_PE_dyn_tides} 829 891 \frac{\partial {\mathrm {\mathbf U}}_h }{\partial t}= ... 830 892 +g\nabla (\Pi_{eq} + \Pi_{sal}) … … 832 894 where $\Pi_{eq}$ stands for the equilibrium tidal forcing and 833 895 $\Pi_{sal}$ is a self-attraction and loading term (SAL). 834 896 835 897 The equilibrium tidal forcing is expressed as a sum over a subset of 836 898 constituents chosen from the set of available tidal constituents 837 defined in file \ rou{SBC/tide.h90} (this comprises the tidal899 defined in file \hf{SBC/tide} (this comprises the tidal 838 900 constituents \textit{M2, N2, 2N2, S2, K2, K1, O1, Q1, P1, M4, Mf, Mm, 839 901 Msqm, Mtm, S1, MU2, NU2, L2}, and \textit{T2}). Individual 840 902 constituents are selected by including their names in the array 841 \np{clname} in \n gn{nam\_tide} (e.g., \np{clname(1) = 'M2',842 clname(2)='S2'} to select solely the tidal consituents \textit{M2}903 \np{clname} in \nam{\_tide} (e.g., \np{clname}\forcode{(1)='M2', } 904 \np{clname}\forcode{(2)='S2'} to select solely the tidal consituents \textit{M2} 843 905 and \textit{S2}). Optionally, when \np{ln\_tide\_ramp} is set to 844 906 \forcode{.true.}, the equilibrium tidal forcing can be ramped up … … 850 912 discussion about the practical implementation of this term). 851 913 Nevertheless, the complex calculations involved would make this 852 computationally too expensive. 914 computationally too expensive. Here, two options are available: 853 915 $\Pi_{sal}$ 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 case916 (\np{ln\_read\_load}\forcode{ =.true.}), or a ``scalar approximation'' can be 917 used (\np{ln\_scal\_load}\forcode{ =.true.}). In the latter case 856 918 \[ 857 919 \Pi_{sal} = \beta \eta, … … 862 924 \forcode{.false.} removes the SAL contribution. 863 925 926 927 864 928 % ================================================================ 865 929 % River runoffs 866 930 % ================================================================ 867 \section[River runoffs (\textit{sbcrnf.F90})] 868 {River runoffs (\protect\mdl{sbcrnf})} 931 \section[River runoffs (\textit{sbcrnf.F90})]{River runoffs (\protect\mdl{sbcrnf})} 869 932 \label{sec:SBC_rnf} 870 933 %------------------------------------------namsbc_rnf---------------------------------------------------- 871 934 872 \nlst{namsbc_rnf} 935 \begin{listing} 936 \nlst{namsbc_rnf} 937 \caption{\forcode{&namsbc_rnf}} 938 \label{lst:namsbc_rnf} 939 \end{listing} 873 940 %------------------------------------------------------------------------------------------------------------- 874 941 875 %River runoff generally enters the ocean at a nonzero depth rather than through the surface. 942 %River runoff generally enters the ocean at a nonzero depth rather than through the surface. 876 943 %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 944 %This was the case in \NEMO\ prior to the version 3.3. The switch toward a input of runoff 945 %throughout a nonzero depth has been motivated by the numerical and physical problems 946 %that arise when the top grid cells are of the order of one meter. This situation is common in 947 %coastal modelling and becomes more and more often open ocean and climate modelling 881 948 %\footnote{At least a top cells thickness of 1~meter and a 3 hours forcing frequency are 882 949 %required to properly represent the diurnal cycle \citep{bernie.woolnough.ea_JC05}. see also \autoref{fig:SBC_dcy}.}. 883 950 884 951 885 %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 952 %To do this we need to treat evaporation/precipitation fluxes and river runoff differently in the 953 %\mdl{tra\_sbc} module. We decided to separate them throughout the code, so that the variable 954 %\textit{emp} represented solely evaporation minus precipitation fluxes, and a new 2d variable 955 %rnf was added which represents the volume flux of river runoff (in kg/m2s to remain consistent with 956 %emp). This meant many uses of emp and emps needed to be changed, a list of all modules which use 890 957 %emp or emps and the changes made are below: 891 958 … … 894 961 River runoff generally enters the ocean at a nonzero depth rather than through the surface. 895 962 Many models, however, have traditionally inserted river runoff to the top model cell. 896 This was the case in \NEMO prior to the version 3.3,963 This was the case in \NEMO\ prior to the version 3.3, 897 964 and was combined with an option to increase vertical mixing near the river mouth. 898 965 899 966 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 967 This situation is common in coastal modelling and is becoming more common in open ocean and climate modelling 901 968 \footnote{ 902 969 At least a top cells thickness of 1~meter and a 3 hours forcing frequency are required to … … 909 976 along with the depth (in metres) which the river should be added to. 910 977 911 Namelist variables in \n gn{namsbc\_rnf}, \np{ln\_rnf\_depth}, \np{ln\_rnf\_sal} and978 Namelist variables in \nam{sbc\_rnf}, \np{ln\_rnf\_depth}, \np{ln\_rnf\_sal} and 912 979 \np{ln\_rnf\_temp} control whether the river attributes (depth, salinity and temperature) are read in and used. 913 980 If these are set as false the river is added to the surface box only, assumed to be fresh (0~psu), 914 981 and/or taken as surface temperature respectively. 915 982 916 The runoff value and attributes are read in in sbcrnf. 983 The runoff value and attributes are read in in sbcrnf. 917 984 For temperature -999 is taken as missing data and the river temperature is taken to 918 985 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. 986 For the depth parameter a value of -1 means the river is added to the surface box only, 987 and a value of -999 means the river is added through the entire water column. 921 988 After being read in the temperature and salinity variables are multiplied by the amount of runoff 922 989 (converted into m/s) to give the heat and salt content of the river runoff. … … 925 992 The variable \textit{h\_dep} is then calculated to be the depth (in metres) of 926 993 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).994 (\ie\ the total depth that river water is being added to in the model). 928 995 929 996 The mass/volume addition due to the river runoff is, at each relevant depth level, added to … … 931 998 This increases the diffusion term in the vicinity of the river, thereby simulating a momentum flux. 932 999 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. 1000 and so the river runoff indirectly forces an increase in sea surface height. 