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r11338 r11435 4 4 5 5 % ================================================================ 6 % Chapter —— Surface Boundary Condition (SBC, SAS, ISF, ICB) 6 % Chapter —— Surface Boundary Condition (SBC, SAS, ISF, ICB) 7 7 % ================================================================ 8 8 \chapter{Surface Boundary Condition (SBC, SAS, ISF, ICB)} 9 9 \label{chap:SBC} 10 \ minitoc10 \chaptertoc 11 11 12 12 \newpage … … 33 33 34 34 Four different ways are available to provide the seven fields to the ocean. They are controlled by 35 namelist \n gn{namsbc} variables:35 namelist \nam{sbc} variables: 36 36 37 37 \begin{itemize} … … 46 46 a user defined formulation (\np{ln\_usr}\forcode{ = .true.}). 47 47 \end{itemize} 48 49 48 50 49 The frequency at which the forcing fields have to be updated is given by the \np{nn\_fsbc} namelist parameter. … … 88 87 a neutral drag coefficient is read from an external wave model (\np{ln\_cdgw}\forcode{ = .true.}), 89 88 \item 90 the Stokes drift from an external wave model is accounted for (\np{ln\_sdw}\forcode{ = .true.}), 91 \item 92 the choice of the Stokes drift profile parameterization (\np{nn\_sdrift}\forcode{ = 0..2}), 89 the Stokes drift from an external wave model is accounted for (\np{ln\_sdw}\forcode{ = .true.}), 90 \item 91 the choice of the Stokes drift profile parameterization (\np{nn\_sdrift}\forcode{ = 0..2}), 93 92 \item 94 93 the surface stress given to the ocean is modified by surface waves (\np{ln\_tauwoc}\forcode{ = .true.}), … … 98 97 the StokesCoriolis term is included (\np{ln\_stcor}\forcode{ = .true.}), 99 98 \item 100 the light penetration in the ocean (\np{ln\_traqsr}\forcode{ = .true.} with namelist \n gn{namtra\_qsr}),101 \item 102 the atmospheric surface pressure gradient effect on ocean and ice dynamics (\np{ln\_apr\_dyn}\forcode{ = .true.} with namelist \n gn{namsbc\_apr}),99 the light penetration in the ocean (\np{ln\_traqsr}\forcode{ = .true.} with namelist \nam{tra\_qsr}), 100 \item 101 the atmospheric surface pressure gradient effect on ocean and ice dynamics (\np{ln\_apr\_dyn}\forcode{ = .true.} with namelist \nam{sbc\_apr}), 103 102 \item 104 103 the effect of seaice pressure on the ocean (\np{ln\_ice\_embd}\forcode{ = .true.}). … … 106 105 107 106 In this chapter, we first discuss where the surface boundary conditions appear in the model equations. 108 Then we present the three ways of providing the surface boundary conditions, 109 followed by the description of the atmospheric pressure and the river runoff. 107 Then we present the three ways of providing the surface boundary conditions, 108 followed by the description of the atmospheric pressure and the river runoff. 110 109 Next, the scheme for interpolation on the fly is described. 111 110 Finally, the different options that further modify the fluxes applied to the ocean are discussed. 112 111 One of these is modification by icebergs (see \autoref{sec:ICB_icebergs}), 113 112 which act as drifting sources of fresh water. 114 Another example of modification is that due to the ice shelf melting/freezing (see \autoref{sec:SBC_isf}), 113 Another example of modification is that due to the ice shelf melting/freezing (see \autoref{sec:SBC_isf}), 115 114 which provides additional sources of fresh water. 116 115 … … 127 126 the momentum vertical mixing trend (see \autoref{eq:dynzdf_sbc} in \autoref{sec:DYN_zdf}). 128 127 As such, it has to be provided as a 2D vector interpolated onto the horizontal velocity ocean mesh, 129 \ie resolved onto the model (\textbf{i},\textbf{j}) direction at $u$ and $v$points.128 \ie\ resolved onto the model (\textbf{i},\textbf{j}) direction at $u$ and $v$points. 130 129 131 130 The surface heat flux is decomposed into two parts, a non solar and a solar heat flux, 132 131 $Q_{ns}$ and $Q_{sr}$, respectively. 133 132 The former is the non penetrative part of the heat flux 134 (\ie the sum of sensible, latent and long wave heat fluxes plus133 (\ie\ the sum of sensible, latent and long wave heat fluxes plus 135 134 the heat content of the mass exchange between the ocean and seaice). 136 135 It is applied in \mdl{trasbc} module as a surface boundary condition trend of … … 141 140 \np{ln\_traqsr}\forcode{ = .true.}. 142 141 The way the light penetrates inside the water column is generally a sum of decreasing exponentials 143 (see \autoref{subsec:TRA_qsr}). 142 (see \autoref{subsec:TRA_qsr}). 144 143 145 144 The surface freshwater budget is provided by the \textit{emp} field. … … 148 147 It affects the ocean in two different ways: 149 148 $(i)$ it changes the volume of the ocean, and therefore appears in the sea surface height equation as %GS: autoref ssh equation to be added 150 a volume flux, and 149 a volume flux, and 151 150 $(ii)$ it changes the surface temperature and salinity through the heat and salt contents of 152 151 the mass exchanged with atmosphere, seaice and ice shelves. … … 155 154 %\colorbox{yellow}{Miss: } 156 155 % 157 %A extensive description of all namsbc namelist (parameter that have to be 156 %A extensive description of all namsbc namelist (parameter that have to be 158 157 %created!) 159 158 % 160 %Especially the \np{nn\_fsbc}, the \mdl{sbc\_oce} module (fluxes + mean sst sss ssu 161 %ssv) \ie information required by flux computation or seaice159 %Especially the \np{nn\_fsbc}, the \mdl{sbc\_oce} module (fluxes + mean sst sss ssu 160 %ssv) \ie\ information required by flux computation or seaice 162 161 % 163 %\mdl{sbc\_oce} containt the definition in memory of the 7 fields (6+runoff), add 162 %\mdl{sbc\_oce} containt the definition in memory of the 7 fields (6+runoff), add 164 163 %a word on runoff: included in surface bc or add as lateral obc{\ldots}. 165 164 % 166 165 %Sbcmod manage the ``providing'' (fourniture) to the ocean the 7 fields 167 166 % 168 %Fluxes update only each nf {\_}sbc time step (namsbc) explain relation169 %between nf {\_}sbc and nf{\_}ice, do we define nf{\_}blk??? ? only one170 %nf {\_}sbc167 %Fluxes update only each nf\_sbc time step (namsbc) explain relation 168 %between nf\_sbc and nf\_ice, do we define nf\_blk??? ? only one 169 %nf\_sbc 171 170 % 172 171 %Explain here all the namlist namsbc variable{\ldots}. 173 % 172 % 174 173 % explain : use or not of surface currents 175 174 % … … 177 176 178 177 The ocean model provides, at each time step, to the surface module (\mdl{sbcmod}) 179 the surface currents, temperature and salinity. 178 the surface currents, temperature and salinity. 180 179 These variables are averaged over \np{nn\_fsbc} timestep (\autoref{tab:ssm}), and 181 180 these averaged fields are used to compute the surface fluxes at the frequency of \np{nn\_fsbc} timesteps. … … 197 196 Ocean variables provided by the ocean to the surface module (SBC). 