934 1001 935 1002 The \textit{hdivn} terms are used in the tracer advection modules to force vertical velocities. … … 944 1011 As such the volume of water does not change, but the water is diluted. 945 1012 946 For the non-linear free surface case (\key{vvl}), no flux is allowed through the surface.1013 For the non-linear free surface case, no flux is allowed through the surface. 947 1014 Instead in the surface box (as well as water moving up from the boxes below) a volume of runoff water is added with 948 1015 no corresponding heat and salt addition and so as happens in the lower boxes there is a dilution effect. … … 953 1020 This is done in the same way for both vvl and non-vvl. 954 1021 The temperature and salinity are increased through the specified depth according to 955 the heat and salt content of the river. 1022 the heat and salt content of the river. 956 1023 957 1024 In the non-linear free surface case (vvl), … … 962 1029 963 1030 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.1031 \ie\ modelling the Baltic flow in and out of the North Sea. 965 1032 When the flow is out of the domain there is no change in temperature and salinity, 966 1033 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 1034 as the ocean water leaving the domain removes heat and salt (at the same concentration) with it. 1035 1036 1037 %\colorbox{yellow}{Nevertheless, Pb of vertical resolution and 3D input : increase vertical mixing near river mouths to mimic a 3D river 971 1038 972 1039 %All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and at the same temperature as the sea surface.} … … 980 1047 %\gmcomment{ word doc of runoffs: 981 1048 % 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. 1049 %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. 1050 %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 1051 985 1052 %The depth option makes it possible to have the river water affecting just the surface layer, throughout depth, or some specified point in between. … … 987 1054 %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 1055 989 %} 1056 1057 990 1058 % ================================================================ 991 1059 % Ice shelf melting 992 1060 % ================================================================ 993 \section[Ice shelf melting (\textit{sbcisf.F90})] 994 {Ice shelf melting (\protect\mdl{sbcisf})} 1061 \section[Ice shelf melting (\textit{sbcisf.F90})]{Ice shelf melting (\protect\mdl{sbcisf})} 995 1062 \label{sec:SBC_isf} 996 1063 %------------------------------------------namsbc_isf---------------------------------------------------- 997 1064 998 \nlst{namsbc_isf} 1065 \begin{listing} 1066 \nlst{namsbc_isf} 1067 \caption{\forcode{&namsbc_isf}} 1068 \label{lst:namsbc_isf} 1069 \end{listing} 999 1070 %-------------------------------------------------------------------------------------------------------- 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}. 1071 1072 The namelist variable in \nam{sbc}, \np{nn\_isf}, controls the ice shelf representation. 1073 Description and result of sensitivity test to \np{nn\_isf} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1002 1074 The different options are illustrated in \autoref{fig:SBC_isf}. 1003 1075 1004 1076 \begin{description} 1005 \item[\np{nn\_isf}\forcode{ = 1}]: 1006 The ice shelf cavity is represented (\np{ln\_isfcav}\forcode{ = .true.} needed). 1077 1078 \item[\np{nn\_isf}\forcode{=1}]: 1079 The ice shelf cavity is represented (\np{ln\_isfcav}\forcode{=.true.} needed). 1007 1080 The fwf and heat flux are depending of the local water properties. 1081 1008 1082 Two different bulk formulae are available: 1009 1083 1010 1084 \begin{description} 1011 \item[\np{nn\_isfblk}\forcode{ =1}]:1085 \item[\np{nn\_isfblk}\forcode{=1}]: 1012 1086 The melt rate is based on a balance between the upward ocean heat flux and 1013 1087 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}]:1088 \item[\np{nn\_isfblk}\forcode{=2}]: 1015 1089 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). 1090 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 1017 1091 A complete description is available in \citet{jenkins_JGR91}. 1018 1092 \end{description} 1019 1093 1020 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1094 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1021 1095 Its thickness is defined by \np{rn\_hisf\_tbl}. 1022 1096 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn\_hisf\_tbl} m. … … 1026 1100 If \np{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 1027 1101 1028 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1102 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1029 1103 There are 3 different ways to compute the exchange coeficient: 1030 1104 \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 \[ 1038 \gamma^{S} = \np{rn\_gammas0} 1039 \] 1105 \item[\np{nn\_gammablk}\forcode{=0}]: 1106 The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}. 1107 \begin{gather*} 1108 % \label{eq:SBC_isf_gamma_iso} 1109 \gamma^{T} = rn\_gammat0 \\ 1110 \gamma^{S} = rn\_gammas0 1111 \end{gather*} 1040 1112 This is the recommended formulation for ISOMIP. 1041 \item[\np{nn\_gammablk}\forcode{ =1}]:1113 \item[\np{nn\_gammablk}\forcode{=1}]: 1042 1114 The salt and heat exchange coefficients are velocity dependent and defined as 1043 \[ 1044 \gamma^{T} = \np{rn\_gammat0} \times u_{*} 1045 \] 1046 \[ 1047 \gamma^{S} = \np{rn\_gammas0} \times u_{*} 1048 \] 1115 \begin{gather*} 1116 \gamma^{T} = rn\_gammat0 \times u_{*} \\ 1117 \gamma^{S} = rn\_gammas0 \times u_{*} 1118 \end{gather*} 1049 1119 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters). 1050 1120 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}]:1121 \item[\np{nn\_gammablk}\forcode{=2}]: 1052 1122 The salt and heat exchange coefficients are velocity and stability dependent and defined as: 1053 1123 \[ 1054 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1124 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1055 1125 \] 1056 1126 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters), 1057 1127 $\Gamma_{Turb}$ the contribution of the ocean stability and 1058 1128 $\Gamma^{T,S}_{Mole}$ 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).1129 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1130 This formulation has not been extensively tested in \NEMO\ (not recommended). 1061 1131 \end{description} 1062 \item[\np{nn\_isf}\forcode{ =2}]:1132 \item[\np{nn\_isf}\forcode{=2}]: 1063 1133 The ice shelf cavity is not represented. 1064 1134 The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 1065 1135 The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 1066 1136 (\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}).1137 (\np{sn\_depmin\_isf}) as in (\np{nn\_isf}\forcode{=3}). 1068 1138 The effective melting length (\np{sn\_Leff\_isf}) is read from a file. 1069 \item[\np{nn\_isf}\forcode{ =3}]:1139 \item[\np{nn\_isf}\forcode{=3}]: 1070 1140 The ice shelf cavity is not represented. 1071 1141 The fwf (\np{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between … … 1073 1143 the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}). 1074 1144 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).1145 \item[\np{nn\_isf}\forcode{=4}]: 1146 The ice shelf cavity is opened (\np{ln\_isfcav}\forcode{=.true.} needed). 1077 1147 However, the fwf is not computed but specified from file \np{sn\_fwfisf}). 1078 1148 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})\\1149 As in \np{nn\_isf}\forcode{=1}, the fluxes are spread over the top boundary layer thickness (\np{rn\_hisf\_tbl})\\ 1080 1150 \end{description} 1081 1151 1082 $\bullet$ \np{nn\_isf}\forcode{ = 1} and \np{nn\_isf}\forcode{ =2} compute a melt rate based on1152 $\bullet$ \np{nn\_isf}\forcode{=1} and \np{nn\_isf}\forcode{=2} compute a melt rate based on 1083 1153 the water mass properties, ocean velocities and depth. 1084 1154 This flux is thus highly dependent of the model resolution (horizontal and vertical), 1085 1155 realism of the water masses onto the shelf ...\\ 1086 1156 1087 $\bullet$ \np{nn\_isf}\forcode{ = 3} and \np{nn\_isf}\forcode{ =4} read the melt rate from a file.1157 $\bullet$ \np{nn\_isf}\forcode{=3} and \np{nn\_isf}\forcode{=4} read the melt rate from a file. 1088 1158 You have total control of the fwf forcing. 1089 1159 This can be useful if the water masses on the shelf are not realistic or 1090 1160 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.\\ 1161 for studies where you need to control your heat and fw input.\\ 1092 1162 1093 1163 The ice shelf melt is implemented as a volume flux as for the runoff. … … 1098 1168 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1099 1169 \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} 1170 \centering 1171 \includegraphics[width=0.66\textwidth]{Fig_SBC_isf} 1172 \caption[Ice shelf location and fresh water flux definition]{ 1173 Illustration of the location where the fwf is injected and 1174 whether or not the fwf is interactif or not depending of \protect\np{nn\_isf}.} 1175 \label{fig:SBC_isf} 1107 1176 \end{figure} 1108 1177 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1109 1178 1179 1180 1181 % ================================================================ 1182 % Ice sheet coupling 1183 % ================================================================ 1110 1184 \section{Ice sheet coupling} 1111 1185 \label{sec:SBC_iscpl} 1112 1186 %------------------------------------------namsbc_iscpl---------------------------------------------------- 1113 1187 1114 \nlst{namsbc_iscpl} 1188 \begin{listing} 1189 \nlst{namsbc_iscpl} 1190 \caption{\forcode{&namsbc_iscpl}} 1191 \label{lst:namsbc_iscpl} 1192 \end{listing} 1115 1193 %-------------------------------------------------------------------------------------------------------- 1194 1116 1195 Ice sheet/ocean coupling is done through file exchange at the restart step. 1117 1196 At each restart step: 1197 1118 1198 \begin{description} 1119 1199 \item[Step 1]: the ice sheet model send a new bathymetry and ice shelf draft netcdf file. 1120 1200 \item[Step 2]: a new domcfg.nc file is built using the DOMAINcfg tools. 1121 \item[Step 3]: NEMOrun for a specific period and output the average melt rate over the period.1201 \item[Step 3]: \NEMO\ run for a specific period and output the average melt rate over the period. 1122 1202 \item[Step 4]: the ice sheet model run using the melt rate outputed in step 4. 1123 1203 \item[Step 5]: go back to 1. 1124 1204 \end{description} 1125 1205 1126 If \np{ln\_iscpl}\forcode{ =.true.}, the isf draft is assume to be different at each restart step with1206 If \np{ln\_iscpl}\forcode{=.true.}, the isf draft is assume to be different at each restart step with 1127 1207 potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics. 1128 1208 The wetting and drying scheme applied on the restart is very simple and described below for the 6 different possible cases: 1209 1129 1210 \begin{description} 1130 1211 \item[Thin a cell down]: … … 1136 1217 mask, T/S, U/V and ssh are set to 0. 1137 1218 Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1138 \item[Wet a cell]: 1219 \item[Wet a cell]: 1139 1220 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. 1221 If no neighbours, T/S is extrapolated from old top cell value. 1141 1222 If no neighbours along i,j and k (both previous test failed), T/S/U/V/ssh and mask are set to 0. 1142 1223 \item[Dry a column]: … … 1155 1236 The default number is set up for the MISOMIP idealised experiments. 1156 1237 This coupling procedure is able to take into account grounding line and calving front migration. 1157 However, it is a non-conservative processe. 1238 However, it is a non-conservative processe. 1158 1239 This could lead to a trend in heat/salt content and volume.\\ 1159 1240 1160 1241 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.}.1242 a simple conservation scheme is available with \np{ln\_hsb}\forcode{=.true.}. 1162 1243 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. 1244 A correction increment is computed and apply each time step during the next \np{rn\_fiscpl} time steps. 1164 1245 For safety, it is advised to set \np{rn\_fiscpl} equal to the coupling period (smallest increment possible). 1165 1246 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 1247 1167 % 1248 1249 1168 1250 % ================================================================ 1169 1251 % Handling of icebergs 1170 1252 % ================================================================ 1171 1253 \section{Handling of icebergs (ICB)} 1172 \label{sec: ICB_icebergs}1254 \label{sec:SBC_ICB_icebergs} 1173 1255 %------------------------------------------namberg---------------------------------------------------- 1174 1256 1175 \nlst{namberg} 1257 \begin{listing} 1258 \nlst{namberg} 1259 \caption{\forcode{&namberg}} 1260 \label{lst:namberg} 1261 \end{listing} 1176 1262 %------------------------------------------------------------------------------------------------------------- 1177 1263 1178 Icebergs are modelled as lagrangian particles in NEMO\citep{marsh.ivchenko.ea_GMD15}.1264 Icebergs are modelled as lagrangian particles in \NEMO\ \citep{marsh.ivchenko.ea_GMD15}. 