198 197 The variable are averaged over \np{nn\_fsbc} timestep, 199 \ie the frequency of computation of surface fluxes.198 \ie\ the frequency of computation of surface fluxes. 200 199 } 201 200 \end{center} … … 203 202 % 204 203 205 %\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 pdt206 207 208 209 % ================================================================ 210 % Input Data 204 %\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 205 206 207 208 % ================================================================ 209 % Input Data 211 210 % ================================================================ 212 211 \section{Input data generic interface} … … 216 215 (2D or 3D fields, like surface forcing or ocean T and S) are specified in \NEMO. 217 216 This task is achieved by \mdl{fldread}. 218 The module is designed with four main objectives in mind: 217 The module is designed with four main objectives in mind: 219 218 \begin{enumerate} 220 219 \item … … 227 226 \item 228 227 provide a simple user interface and a rather simple developer interface by 229 limiting the number of prerequisite informations. 228 limiting the number of prerequisite informations. 230 229 \end{enumerate} 231 230 … … 238 237 and simply call \rou{fld\_read} to obtain the desired input field at the model timestep and grid points. 239 238 240 The only constraints are that the input file is a NetCDF file, the file name follows a nomenclature 239 The only constraints are that the input file is a NetCDF file, the file name follows a nomenclature 241 240 (see \autoref{subsec:SBC_fldread}), the period it cover is one year, month, week or day, and, 242 241 if onthefly interpolation is used, a file of weights must be supplied (see \autoref{subsec:SBC_iof}). … … 256 255 The structure associated with an input variable contains the following information: 257 256 \begin{forlines} 258 ! file name ! frequency (hours) ! variable ! time interp. ! clim ! 'yearly'/ ! weights ! rotation ! land/sea mask ! 257 ! file name ! frequency (hours) ! variable ! time interp. ! clim ! 'yearly'/ ! weights ! rotation ! land/sea mask ! 259 258 ! ! (if <0 months) ! name ! (logical) ! (T/F) ! 'monthly' ! filename ! pairing ! filename ! 260 259 \end{forlines} 261 where 262 \begin{description} 260 where 261 \begin{description} 263 262 \item[File name]: 264 263 the stem name of the NetCDF file to be opened. 265 264 This stem will be completed automatically by the model, with the addition of a '.nc' at its end and 266 265 by date information and possibly a prefix (when using AGRIF). 267 Tab.\autoref{tab:fldread} provides the resulting file name in all possible cases according to266 \autoref{tab:fldread} provides the resulting file name in all possible cases according to 268 267 whether it is a climatological file or not, and to the open/close frequency (see below for definition). 269 268 … … 283 282 The stem name is assumed to be 'fn'. 284 283 For weekly files, the 'LLL' corresponds to the first three letters of the first day of the week 285 (\ie 'sun','sat','fri','thu','wed','tue','mon').284 (\ie\ 'sun','sat','fri','thu','wed','tue','mon'). 286 285 The 'YYYY', 'MM' and 'DD' should be replaced by the actual year/month/day, always coded with 4 or 2 digits. 287 286 Note that (1) in mpp, if the file is split over each subdomain, the suffix '.nc' is replaced by '\_PPPP.nc', … … 291 290 \end{table} 292 291 % 293 292 294 293 295 294 \item[Record frequency]: … … 311 310 Records are assumed to be dated at the middle of the forcing period. 312 311 For example, when using a daily forcing with time interpolation, 313 linear interpolation will be performed between midday of two consecutive days. 312 linear interpolation will be performed between midday of two consecutive days. 314 313 315 314 \item[Climatological forcing]: … … 317 316 or an interannual forcing which will requires additional files if 318 317 the period covered by the simulation exceeds the one of the file. 319 See the above file naming strategy which impacts the expected name of the file to be opened. 318 See the above file naming strategy which impacts the expected name of the file to be opened. 320 319 321 320 \item[Open/close frequency]: … … 345 344 For example with \np{nn\_fsbc}\forcode{ = 3}, the surface module will be called at timesteps 1, 4, 7, etc. 346 345 The date used for the time interpolation is thus redefined to the middle of \np{nn\_fsbc} timestep period. 347 In the previous example, this leads to: 1h30'00", 4h30'00", 7h30'00", etc. \\ 346 In the previous example, this leads to: 1h30'00", 4h30'00", 7h30'00", etc. \\ 348 347 (2) For code readablility and maintenance issues, we don't take into account the NetCDF input file calendar. 349 348 The calendar associated with the forcing field is build according to the information provided by … … 353 352 (3) If a time interpolation is requested, the code will pick up the needed data in the previous (next) file when 354 353 interpolating data with the first (last) record of the open/close period. 355 For example, if the input file specifications are ''yearly, containing daily data to be interpolated in time'', 354 For example, if the input file specifications are ''yearly, containing daily data to be interpolated in time'', 356 355 the values given by the code between 00h00'00" and 11h59'59" on Jan 1st will be interpolated values between 357 356 Dec 31st 12h00'00" and Jan 1st 12h00'00". … … 365 364 we do accept that the file related to year Y1 is not existing. 366 365 The value of Jan 1st will be used as the missing one for Dec 31st of year Y1. 367 If the file of year Y1 exists, the code will read its last record. 366 If the file of year Y1 exists, the code will read its last record. 368 367 Therefore, this file can contain only one record corresponding to Dec 31st, 369 368 a useful feature for user considering that it is too heavy to manipulate the complete file for year Y1. … … 488 487 \label{subsec:SBC_iof_lim} 489 488 490 \begin{enumerate} 489 \begin{enumerate} 491 490 \item 492 491 The case where input data grids are not logically rectangular (irregular grid case) has not been tested. … … 524 523 525 524 In some circumstances, it may be useful to avoid calculating the 3D temperature, 526 salinity and velocity fields and simply read them in from a previous run or receive them from OASIS. 525 salinity and velocity fields and simply read them in from a previous run or receive them from OASIS. 527 526 For example: 528 527 … … 542 541 543 542 The Standalone Surface scheme provides this capacity. 