1179 1265 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).1266 (Note that the authors kindly provided a copy of their code to act as a basis for implementation in \NEMO). 1181 1267 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}.1268 described in the \nam{berg} namelist: \np{rn\_initial\_mass} and \np{rn\_initial\_thickness}. 1183 1269 Each class has an associated scaling (\np{rn\_mass\_scaling}), 1184 1270 which is an integer representing how many icebergs of this class are being described as one lagrangian point 1185 1271 (this reduces the numerical problem of tracking every single iceberg). 1186 They are enabled by setting \np{ln\_icebergs}\forcode{ =.true.}.1272 They are enabled by setting \np{ln\_icebergs}\forcode{=.true.}. 1187 1273 1188 1274 Two initialisation schemes are possible. … … 1195 1281 \np{nn\_test\_icebergs} is defined by four numbers in \np{nn\_test\_box} representing the corners of 1196 1282 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.1283 \item[\np{nn\_test\_icebergs}\forcode{=-1}] 1284 In this scheme, the model reads a calving file supplied in the \np{sn\_icb} parameter. 1199 1285 This should be a file with a field on the configuration grid (typically ORCA) 1200 1286 representing ice accumulation rate at each model point. … … 1204 1290 At each time step, a test is performed to see if there is enough ice mass to 1205 1291 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).1292 Note that this is the initial mass multiplied by the number each particle represents (\ie\ the scaling). 1207 1293 If there is enough ice, a new iceberg is spawned and the total available ice reduced accordingly. 1208 1294 \end{description} … … 1213 1299 or (if \np{rn\_bits\_erosion\_fraction}~$>$~0) into melt and additionally small ice bits 1214 1300 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.1301 Melt water (and other variables on the configuration grid) are written into the main \NEMO\ model output files. 1216 1302 1217 1303 Extensive diagnostics can be produced. … … 1234 1320 since its trajectory data may be spread across multiple files. 1235 1321 1236 % ------------------------------------------------------------------------------------------------------------- 1322 1323 1324 % ============================================================================================================= 1237 1325 % 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})} 1326 % ============================================================================================================= 1327 \section[Interactions with waves (\textit{sbcwave.F90}, \forcode{ln_wave})]{Interactions with waves (\protect\mdl{sbcwave}, \protect\np{ln\_wave})} 1241 1328 \label{sec:SBC_wave} 1242 1329 %------------------------------------------namsbc_wave-------------------------------------------------------- 1243 1330 1244 \nlst{namsbc_wave} 1331 \begin{listing} 1332 \nlst{namsbc_wave} 1333 \caption{\forcode{&namsbc_wave}} 1334 \label{lst:namsbc_wave} 1335 \end{listing} 1245 1336 %------------------------------------------------------------------------------------------------------------- 1246 1337 1247 Ocean waves represent the interface between the ocean and the atmosphere, so NEMO is extended to incorporate1248 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 1338 Ocean waves represent the interface between the ocean and the atmosphere, so \NEMO\ is extended to incorporate 1339 physical processes related to ocean surface waves, namely the surface stress modified by growth and 1340 dissipation of the oceanic wave field, the Stokes-Coriolis force and the Stokes drift impact on mass and 1341 tracer advection; moreover the neutral surface drag coefficient from a wave model can be used to evaluate 1251 1342 the wind stress. 1252 1343 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.1344 Physical processes related to ocean surface waves can be accounted by setting the logical variable 1345 \np{ln\_wave}\forcode{=.true.} in \nam{sbc} namelist. In addition, specific flags accounting for 1346 different processes should be activated as explained in the following sections. 1256 1347 1257 1348 Wave fields can be provided either in forced or coupled mode: 1258 1349 \begin{description} 1259 \item[forced mode]: wave fields should be defined through the \n gn{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.1350 \item[forced mode]: wave fields should be defined through the \nam{sbc\_wave} namelist 1351 for external data names, locations, frequency, interpolation and all the miscellanous options allowed by 1352 Input Data generic Interface (see \autoref{sec:SBC_input}). 1353 \item[coupled mode]: \NEMO\ and an external wave model can be coupled by setting \np{ln\_cpl} \forcode{= .true.} 1354 in \nam{sbc} namelist and filling the \nam{sbc\_cpl} namelist. 1264 1355 \end{description} 1265 1356 1266 1357 1267 % ================================================================1358 % ---------------------------------------------------------------- 1268 1359 % Neutral drag coefficient from wave model (ln_cdgw) 1269 1360 1270 % ================================================================ 1271 \subsection[Neutral drag coefficient from wave model (\texttt{ln\_cdgw})] 1272 {Neutral drag coefficient from wave model (\protect\np{ln\_cdgw})} 1361 % ---------------------------------------------------------------- 1362 \subsection[Neutral drag coefficient from wave model (\forcode{ln_cdgw})]{Neutral drag coefficient from wave model (\protect\np{ln\_cdgw})} 1273 1363 \label{subsec:SBC_wave_cdgw} 1274 1364 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 \n gn{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 % ================================================================1365 The neutral surface drag coefficient provided from an external data source (\ie\ a wave model), 1366 can be used by setting the logical variable \np{ln\_cdgw} \forcode{= .true.} in \nam{sbc} namelist. 1367 Then using the routine \rou{sbcblk\_algo\_ncar} and starting from the neutral drag coefficent provided, 1368 the drag coefficient is computed according to the stable/unstable conditions of the 1369 air-sea interface following \citet{large.yeager_rpt04}. 