544 Its options are defined through the \n gn{namsbc\_sas} namelist variables.543 Its options are defined through the \nam{sbc\_sas} namelist variables. 545 544 A new copy of the model has to be compiled with a configuration based on ORCA2\_SAS\_LIM. 546 However, no namelist parameters need be changed from the settings of the previous run (except perhaps nn {\_}date0).545 However, no namelist parameters need be changed from the settings of the previous run (except perhaps nn\_date0). 547 546 In this configuration, a few routines in the standard model are overriden by new versions. 548 547 Routines replaced are: … … 560 559 This has been cut down and now only calculates surface forcing and the ice model required. 561 560 New surface modules that can function when only the surface level of the ocean state is defined can also be added 562 (\eg icebergs).561 (\eg\ icebergs). 563 562 \item 564 563 \mdl{daymod}: … … 566 565 so calls to restart functions have been removed. 567 566 This also means that the calendar cannot be controlled by time in a restart file, 568 so the user must check that nn {\_}date0 in the model namelist is correct for his or her purposes.567 so the user must check that nn\_date0 in the model namelist is correct for his or her purposes. 569 568 \item 570 569 \mdl{stpctl}: … … 584 583 This module initialises the input files needed for reading temperature, salinity and 585 584 velocity arrays at the surface. 586 These filenames are supplied in namelist namsbc {\_}sas.585 These filenames are supplied in namelist namsbc\_sas. 587 586 Unfortunately, because of limitations with the \mdl{iom} module, 588 587 the full 3D fields from the mean files have to be read in and interpolated in time, … … 592 591 593 592 594 The user can also choose in the \n gn{namsbc\_sas} namelist to read the mean (nn\_fsbc timestep) fraction of solar net radiation absorbed in the 1st T level using593 The user can also choose in the \nam{sbc\_sas} namelist to read the mean (nn\_fsbc timestep) fraction of solar net radiation absorbed in the 1st T level using 595 594 (\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. 596 595 … … 598 597 599 598 % ================================================================ 600 % Flux formulation 599 % Flux formulation 601 600 % ================================================================ 602 601 \section[Flux formulation (\textit{sbcflx.F90})] … … 605 604 %namsbc_flx 606 605 607 \nlst{namsbc_flx} 606 \nlst{namsbc_flx} 608 607 % 609 608 610 609 In the flux formulation (\np{ln\_flx}\forcode{ = .true.}), 611 610 the surface boundary condition fields are directly read from input files. 612 The user has to define in the namelist \n gn{namsbc{\_}flx} the name of the file,611 The user has to define in the namelist \nam{sbc\_flx} the name of the file, 613 612 the name of the variable read in the file, the time frequency at which it is given (in hours), 614 613 and a logical setting whether a time interpolation to the model time step is required for this field. … … 631 630 % 632 631 633 In the bulk formulation, the surface boundary condition fields are computed with bulk formulae using atmospheric fields 632 In the bulk formulation, the surface boundary condition fields are computed with bulk formulae using atmospheric fields 634 633 and ocean (and seaice) variables averaged over \np{nn\_fsbc} timestep. 635 634 … … 637 636 In forced mode, when a seaice model is used, a specific bulk formulation is used. 638 637 Therefore, different bulk formulae are used for the turbulent fluxes computation 639 over the ocean and over seaice surface. 640 For the ocean, four bulk formulations are available thanks to the \href{https://brodeau.github.io/aerobulk/}{Aerobulk} package (\citet{brodeau.barnier.ea_JPO16}): 638 over the ocean and over seaice surface. 639 For the ocean, four bulk formulations are available thanks to the \href{https://brodeau.github.io/aerobulk/}{Aerobulk} package (\citet{brodeau.barnier.ea_JPO16}): 641 640 the NCAR (formerly named CORE), COARE 3.0, COARE 3.5 and ECMWF bulk formulae. 642 641 The choice is made by setting to true one of the following namelist variable: … … 645 644 a constant transfer coefficient (1.4e3; default value), \citet{lupkes.gryanik.ea_JGR12} (\np{ln\_Cd\_L12}), and \citet{lupkes.gryanik_JGR15} (\np{ln\_Cd\_L15}) parameterizations 646 645 647 Common options are defined through the \n gn{namsbc\_blk} namelist variables.646 Common options are defined through the \nam{sbc\_blk} namelist variables. 648 647 The required 9 input fields are: 649 648 … … 675 674 The \np{sn\_wndi}, \np{sn\_wndj}, \np{sn\_qsr}, \np{sn\_qlw}, \np{sn\_tair}, \np{sn\_humi}, \np{sn\_prec}, 676 675 \np{sn\_snow}, \np{sn\_tdif} parameters describe the fields and the way they have to be used 677 (spatial and temporal interpolations). 676 (spatial and temporal interpolations). 678 677 679 678 \np{cn\_dir} is the directory of location of bulk files … … 682 681 \np{rn\_zu}: is the height of wind measurements (m) 683 682 684 Three multiplicative factors are available: 683 Three multiplicative factors are available: 685 684 \np{rn\_pfac} and \np{rn\_efac} allow to adjust (if necessary) the global freshwater budget by 686 685 increasing/reducing the precipitations (total and snow) and or evaporation, respectively. … … 690 689 691 690 As for the flux formulation, information about the input data required by the model is provided in 692 the namsbc\_blk namelist (see \autoref{subsec:SBC_fldread}). 691 the namsbc\_blk namelist (see \autoref{subsec:SBC_fldread}). 693 692 694 693 … … 696 695 % OceanAtmosphere Bulk formulae 697 696 %  698 \subsection{OceanAtmosphere Bulk formulae} 699 %\subsection[OceanAtmosphere Bulk formulae (\textit{sbcblk_algo\{\_ncar,\_coare,\_coare3p5,\_ecmwf}.F90})] 697 \subsection[OceanAtmosphere Bulk formulae (\textit{sbcblk\_algo\_coare.F90, sbcblk\_algo\_coare3p5.F90, 698 sbcblk\_algo\_ecmwf.F90, sbcblk\_algo\_ncar.F90})] 699 {OceanAtmosphere Bulk formulae (\mdl{sbcblk\_algo\_coare}, \mdl{sbcblk\_algo\_coare3p5}, 700 \mdl{sbcblk\_algo\_ecmwf}, \mdl{sbcblk\_algo\_ncar})} 700 701 \label{subsec:SBC_blk_ocean} 701 702 702 703 Four different bulk algorithms are available to compute surface turbulent momentum and heat fluxes over the ocean. 703 COARE 3.0, COARE 3.5 and ECMWF schemes mainly differ by their roughness lenghts computation and consequently 704 COARE 3.0, COARE 3.5 and ECMWF schemes mainly differ by their roughness lenghts computation and consequently 704 705 their neutral transfer coefficients relationships with neutral wind. 705 706 \begin{itemize} … … 715 716 This is the socalled DRAKKAR Forcing Set (DFS) \citep{brodeau.barnier.ea_OM10}. 716 717 \item 717 COARE 3.0 (\np{ln\_COARE\_3p0}\forcode{ = .true.}): 718 COARE 3.0 (\np{ln\_COARE\_3p0}\forcode{ = .true.}): 718 719 See \citet{fairall.bradley.ea_JC03} for more details 719 720 \item 720 COARE 3.5 (\np{ln\_COARE\_3p5}\forcode{ = .true.}): 721 COARE 3.5 (\np{ln\_COARE\_3p5}\forcode{ = .true.}): 721 722 See \citet{edson.jampana.ea_JPO13} for more details 722 723 \item 723 ECMWF (\np{ln\_ECMWF}\forcode{ = .true.}): 724 ECMWF (\np{ln\_ECMWF}\forcode{ = .true.}): 724 725 Based on \href{https://www.ecmwf.int/node/9221}{IFS (Cy31)} implementation and documentation. 725 726 Surface roughness lengths needed for the Obukhov length are computed following \citet{beljaars_QJRMS95}. 726 727 \end{itemize} 727 728 728 729 729 %  730 730 % IceAtmosphere Bulk formulae 731 731 %  732 \subsection{ IceAtmosphere Bulk formulae}732 \subsection{IceAtmosphere Bulk formulae} 733 733 \label{subsec:SBC_blk_ice} 734 734 … … 742 742 \citet{lupkes.gryanik.ea_JGR12} (\np{ln\_Cd\_L12}\forcode{ = .true.}): 743 743 This scheme adds a dependency on edges at leads, melt ponds and flows 744 of the constant neutral airice drag. After some approximations, 744 of the constant neutral airice drag. After some approximations, 745 745 this can be resumed to a dependency on ice concentration (A). 746 746 This drag coefficient has a parabolic shape (as a function of ice concentration) … … 749 749 \item 750 750 \citet{lupkes.gryanik_JGR15} (\np{ln\_Cd\_L15}\forcode{ = .true.}): 751 Alternative turbulent transfer coefficients formulation between seaice 752 and atmosphere with distinct momentum and heat coefficients depending 751 Alternative turbulent transfer coefficients formulation between seaice 752 and atmosphere with distinct momentum and heat coefficients depending 753 753 on seaice concentration and atmospheric stability (no meltponds effect for now). 754 754 The parameterization is adapted from ECHAM6 atmospheric model. … … 768 768 %namsbc_cpl 769 769 770 \nlst{namsbc_cpl} 770 \nlst{namsbc_cpl} 771 771 % 772 772 … … 779 779 It is currently interfaced with OASIS3MCT versions 1 to 4 (\key{oasis3}). 780 780 An additional specific CPP key (\key{oa3mct\_v1v2}) is needed for OASIS3MCT versions 1 and 2. 781 It has been successfully used to interface \NEMO to most of the European atmospheric GCM781 It has been successfully used to interface \NEMO\ to most of the European atmospheric GCM 782 782 (ARPEGE, ECHAM, ECMWF, HadAM, HadGAM, LMDz), as well as to \href{http://wrfmodel.org/}{WRF} 783 783 (Weather Research and Forecasting Model). 784 784 785 When PISCES biogeochemical model (\key{top}) is also used in the coupled system, 785 When PISCES biogeochemical model (\key{top}) is also used in the coupled system, 786 786 the whole carbon cycle is computed. 787 787 In this case, CO$_2$ fluxes will be exchanged between the atmosphere and the iceocean system 788 (and need to be activated in \n gn{namsbc{\_}cpl} ).788 (and need to be activated in \nam{sbc\_cpl} ). 789 789 790 790 The namelist above allows control of various aspects of the coupling fields (particularly for vectors) and 791 791 now allows for any coupling fields to have multiple sea ice categories (as required by LIM3 and CICE). 792 When indicating a multicategory coupling field in \n gn{namsbc{\_}cpl}, the number of categories will be determined by792 When indicating a multicategory coupling field in \nam{sbc\_cpl}, the number of categories will be determined by 793 793 the number used in the sea ice model. 794 794 In some limited cases, it may be possible to specify single category coupling fields even when … … 807 807 %namsbc_apr 808 808 809 \nlst{namsbc_apr} 809 \nlst{namsbc_apr} 810 810 % 811 811 812 812 The optional atmospheric pressure can be used to force ocean and ice dynamics 813 (\np{ln\_apr\_dyn}\forcode{ = .true.}, \n gn{namsbc} namelist).814 The input atmospheric forcing defined via \np{sn\_apr} structure (\n gn{namsbc\_apr} namelist)813 (\np{ln\_apr\_dyn}\forcode{ = .true.}, \nam{sbc} namelist). 814 The input atmospheric forcing defined via \np{sn\_apr} structure (\nam{sbc\_apr} namelist) 815 815 can be interpolated in time to the model time step, and even in space when the interpolation onthefly is used. 816 816 When used to force the dynamics, the atmospheric pressure is further transformed into … … 823 823 A value of $101,000~N/m^2$ is used unless \np{ln\_ref\_apr} is set to true. 824 824 In this case, $P_o$ is set to the value of $P_{atm}$ averaged over the ocean domain, 825 \ie the mean value of $\eta_{ib}$ is kept to zero at all time steps.825 \ie\ the mean value of $\eta_{ib}$ is kept to zero at all time steps. 826 826 827 827 The gradient of $\eta_{ib}$ is added to the RHS of the ocean momentum equation (see \mdl{dynspg} for the ocean). … … 833 833 834 834 When using timesplitting and BDY package for open boundaries conditions, 835 the equivalent inverse barometer sea surface height $\eta_{ib}$ can be added to BDY ssh data: 835 the equivalent inverse barometer sea surface height $\eta_{ib}$ can be added to BDY ssh data: 836 836 \np{ln\_apr\_obc} might be set to true. 837 837 … … 851 851 852 852 The tidal forcing, generated by the gravity forces of the EarthMoon and EarthSun sytems, 853 is activated if \np{ln\_tide} and \np{ln\_tide\_pot} are both set to \forcode{.true.} in \n gn{nam\_tide}.853 is activated if \np{ln\_tide} and \np{ln\_tide\_pot} are both set to \forcode{.true.} in \nam{\_tide}. 854 854 This translates as an additional barotropic force in the momentum equations \ref{eq:PE_dyn} such that: 855 855 \[ … … 860 860 where $\Pi_{eq}$ stands for the equilibrium tidal forcing and 861 861 $\Pi_{sal}$ is a selfattraction and loading term (SAL). 862 862 863 863 The equilibrium tidal forcing is expressed as a sum over a subset of 864 864 constituents chosen from the set of available tidal constituents 865 defined in file \ textit{SBC/tide.h90} (this comprises the tidal865 defined in file \hf{SBC/tide} (this comprises the tidal 866 866 constituents \textit{M2, N2, 2N2, S2, K2, K1, O1, Q1, P1, M4, Mf, Mm, 867 867 Msqm, Mtm, S1, MU2, NU2, L2}, and \textit{T2}). Individual 868 868 constituents are selected by including their names in the array 869 \np{clname} in \n gn{nam\_tide} (e.g., \np{clname(1) = 'M2',870 clname(2)='S2'} to select solely the tidal consituents \textit{M2}869 \np{clname} in \nam{\_tide} (e.g., \np{clname}\forcode{(1) = 'M2', } 870 \np{clname}\forcode{(2) = 'S2'} to select solely the tidal consituents \textit{M2} 871 871 and \textit{S2}). Optionally, when \np{ln\_tide\_ramp} is set to 872 872 \forcode{.true.}, the equilibrium tidal forcing can be ramped up … … 880 880 computationally too expensive. Here, two options are available: 881 881 $\Pi_{sal}$ generated by an external model can be read in 882 (\np{ln\_read\_load =.true.