1370 1371 1372 % ---------------------------------------------------------------- 1283 1373 % 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})} 1374 % ---------------------------------------------------------------- 1375 \subsection[3D Stokes Drift (\forcode{ln_sdw}, \forcode{nn_sdrift})]{3D Stokes Drift (\protect\np{ln\_sdw, nn\_sdrift})} 1287 1376 \label{subsec:SBC_wave_sdw} 1288 1377 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: 1378 The Stokes drift is a wave driven mechanism of mass and momentum transport \citep{stokes_ibk09}. 1379 It is defined as the difference between the average velocity of a fluid parcel (Lagrangian velocity) 1380 and the current measured at a fixed point (Eulerian velocity). 1381 As waves travel, the water particles that make up the waves travel in orbital motions but 1382 without a closed path. Their movement is enhanced at the top of the orbit and slowed slightly 1383 at the bottom, so the result is a net forward motion of water particles, referred to as the Stokes drift. 1384 An accurate evaluation of the Stokes drift and the inclusion of related processes may lead to improved 1385 representation of surface physics in ocean general circulation models. %GS: reference needed 1386 The Stokes drift velocity $\mathbf{U}_{st}$ in deep water can be computed from the wave spectrum and may be written as: 1298 1387 1299 1388 \[ 1300 % \label{eq: sbc_wave_sdw}1389 % \label{eq:SBC_wave_sdw} 1301 1390 \mathbf{U}_{st} = \frac{16{\pi^3}} {g} 1302 1391 \int_0^\infty \int_{-\pi}^{\pi} (cos{\theta},sin{\theta}) {f^3} … … 1304 1393 \] 1305 1394 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: 1395 where: ${\theta}$ is the wave direction, $f$ is the wave intrinsic frequency, 1396 $\mathrm{S}($f$,\theta)$ is the 2D frequency-direction spectrum, 1397 $k$ is the mean wavenumber defined as: 1309 1398 $k=\frac{2\pi}{\lambda}$ (being $\lambda$ the wavelength). \\ 1310 1399 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. 1400 In order to evaluate the Stokes drift in a realistic ocean wave field, the wave spectral shape is required 1401 and its computation quickly becomes expensive as the 2D spectrum must be integrated for each vertical level. 1313 1402 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 drift 1316 $\mathbf{U}_{st |_{z=0}}$ 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 1403 Three possible parameterizations for the calculation for the approximate Stokes drift velocity profile 1404 are included in the code through the \np{nn\_sdrift} parameter once provided the surface Stokes drift 1405 $\mathbf{U}_{st |_{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra 1406 and makes possible the estimation of the surface Stokes drift for random directional waves in 1318 1407 realistic wave conditions: 1319 1408 1320 1409 \begin{description} 1321 \item[\np{nn\_sdrift} = 0]: exponential integral profile parameterization proposed by 1410 \item[\np{nn\_sdrift} = 0]: exponential integral profile parameterization proposed by 1322 1411 \citet{breivik.janssen.ea_JPO14}: 1323 1412 1324 1413 \[ 1325 % \label{eq: sbc_wave_sdw_0a}1326 \mathbf{U}_{st} \cong \mathbf{U}_{st |_{z=0}} \frac{\mathrm{e}^{-2k_ez}} {1-8k_ez} 1414 % \label{eq:SBC_wave_sdw_0a} 1415 \mathbf{U}_{st} \cong \mathbf{U}_{st |_{z=0}} \frac{\mathrm{e}^{-2k_ez}} {1-8k_ez} 1327 1416 \] 1328 1417 … … 1330 1419 1331 1420 \[ 1332 % \label{eq: sbc_wave_sdw_0b}1421 % \label{eq:SBC_wave_sdw_0b} 1333 1422 k_e = \frac{|\mathbf{U}_{\left.st\right|_{z=0}}|} {|T_{st}|} 1334 1423 \quad \text{and }\ 1335 T_{st} = \frac{1}{16} \bar{\omega} H_s^2 1424 T_{st} = \frac{1}{16} \bar{\omega} H_s^2 1336 1425 \] 1337 1426 1338 1427 where $H_s$ is the significant wave height and $\omega$ is the wave frequency. 1339 1428 1340 \item[\np{nn\_sdrift} = 1]: velocity profile based on the Phillips spectrum which is considered to be a 1341 reasonable estimate of the part of the spectrum most contributing to the Stokes drift velocity near the surface1429 \item[\np{nn\_sdrift} = 1]: velocity profile based on the Phillips spectrum which is considered to be a 1430 reasonable estimate of the part of the spectrum mostly contributing to the Stokes drift velocity near the surface 1342 1431 \citep{breivik.bidlot.ea_OM16}: 1343 1432 1344 1433 \[ 1345 % \label{eq: sbc_wave_sdw_1}1434 % \label{eq:SBC_wave_sdw_1} 1346 1435 \mathbf{U}_{st} \cong \mathbf{U}_{st |_{z=0}} \Big[exp(2k_pz)-\beta \sqrt{-2 \pi k_pz} 1347 1436 \textit{ erf } \Big(\sqrt{-2 k_pz}\Big)\Big] … … 1350 1439 where $erf$ is the complementary error function and $k_p$ is the peak wavenumber. 1351 1440 1352 \item[\np{nn\_sdrift} = 2]: velocity profile based on the Phillips spectrum as for \np{nn\_sdrift} = 1 1441 \item[\np{nn\_sdrift} = 2]: velocity profile based on the Phillips spectrum as for \np{nn\_sdrift} = 1 1353 1442 but using the wave frequency from a wave model. 1354 1443 1355 1444 \end{description} 1356 1445 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: 1446 The Stokes drift enters the wave-averaged momentum equation, as well as the tracer advection equations 1447 and its effect on the evolution of the sea-surface height ${\eta}$ is considered as follows: 1359 1448 1360 1449 \[ 1361 % \label{eq: sbc_wave_eta_sdw}1450 % \label{eq:SBC_wave_eta_sdw} 1362 1451 \frac{\partial{\eta}}{\partial{t}} = 1363 1452 -\nabla_h \int_{-H}^{\eta} (\mathbf{U} + \mathbf{U}_{st}) dz 1364 1453 \] 1365 1454 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: 1455 The tracer advection equation is also modified in order for Eulerian ocean models to properly account 1456 for unresolved wave effect. The divergence of the wave tracer flux equals the mean tracer advection 1457 that is induced by the three-dimensional Stokes velocity. 1458 The advective equation for a tracer $c$ combining the effects of the mean current and sea surface waves 1459 can be formulated as follows: 1371 1460 1372 1461 \[ 1373 % \label{eq: sbc_wave_tra_sdw}1462 % \label{eq:SBC_wave_tra_sdw} 1374 1463 \frac{\partial{c}}{\partial{t}} = 1375 1464 - (\mathbf{U} + \mathbf{U}_{st}) \cdot \nabla{c} … … 1377 1466 1378 1467 1379 % ================================================================1468 % ---------------------------------------------------------------- 1380 1469 % Stokes-Coriolis term (ln_stcor) 1381 % ================================================================ 1382 \subsection[Stokes-Coriolis term (\texttt{ln\_stcor})] 1383 {Stokes-Coriolis term (\protect\np{ln\_stcor})} 1470 % ---------------------------------------------------------------- 1471 \subsection[Stokes-Coriolis term (\forcode{ln_stcor})]{Stokes-Coriolis term (\protect\np{ln\_stcor})} 1384 1472 \label{subsec:SBC_wave_stcor} 1385 1473 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 % ================================================================1474 In a rotating ocean, waves exert a wave-induced stress on the mean ocean circulation which results 1475 in a force equal to $\mathbf{U}_{st}$×$f$, where $f$ is the Coriolis parameter. 