}), or a ``scalar approximation'' can be883 used (\np{ln\_scal\_load =.true.}). In the latter case882 (\np{ln\_read\_load}\forcode{ =.true.}), or a ``scalar approximation'' can be 883 used (\np{ln\_scal\_load}\forcode{ =.true.}). In the latter case 884 884 \[ 885 885 \Pi_{sal} = \beta \eta, … … 900 900 %namsbc_rnf 901 901 902 \nlst{namsbc_rnf} 902 \nlst{namsbc_rnf} 903 903 % 904 904 905 %River runoff generally enters the ocean at a nonzero depth rather than through the surface. 905 %River runoff generally enters the ocean at a nonzero depth rather than through the surface. 906 906 %Many models, however, have traditionally inserted river runoff to the top model cell. 907 %This was the case in \NEMO prior to the version 3.3. The switch toward a input of runoff908 %throughout a nonzero depth has been motivated by the numerical and physical problems 909 %that arise when the top grid cells are of the order of one meter. This situation is common in 910 %coastal modelling and becomes more and more often open ocean and climate modelling 907 %This was the case in \NEMO\ prior to the version 3.3. The switch toward a input of runoff 908 %throughout a nonzero depth has been motivated by the numerical and physical problems 909 %that arise when the top grid cells are of the order of one meter. This situation is common in 910 %coastal modelling and becomes more and more often open ocean and climate modelling 911 911 %\footnote{At least a top cells thickness of 1~meter and a 3 hours forcing frequency are 912 912 %required to properly represent the diurnal cycle \citep{bernie.woolnough.ea_JC05}. see also \autoref{fig:SBC_dcy}.}. 913 913 914 914 915 %To do this we need to treat evaporation/precipitation fluxes and river runoff differently in the 916 %\mdl{tra\_sbc} module. We decided to separate them throughout the code, so that the variable 917 %\textit{emp} represented solely evaporation minus precipitation fluxes, and a new 2d variable 918 %rnf was added which represents the volume flux of river runoff (in kg/m2s to remain consistent with 919 %emp). This meant many uses of emp and emps needed to be changed, a list of all modules which use 915 %To do this we need to treat evaporation/precipitation fluxes and river runoff differently in the 916 %\mdl{tra\_sbc} module. We decided to separate them throughout the code, so that the variable 917 %\textit{emp} represented solely evaporation minus precipitation fluxes, and a new 2d variable 918 %rnf was added which represents the volume flux of river runoff (in kg/m2s to remain consistent with 919 %emp). This meant many uses of emp and emps needed to be changed, a list of all modules which use 920 920 %emp or emps and the changes made are below: 921 921 … … 924 924 River runoff generally enters the ocean at a nonzero depth rather than through the surface. 925 925 Many models, however, have traditionally inserted river runoff to the top model cell. 926 This was the case in \NEMO prior to the version 3.3,926 This was the case in \NEMO\ prior to the version 3.3, 927 927 and was combined with an option to increase vertical mixing near the river mouth. 928 928 929 929 However, with this method numerical and physical problems arise when the top grid cells are of the order of one meter. 930 This situation is common in coastal modelling and is becoming more common in open ocean and climate modelling 930 This situation is common in coastal modelling and is becoming more common in open ocean and climate modelling 931 931 \footnote{ 932 932 At least a top cells thickness of 1~meter and a 3 hours forcing frequency are required to … … 939 939 along with the depth (in metres) which the river should be added to. 940 940 941 Namelist variables in \n gn{namsbc\_rnf}, \np{ln\_rnf\_depth}, \np{ln\_rnf\_sal} and941 Namelist variables in \nam{sbc\_rnf}, \np{ln\_rnf\_depth}, \np{ln\_rnf\_sal} and 942 942 \np{ln\_rnf\_temp} control whether the river attributes (depth, salinity and temperature) are read in and used. 943 943 If these are set as false the river is added to the surface box only, assumed to be fresh (0~psu), 944 944 and/or taken as surface temperature respectively. 945 945 946 The runoff value and attributes are read in in sbcrnf. 946 The runoff value and attributes are read in in sbcrnf. 947 947 For temperature 999 is taken as missing data and the river temperature is taken to 948 948 be the surface temperatue at the river point. 949 For the depth parameter a value of 1 means the river is added to the surface box only, 950 and a value of 999 means the river is added through the entire water column. 949 For the depth parameter a value of 1 means the river is added to the surface box only, 950 and a value of 999 means the river is added through the entire water column. 951 951 After being read in the temperature and salinity variables are multiplied by the amount of runoff 952 952 (converted into m/s) to give the heat and salt content of the river runoff. … … 955 955 The variable \textit{h\_dep} is then calculated to be the depth (in metres) of 956 956 the bottom of the lowest box the river water is being added to 957 (\ie the total depth that river water is being added to in the model).957 (\ie\ the total depth that river water is being added to in the model). 958 958 959 959 The mass/volume addition due to the river runoff is, at each relevant depth level, added to … … 961 961 This increases the diffusion term in the vicinity of the river, thereby simulating a momentum flux. 962 962 The sea surface height is calculated using the sum of the horizontal divergence terms, 963 and so the river runoff indirectly forces an increase in sea surface height. 963 and so the river runoff indirectly forces an increase in sea surface height. 964 964 965 965 The \textit{hdivn} terms are used in the tracer advection modules to force vertical velocities. … … 983 983 This is done in the same way for both vvl and nonvvl. 984 984 The temperature and salinity are increased through the specified depth according to 985 the heat and salt content of the river. 985 the heat and salt content of the river. 986 986 987 987 In the nonlinear free surface case (vvl), … … 992 992 993 993 It is also possible for runnoff to be specified as a negative value for modelling flow through straits, 994 \ie modelling the Baltic flow in and out of the North Sea.994 \ie\ modelling the Baltic flow in and out of the North Sea. 995 995 When the flow is out of the domain there is no change in temperature and salinity, 996 996 regardless of the namelist options used, 997 as the ocean water leaving the domain removes heat and salt (at the same concentration) with it. 998 999 1000 %\colorbox{yellow}{Nevertheless, Pb of vertical resolution and 3D input : increase vertical mixing near river mouths to mimic a 3D river 997 as the ocean water leaving the domain removes heat and salt (at the same concentration) with it. 998 999 1000 %\colorbox{yellow}{Nevertheless, Pb of vertical resolution and 3D input : increase vertical mixing near river mouths to mimic a 3D river 1001 1001 1002 1002 %All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and at the same temperature as the sea surface.