1476 This additional force may have impact on the Ekman turning of the surface current. 1477 In order to include this term, once evaluated the Stokes drift (using one of the 3 possible 1478 approximations described in \autoref{subsec:SBC_wave_sdw}), 1479 \np{ln\_stcor}\forcode{=.true.} has to be set. 1480 1481 1482 % ---------------------------------------------------------------- 1395 1483 % 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})} 1484 % ---------------------------------------------------------------- 1485 \subsection[Wave modified stress (\forcode{ln_tauwoc} \& \forcode{ln_tauw})]{Wave modified sress (\protect\np{ln\_tauwoc, ln\_tauw})} 1399 1486 \label{subsec:SBC_wave_tauw} 1400 1487 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: 1488 The surface stress felt by the ocean is the atmospheric stress minus the net stress going 1489 into the waves \citep{janssen.breivik.ea_rpt13}. Therefore, when waves are growing, momentum and energy is spent and is not 1490 available for forcing the mean circulation, while in the opposite case of a decaying sea 1491 state, more momentum is available for forcing the ocean. 1492 Only when the sea state is in equilibrium, the ocean is forced by the atmospheric stress, 1493 but in practice, an equilibrium sea state is a fairly rare event. 1494 So the atmospheric stress felt by the ocean circulation $\tau_{oc,a}$ can be expressed as: 1408 1495 1409 1496 \[ 1410 % \label{eq: sbc_wave_tauoc}1497 % \label{eq:SBC_wave_tauoc} 1411 1498 \tau_{oc,a} = \tau_a - \tau_w 1412 1499 \] … … 1416 1503 1417 1504 \[ 1418 % \label{eq: sbc_wave_tauw}1505 % \label{eq:SBC_wave_tauw} 1419 1506 \tau_w = \rho g \int {\frac{dk}{c_p} (S_{in}+S_{nl}+S_{diss})} 1420 1507 \] 1421 1508 1422 1509 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 1510 $S_{in}$, $S_{nl}$ and $S_{diss}$ are three source terms that represent 1511 the physics of ocean waves. The first one, $S_{in}$, describes the generation 1512 of ocean waves by wind and therefore represents the momentum and energy transfer 1513 from air to ocean waves; the second term $S_{nl}$ denotes 1514 the nonlinear transfer by resonant four-wave interactions; while the third term $S_{diss}$ 1515 describes the dissipation of waves by processes such as white-capping, large scale breaking 1429 1516 eddy-induced damping. 1430 1517 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.}. 1518 The wave stress derived from an external wave model can be provided either through the normalized 1519 wave stress into the ocean by setting \np{ln\_tauwoc}\forcode{=.true.}, or through the zonal and 1520 meridional stress components by setting \np{ln\_tauw}\forcode{=.true.}. 1521 1434 1522 1435 1523 … … 1440 1528 \label{sec:SBC_misc} 1441 1529 1530 1442 1531 % ------------------------------------------------------------------------------------------------------------- 1443 1532 % Diurnal cycle 1444 1533 % ------------------------------------------------------------------------------------------------------------- 1445 \subsection[Diurnal cycle (\textit{sbcdcy.F90})] 1446 {Diurnal cycle (\protect\mdl{sbcdcy})} 1534 \subsection[Diurnal cycle (\textit{sbcdcy.F90})]{Diurnal cycle (\protect\mdl{sbcdcy})} 1447 1535 \label{subsec:SBC_dcy} 1448 %------------------------------------------namsbc _rnf----------------------------------------------------1536 %------------------------------------------namsbc------------------------------------------------------------- 1449 1537 % 1450 \nlst{namsbc} 1538 1451 1539 %------------------------------------------------------------------------------------------------------------- 1452 1540 1453 1541 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1454 1542 \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} 1543 \centering 1544 \includegraphics[width=0.66\textwidth]{Fig_SBC_diurnal} 1545 \caption[Reconstruction of the diurnal cycle variation of short wave flux]{ 1546 Example of reconstruction of the diurnal cycle variation of short wave flux from 1547 daily mean values. 1548 The reconstructed diurnal cycle (black line) is chosen as 1549 the mean value of the analytical cycle (blue line) over a time step, 1550 not as the mid time step value of the analytically cycle (red square). 1551 From \citet{bernie.guilyardi.ea_CD07}.} 1552 \label{fig:SBC_diurnal} 1466 1553 \end{figure} 1467 1554 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1468 1555 1469 1556 \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}. 1557 %Unfortunately high frequency forcing fields are rare, not to say inexistent. GS: not true anymore ! 1558 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 1559 Furthermore, only the knowledge of daily mean value of SWF is needed, 1474 1560 as higher frequency variations can be reconstructed from them, 1475 1561 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.}).1562 The \cite{bernie.guilyardi.ea_CD07} reconstruction algorithm is available in \NEMO\ by 1563 setting \np{ln\_dm2dc}\forcode{=.true.} (a \textit{\nam{sbc}} namelist variable) when 1564 using a bulk formulation (\np{ln\_blk}\forcode{=.true.}) or 1565 the flux formulation (\np{ln\_flx}\forcode{=.true.}). 1480 1566 The reconstruction is performed in the \mdl{sbcdcy} module. 1481 1567 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 at1568 The algorithm preserves the daily mean incoming SWF as the reconstructed SWF at 1483 1569 a given time step is the mean value of the analytical cycle over this time step (\autoref{fig:SBC_diurnal}). 1484 1570 The use of diurnal cycle reconstruction requires the input SWF to be daily 1485 (\ie a frequency of 24and 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,1571 (\ie\ a frequency of 24 hours and a time interpolation set to true in \np{sn\_qsr} namelist parameter). 1572 Furthermore, it is recommended to have a least 8 surface module time steps per day, 1487 1573 that is $\rdt \ nn\_fsbc < 10,800~s = 3~h$. 1488 1574 An example of recontructed SWF is given in \autoref{fig:SBC_dcy} for a 12 reconstructed diurnal cycle, … … 1491 1577 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1492 1578 \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} 1579 \centering 1580 \includegraphics[width=0.66\textwidth]{Fig_SBC_dcy} 1581 \caption[Reconstruction of the diurnal cycle variation of short wave flux on an ORCA2 grid]{ 1582 Example of reconstruction of the diurnal cycle variation of short wave flux from 1583 daily mean values on an ORCA2 grid with a time sampling of 2~hours (from 1am to 11pm). 