} … … 1010 1010 %\gmcomment{ word doc of runoffs: 1011 1011 % 1012 %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.1013 %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. 1012 %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. 1013 %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. 1014 1014 1015 1015 %The depth option makes it possible to have the river water affecting just the surface layer, throughout depth, or some specified point in between. … … 1030 1030 % 1031 1031 1032 The namelist variable in \n gn{namsbc}, \np{nn\_isf}, controls the ice shelf representation.1033 Description and result of sensitivity test to \np{nn\_isf} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1032 The namelist variable in \nam{sbc}, \np{nn\_isf}, controls the ice shelf representation. 1033 Description and result of sensitivity test to \np{nn\_isf} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1034 1034 The different options are illustrated in \autoref{fig:SBC_isf}. 1035 1035 … … 1039 1039 The ice shelf cavity is represented (\np{ln\_isfcav}\forcode{ = .true.} needed). 1040 1040 The fwf and heat flux are depending of the local water properties. 1041 1041 1042 1042 Two different bulk formulae are available: 1043 1043 … … 1048 1048 \item[\np{nn\_isfblk}\forcode{ = 2}]: 1049 1049 The melt rate and the heat flux are based on a 3 equations formulation 1050 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 1050 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 1051 1051 A complete description is available in \citet{jenkins_JGR91}. 1052 1052 \end{description} 1053 1053 1054 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1054 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1055 1055 Its thickness is defined by \np{rn\_hisf\_tbl}. 1056 1056 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn\_hisf\_tbl} m. … … 1060 1060 If \np{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 1061 1061 1062 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1062 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1063 1063 There are 3 different ways to compute the exchange coeficient: 1064 1064 \begin{description} 1065 1065 \item[\np{nn\_gammablk}\forcode{ = 0}]: 1066 The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}. 1066 The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}. 1067 1067 \[ 1068 1068 % \label{eq:sbc_isf_gamma_iso} … … 1076 1076 The salt and heat exchange coefficients are velocity dependent and defined as 1077 1077 \[ 1078 \gamma^{T} = \np{rn\_gammat0} \times u_{*} 1078 \gamma^{T} = \np{rn\_gammat0} \times u_{*} 1079 1079 \] 1080 1080 \[ … … 1086 1086 The salt and heat exchange coefficients are velocity and stability dependent and defined as: 1087 1087 \[ 1088 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1088 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1089 1089 \] 1090 1090 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters), 1091 1091 $\Gamma_{Turb}$ the contribution of the ocean stability and 1092 1092 $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 1093 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1094 This formulation has not been extensively tested in NEMO(not recommended).1093 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1094 This formulation has not been extensively tested in \NEMO\ (not recommended). 1095 1095 \end{description} 1096 1096 \item[\np{nn\_isf}\forcode{ = 2}]: … … 1123 1123 This can be useful if the water masses on the shelf are not realistic or 1124 1124 the resolution (horizontal/vertical) are too coarse to have realistic melting or 1125 for studies where you need to control your heat and fw input.\\ 1125 for studies where you need to control your heat and fw input.\\ 1126 1126 1127 1127 The ice shelf melt is implemented as a volume flux as for the runoff. … … 1160 1160 \item[Step 1]: the ice sheet model send a new bathymetry and ice shelf draft netcdf file. 1161 1161 \item[Step 2]: a new domcfg.nc file is built using the DOMAINcfg tools. 1162 \item[Step 3]: NEMOrun for a specific period and output the average melt rate over the period.1162 \item[Step 3]: \NEMO\ run for a specific period and output the average melt rate over the period. 1163 1163 \item[Step 4]: the ice sheet model run using the melt rate outputed in step 4. 1164 1164 \item[Step 5]: go back to 1. … … 1178 1178 mask, T/S, U/V and ssh are set to 0. 1179 1179 Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1180 \item[Wet a cell]: 1180 \item[Wet a cell]: 1181 1181 mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$ and U/V set to 0. 1182 If no neighbours, T/S is extrapolated from old top cell value. 1182 If no neighbours, T/S is extrapolated from old top cell value. 1183 1183 If no neighbours along i,j and k (both previous test failed), T/S/U/V/ssh and mask are set to 0. 1184 1184 \item[Dry a column]: … … 1197 1197 The default number is set up for the MISOMIP idealised experiments. 1198 1198 This coupling procedure is able to take into account grounding line and calving front migration. 1199 However, it is a nonconservative processe. 1199 However, it is a nonconservative processe. 1200 1200 This could lead to a trend in heat/salt content and volume.\\ 1201 1201 … … 1203 1203 a simple conservation scheme is available with \np{ln\_hsb}\forcode{ = .true.}. 1204 1204 The heat/salt/vol. gain/loss is diagnosed, as well as the location. 1205 A correction increment is computed and apply each time step during the next \np{rn\_fiscpl} time steps. 1205 A correction increment is computed and apply each time step during the next \np{rn\_fiscpl} time steps. 1206 1206 For safety, it is advised to set \np{rn\_fiscpl} equal to the coupling period (smallest increment possible). 1207 1207 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). … … 1219 1219 % 1220 1220 1221 Icebergs are modelled as lagrangian particles in NEMO\citep{marsh.ivchenko.ea_GMD15}.1221 Icebergs are modelled as lagrangian particles in \NEMO\ \citep{marsh.ivchenko.ea_GMD15}. 1222 1222 Their physical behaviour is controlled by equations as described in \citet{martin.adcroft_OM10} ). 