1584 The display is on (i,j) plane.} 1585 \label{fig:SBC_dcy} 1502 1586 \end{figure} 1503 1587 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> … … 1507 1591 an inconsistency between the scale of the vertical resolution and the forcing acting on that scale. 1508 1592 1593 1509 1594 % ------------------------------------------------------------------------------------------------------------- 1510 1595 % Rotation of vector pairs onto the model grid directions … … 1513 1598 \label{subsec:SBC_rotation} 1514 1599 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, 1600 When using a flux (\np{ln\_flx}\forcode{=.true.}) or bulk (\np{ln\_blk}\forcode{=.true.}) formulation, 1517 1601 pairs of vector components can be rotated from east-north directions onto the local grid directions. 1518 1602 This is particularly useful when interpolation on the fly is used since here any vectors are likely to 1519 1603 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". 1604 To activate this option, a non-empty string is supplied in the rotation pair column of the relevant namelist. 1605 The eastward component must start with "U" and the northward component with "V". 1522 1606 The remaining characters in the strings are used to identify which pair of components go together. 1523 1607 So for example, strings "U1" and "V1" next to "utau" and "vtau" would pair the wind stress components together and … … 1527 1611 The rot\_rep routine from the \mdl{geo2ocean} module is used to perform the rotation. 1528 1612 1613 1529 1614 % ------------------------------------------------------------------------------------------------------------- 1530 1615 % Surface restoring to observed SST and/or SSS 1531 1616 % ------------------------------------------------------------------------------------------------------------- 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})} 1617 \subsection[Surface restoring to observed SST and/or SSS (\textit{sbcssr.F90})]{Surface restoring to observed SST and/or SSS (\protect\mdl{sbcssr})} 1534 1618 \label{subsec:SBC_ssr} 1535 1619 %------------------------------------------namsbc_ssr---------------------------------------------------- 1536 1620 1537 \nlst{namsbc_ssr} 1621 \begin{listing} 1622 \nlst{namsbc_ssr} 1623 \caption{\forcode{&namsbc_ssr}} 1624 \label{lst:namsbc_ssr} 1625 \end{listing} 1538 1626 %------------------------------------------------------------------------------------------------------------- 1539 1627 1540 IOptions are defined through the \ngn{namsbc\_ssr} namelist variables.1541 On forced mode using a flux formulation (\np{ln\_flx}\forcode{ =.true.}),1628 Options are defined through the \nam{sbc\_ssr} namelist variables. 1629 On forced mode using a flux formulation (\np{ln\_flx}\forcode{=.true.}), 1542 1630 a feedback term \emph{must} be added to the surface heat flux $Q_{ns}^o$: 1543 1631 \[ 1544 % \label{eq: sbc_dmp_q}1632 % \label{eq:SBC_dmp_q} 1545 1633 Q_{ns} = Q_{ns}^o + \frac{dQ}{dT} \left( \left. T \right|_{k=1} - SST_{Obs} \right) 1546 1634 \] … … 1548 1636 $T$ is the model surface layer temperature and 1549 1637 $\frac{dQ}{dT}$ 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 $Q_o$. 1638 For a $50~m$ mixed-layer depth, this value corresponds to a relaxation time scale of two months. 1639 This term ensures that if $T$ perfectly matches the supplied SST, then $Q$ is equal to $Q_o$. 1552 1640 1553 1641 In the fresh water budget, a feedback term can also be added. … … 1555 1643 1556 1644 \begin{equation} 1557 \label{eq: sbc_dmp_emp}1645 \label{eq:SBC_dmp_emp} 1558 1646 \textit{emp} = \textit{emp}_o + \gamma_s^{-1} e_{3t} \frac{ \left(\left.S\right|_{k=1}-SSS_{Obs}\right)} 1559 1647 {\left.S\right|_{k=1}} … … 1566 1654 $\left.S\right|_{k=1}$ is the model surface layer salinity and 1567 1655 $\gamma_s$ 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} as1656 Unlike heat flux, there is no physical justification for the feedback term in \autoref{eq:SBC_dmp_emp} as 1569 1657 the atmosphere does not care about ocean surface salinity \citep{madec.delecluse_IWN97}. 1570 1658 The SSS restoring term should be viewed as a flux correction on freshwater fluxes to 1571 1659 reduce the uncertainties we have on the observed freshwater budget. 1572 1660 1661 1573 1662 % ------------------------------------------------------------------------------------------------------------- 1574 1663 % Handling of ice-covered area … … 1579 1668 The presence at the sea surface of an ice covered area modifies all the fluxes transmitted to the ocean. 1580 1669 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 \n gn{namsbc} namelist.1670 the value of the \np{nn\_ice} namelist parameter found in \nam{sbc} namelist. 1582 1671 \begin{description} 1583 \item[nn {\_}ice = 0]1672 \item[nn\_ice = 0] 1584 1673 there will never be sea-ice in the computational domain. 1585 1674 This is a typical namelist value used for tropical ocean domain. 1586 1675 The surface fluxes are simply specified for an ice-free ocean. 1587 1676 No specific things is done for sea-ice. 1588 \item[nn {\_}ice = 1]1677 \item[nn\_ice = 1] 1589 1678 sea-ice can exist in the computational domain, but no sea-ice model is used. 1590 1679 An observed ice covered area is read in a file. … … 1595 1684 This prevents deep convection to occur when trying to reach the freezing point 1596 1685 (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,1686 This manner of managing sea-ice area, just by using a IF case, 1598 1687 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]1688 It can be found in the \mdl{sbcice\_if} module. 1689 \item[nn\_ice = 2 or more] 1601 1690 A full sea ice model is used. 1602 1691 This model computes the ice-ocean fluxes, 1603 1692 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).1693 provide the surface averaged ocean fluxes. 1694 Note that the activation of a sea-ice model is done by defining a CPP key (\key{si3} or \key{cice}). 1695 The activation automatically overwrites the read value of nn\_ice to its appropriate value 1696 (\ie\ $2$ for SI3 or $3$ for CICE). 