1223 (Note that the authors kindly provided a copy of their code to act as a basis for implementation in NEMO).1223 (Note that the authors kindly provided a copy of their code to act as a basis for implementation in \NEMO). 1224 1224 Icebergs are initially spawned into one of ten classes which have specific mass and thickness as 1225 described in the \n gn{namberg} namelist: \np{rn\_initial\_mass} and \np{rn\_initial\_thickness}.1225 described in the \nam{berg} namelist: \np{rn\_initial\_mass} and \np{rn\_initial\_thickness}. 1226 1226 Each class has an associated scaling (\np{rn\_mass\_scaling}), 1227 1227 which is an integer representing how many icebergs of this class are being described as one lagrangian point … … 1247 1247 At each time step, a test is performed to see if there is enough ice mass to 1248 1248 calve an iceberg of each class in order (1 to 10). 1249 Note that this is the initial mass multiplied by the number each particle represents (\ie the scaling).1249 Note that this is the initial mass multiplied by the number each particle represents (\ie\ the scaling). 1250 1250 If there is enough ice, a new iceberg is spawned and the total available ice reduced accordingly. 1251 1251 \end{description} … … 1256 1256 or (if \np{rn\_bits\_erosion\_fraction}~$>$~0) into melt and additionally small ice bits 1257 1257 which are assumed to propagate with their larger parent and thus delay fluxing into the ocean. 1258 Melt water (and other variables on the configuration grid) are written into the main NEMOmodel output files.1258 Melt water (and other variables on the configuration grid) are written into the main \NEMO\ model output files. 1259 1259 1260 1260 Extensive diagnostics can be produced. … … 1290 1290 % 1291 1291 1292 Ocean waves represent the interface between the ocean and the atmosphere, so NEMO is extended to incorporate1293 physical processes related to ocean surface waves, namely the surface stress modified by growth and 1294 dissipation of the oceanic wave field, the StokesCoriolis force and the Stokes drift impact on mass and 1295 tracer advection; moreover the neutral surface drag coefficient from a wave model can be used to evaluate 1292 Ocean waves represent the interface between the ocean and the atmosphere, so \NEMO\ is extended to incorporate 1293 physical processes related to ocean surface waves, namely the surface stress modified by growth and 1294 dissipation of the oceanic wave field, the StokesCoriolis force and the Stokes drift impact on mass and 1295 tracer advection; moreover the neutral surface drag coefficient from a wave model can be used to evaluate 1296 1296 the wind stress. 1297 1297 1298 Physical processes related to ocean surface waves can be accounted by setting the logical variable 1299 \np{ln\_wave} \forcode{= .true.} in \ngn{namsbc} namelist. In addition, specific flags accounting for1298 Physical processes related to ocean surface waves can be accounted by setting the logical variable 1299 \np{ln\_wave}\forcode{ = .true.} in \nam{sbc} namelist. In addition, specific flags accounting for 1300 1300 different processes should be activated as explained in the following sections. 1301 1301 1302 1302 Wave fields can be provided either in forced or coupled mode: 1303 1303 \begin{description} 1304 \item[forced mode]: wave fields should be defined through the \n gn{namsbc\_wave} namelist1305 for external data names, locations, frequency, interpolation and all the miscellanous options allowed by 1306 Input Data generic Interface (see \autoref{sec:SBC_input}). 1307 \item[coupled mode]: NEMO and an external wave model can be coupled by setting \np{ln\_cpl} \forcode{= .true.}1308 in \n gn{namsbc} namelist and filling the \ngn{namsbc\_cpl} namelist.1304 \item[forced mode]: wave fields should be defined through the \nam{sbc\_wave} namelist 1305 for external data names, locations, frequency, interpolation and all the miscellanous options allowed by 1306 Input Data generic Interface (see \autoref{sec:SBC_input}). 1307 \item[coupled mode]: \NEMO\ and an external wave model can be coupled by setting \np{ln\_cpl} \forcode{= .true.} 1308 in \nam{sbc} namelist and filling the \nam{sbc\_cpl} namelist. 1309 1309 \end{description} 1310 1310 … … 1318 1318 \label{subsec:SBC_wave_cdgw} 1319 1319 1320 The neutral surface drag coefficient provided from an external data source (\ie a wave model),1321 can be used by setting the logical variable \np{ln\_cdgw} \forcode{= .true.} in \n gn{namsbc} namelist.1322 Then using the routine \rou{sbcblk\_algo\_ncar} and starting from the neutral drag coefficent provided, 1323 the drag coefficient is computed according to the stable/unstable conditions of the 1324 airsea interface following \citet{large.yeager_rpt04}. 1320 The neutral surface drag coefficient provided from an external data source (\ie\ a wave model), 1321 can be used by setting the logical variable \np{ln\_cdgw} \forcode{= .true.} in \nam{sbc} namelist. 1322 Then using the routine \rou{sbcblk\_algo\_ncar} and starting from the neutral drag coefficent provided, 1323 the drag coefficient is computed according to the stable/unstable conditions of the 1324 airsea interface following \citet{large.yeager_rpt04}. 1325 1325 1326 1326 … … 1332 1332 \label{subsec:SBC_wave_sdw} 1333 1333 1334 The Stokes drift is a wave driven mechanism of mass and momentum transport \citep{stokes_ibk09}. 1335 It is defined as the difference between the average velocity of a fluid parcel (Lagrangian velocity) 1336 and the current measured at a fixed point (Eulerian velocity). 1337 As waves travel, the water particles that make up the waves travel in orbital motions but 1338 without a closed path. Their movement is enhanced at the top of the orbit and slowed slightly 1339 at the bottom, so the result is a net forward motion of water particles, referred to as the Stokes drift. 1340 An accurate evaluation of the Stokes drift and the inclusion of related processes may lead to improved 1334 The Stokes drift is a wave driven mechanism of mass and momentum transport \citep{stokes_ibk09}. 1335 It is defined as the difference between the average velocity of a fluid parcel (Lagrangian velocity) 1336 and the current measured at a fixed point (Eulerian velocity). 1337 As waves travel, the water particles that make up the waves travel in orbital motions but 1338 without a closed path. Their movement is enhanced at the top of the orbit and slowed slightly 1339 at the bottom, so the result is a net forward motion of water particles, referred to as the Stokes drift. 