1608 1697 \end{description} 1609 1698 1610 1699 % {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})} 1700 %GS: ocean-ice (SI3) interface is not located in SBC directory anymore, so it should be included in SI3 doc 1701 1702 1703 % ------------------------------------------------------------------------------------------------------------- 1704 % CICE-ocean Interface 1705 % ------------------------------------------------------------------------------------------------------------- 1706 \subsection[Interface to CICE (\textit{sbcice\_cice.F90})]{Interface to CICE (\protect\mdl{sbcice\_cice})} 1614 1707 \label{subsec:SBC_cice} 1615 1708 1616 It is now possible to couple a regional or global NEMOconfiguration (without AGRIF)1709 It is possible to couple a regional or global \NEMO\ configuration (without AGRIF) 1617 1710 to the CICE sea-ice model by using \key{cice}. 1618 1711 The CICE code can be obtained from \href{http://oceans11.lanl.gov/trac/CICE/}{LANL} and 1619 1712 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,1713 Input grid files consistent with those used in \NEMO\ will also be needed, 1621 1714 and CICE CPP keys \textbf{ORCA\_GRID}, \textbf{CICE\_IN\_NEMO} and \textbf{coupled} should be used 1622 1715 (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}).1716 Currently, the code is only designed to work when using the NCAR forcing option for \NEMO\ %GS: still true ? 1717 (with \textit{calc\_strair}\forcode{=.true.} and \textit{calc\_Tsfc}\forcode{=.true.} in the CICE name-list), 1718 or alternatively when \NEMO\ is coupled to the HadGAM3 atmosphere model 1719 (with \textit{calc\_strair}\forcode{=.false.} and \textit{calc\_Tsfc}\forcode{=false}). 1627 1720 The code is intended to be used with \np{nn\_fsbc} set to 1 1628 1721 (although coupling ocean and ice less frequently should work, … … 1630 1723 the user should check that results are not significantly different to the standard case). 1631 1724 1632 There are two options for the technical coupling between NEMOand CICE.1725 There are two options for the technical coupling between \NEMO\ and CICE. 1633 1726 The standard version allows complete flexibility for the domain decompositions in the individual models, 1634 1727 but this is at the expense of global gather and scatter operations in the coupling which 1635 1728 become very expensive on larger numbers of processors. 1636 The alternative option (using \key{nemocice\_decomp} for both NEMOand CICE) ensures that1729 The alternative option (using \key{nemocice\_decomp} for both \NEMO\ and CICE) ensures that 1637 1730 the domain decomposition is identical in both models (provided domain parameters are set appropriately, 1638 1731 and \textit{processor\_shape~=~square-ice} and \textit{distribution\_wght~=~block} in the CICE name-list) and … … 1641 1734 there is no sea ice. 1642 1735 1643 % ------------------------------------------------------------------------------------------------------------- 1644 % Freshwater budget control1645 % -------------------------------------------------------------------------------------------------------------1646 \subsection[Freshwater budget control (\textit{sbcfwb.F90})] 1647 {Freshwater budget control (\protect\mdl{sbcfwb})}1736 1737 % ------------------------------------------------------------------------------------------------------------- 1738 % Freshwater budget control 1739 % ------------------------------------------------------------------------------------------------------------- 1740 \subsection[Freshwater budget control (\textit{sbcfwb.F90})]{Freshwater budget control (\protect\mdl{sbcfwb})} 1648 1741 \label{subsec:SBC_fwb} 1649 1742 1650 For global ocean simulation it can be useful to introduce a control of the mean sea level in order to1743 For global ocean simulation, it can be useful to introduce a control of the mean sea level in order to 1651 1744 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. 1745 In \NEMO, two way of controlling the freshwater budget are proposed: 1746 1653 1747 \begin{description} 1654 \item[\np{nn\_fwb}\forcode{ =0}]1748 \item[\np{nn\_fwb}\forcode{=0}] 1655 1749 no control at all. 1656 1750 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}] 1751 \item[\np{nn\_fwb}\forcode{=1}] 1752 global mean \textit{emp} set to zero at each model time step. 1753 %GS: comment below still relevant ? 1754 %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). 1755 \item[\np{nn\_fwb}\forcode{=2}] 1661 1756 freshwater budget is adjusted from the previous year annual mean budget which 1662 1757 is read in the \textit{EMPave\_old.dat} file. 1663 1758 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. 1759 the change in the mean sea level at January the first and saved in the \textit{EMPav.dat} file. 1665 1760 \end{description} 1666 1761 1667 1668 1669 1762 % 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. 1763 % When running ocean-ice simulations, we are not explicitly representing land processes, 1764 % such as rivers, catchment areas, snow accumulation, etc. However, to reduce model drift, 1765 % it is important to balance the hydrological cycle in ocean-ice models. 1766 % We thus need to prescribe some form of global normalization to the precipitation minus evaporation plus river runoff. 1767 % The result of the normalization should be a global integrated zero net water input to the ocean-ice system over 1768 % a chosen time scale. 1769 % How often the normalization is done is a matter of choice. In mom4p1, we choose to do so at each model time step, 1770 % so that there is always a zero net input of water to the ocean-ice system. 1771 % Others choose to normalize over an annual cycle, in which case the net imbalance over an annual cycle is used 1772 % to alter the subsequent year�s water budget in an attempt to damp the annual water imbalance. 1773 % Note that the annual budget approach may be inappropriate with interannually varying precipitation forcing. 1774 % When running ocean-ice coupled models, it is incorrect to include the water transport between the ocean 1775 % and ice models when aiming to balance the hydrological cycle. 1776 % 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, 1777 % not the water in any one sub-component. As an extreme example to illustrate the issue, 1778 % consider an ocean-ice model with zero initial sea ice. As the ocean-ice model spins up, 1779 % there should be a net accumulation of water in the growing sea ice, and thus a net loss of water from the ocean. 1780 % The total water contained in the ocean plus ice system is constant, but there is an exchange of water between 1781 % the subcomponents. This exchange should not be part of the normalization used to balance the hydrological cycle 1782 % in ocean-ice models. 1783 1690 1784 1691 1785 \biblio
Note: See TracChangeset
for help on using the changeset viewer.