1340 An accurate evaluation of the Stokes drift and the inclusion of related processes may lead to improved 1341 1341 representation of surface physics in ocean general circulation models. %GS: reference needed 1342 The Stokes drift velocity $\mathbf{U}_{st}$ in deep water can be computed from the wave spectrum and may be written as: 1342 The Stokes drift velocity $\mathbf{U}_{st}$ in deep water can be computed from the wave spectrum and may be written as: 1343 1343 1344 1344 \[ … … 1349 1349 \] 1350 1350 1351 where: ${\theta}$ is the wave direction, $f$ is the wave intrinsic frequency, 1352 $\mathrm{S}($f$,\theta)$ is the 2D frequencydirection spectrum, 1353 $k$ is the mean wavenumber defined as: 1351 where: ${\theta}$ is the wave direction, $f$ is the wave intrinsic frequency, 1352 $\mathrm{S}($f$,\theta)$ is the 2D frequencydirection spectrum, 1353 $k$ is the mean wavenumber defined as: 1354 1354 $k=\frac{2\pi}{\lambda}$ (being $\lambda$ the wavelength). \\ 1355 1355 1356 In order to evaluate the Stokes drift in a realistic ocean wave field, the wave spectral shape is required 1357 and its computation quickly becomes expensive as the 2D spectrum must be integrated for each vertical level. 1356 In order to evaluate the Stokes drift in a realistic ocean wave field, the wave spectral shape is required 1357 and its computation quickly becomes expensive as the 2D spectrum must be integrated for each vertical level. 1358 1358 To simplify, it is customary to use approximations to the full Stokes profile. 1359 Three possible parameterizations for the calculation for the approximate Stokes drift velocity profile 1360 are included in the code through the \np{nn\_sdrift} parameter once provided the surface Stokes drift 1361 $\mathbf{U}_{st _{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra 1362 and makes possible the estimation of the surface Stokes drift for random directional waves in 1359 Three possible parameterizations for the calculation for the approximate Stokes drift velocity profile 1360 are included in the code through the \np{nn\_sdrift} parameter once provided the surface Stokes drift 1361 $\mathbf{U}_{st _{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra 1362 and makes possible the estimation of the surface Stokes drift for random directional waves in 1363 1363 realistic wave conditions: 1364 1364 1365 1365 \begin{description} 1366 \item[\np{nn\_sdrift} = 0]: exponential integral profile parameterization proposed by 1366 \item[\np{nn\_sdrift} = 0]: exponential integral profile parameterization proposed by 1367 1367 \citet{breivik.janssen.ea_JPO14}: 1368 1368 1369 1369 \[ 1370 1370 % \label{eq:sbc_wave_sdw_0a} 1371 \mathbf{U}_{st} \cong \mathbf{U}_{st _{z=0}} \frac{\mathrm{e}^{2k_ez}} {18k_ez} 1371 \mathbf{U}_{st} \cong \mathbf{U}_{st _{z=0}} \frac{\mathrm{e}^{2k_ez}} {18k_ez} 1372 1372 \] 1373 1373 … … 1378 1378 k_e = \frac{\mathbf{U}_{\left.st\right_{z=0}}} {T_{st}} 1379 1379 \quad \text{and }\ 1380 T_{st} = \frac{1}{16} \bar{\omega} H_s^2 1380 T_{st} = \frac{1}{16} \bar{\omega} H_s^2 1381 1381 \] 1382 1382 1383 1383 where $H_s$ is the significant wave height and $\omega$ is the wave frequency. 1384 1384 1385 \item[\np{nn\_sdrift} = 1]: velocity profile based on the Phillips spectrum which is considered to be a 1385 \item[\np{nn\_sdrift} = 1]: velocity profile based on the Phillips spectrum which is considered to be a 1386 1386 reasonable estimate of the part of the spectrum mostly contributing to the Stokes drift velocity near the surface 1387 1387 \citep{breivik.bidlot.ea_OM16}: … … 1395 1395 where $erf$ is the complementary error function and $k_p$ is the peak wavenumber. 1396 1396 1397 \item[\np{nn\_sdrift} = 2]: velocity profile based on the Phillips spectrum as for \np{nn\_sdrift} = 1 1397 \item[\np{nn\_sdrift} = 2]: velocity profile based on the Phillips spectrum as for \np{nn\_sdrift} = 1 1398 1398 but using the wave frequency from a wave model. 1399 1399 1400 1400 \end{description} 1401 1401 1402 The Stokes drift enters the waveaveraged momentum equation, as well as the tracer advection equations 1403 and its effect on the evolution of the seasurface height ${\eta}$ is considered as follows: 1402 The Stokes drift enters the waveaveraged momentum equation, as well as the tracer advection equations 1403 and its effect on the evolution of the seasurface height ${\eta}$ is considered as follows: 1404 1404 1405 1405 \[ … … 1409 1409 \] 1410 1410 1411 The tracer advection equation is also modified in order for Eulerian ocean models to properly account 1412 for unresolved wave effect. The divergence of the wave tracer flux equals the mean tracer advection 1413 that is induced by the threedimensional Stokes velocity. 1414 The advective equation for a tracer $c$ combining the effects of the mean current and sea surface waves 1415 can be formulated as follows: 1411 The tracer advection equation is also modified in order for Eulerian ocean models to properly account 1412 for unresolved wave effect. The divergence of the wave tracer flux equals the mean tracer advection 1413 that is induced by the threedimensional Stokes velocity. 1414 The advective equation for a tracer $c$ combining the effects of the mean current and sea surface waves 1415 can be formulated as follows: 1416 1416 1417 1417 \[ … … 1429 1429 \label{subsec:SBC_wave_stcor} 1430 1430 1431 In a rotating ocean, waves exert a waveinduced stress on the mean ocean circulation which results 1432 in a force equal to $\mathbf{U}_{st}$×$f$, where $f$ is the Coriolis parameter. 1433 This additional force may have impact on the Ekman turning of the surface current. 1434 In order to include this term, once evaluated the Stokes drift (using one of the 3 possible 1435 approximations described in \autoref{subsec:SBC_wave_sdw}), 1431 In a rotating ocean, waves exert a waveinduced stress on the mean ocean circulation which results 1432 in a force equal to $\mathbf{U}_{st}$×$f$, where $f$ is the Coriolis parameter. 1433 This additional force may have impact on the Ekman turning of the surface current. 1434 In order to include this term, once evaluated the Stokes drift (using one of the 3 possible 1435 approximations described in \autoref{subsec:SBC_wave_sdw}), 1436 1436 \np{ln\_stcor}\forcode{ = .true.} has to be set. 1437 1437 … … 1444 1444 \label{subsec:SBC_wave_tauw} 1445 1445 1446 The surface stress felt by the ocean is the atmospheric stress minus the net stress going 1447 into the waves \citep{janssen.breivik.ea_rpt13}. Therefore, when waves are growing, momentum and energy is spent and is not 1448 available for forcing the mean circulation, while in the opposite case of a decaying sea 1449 state, more momentum is available for forcing the ocean. 1450 Only when the sea state is in equilibrium, the ocean is forced by the atmospheric stress, 1451 but in practice, an equilibrium sea state is a fairly rare event. 1452 So the atmospheric stress felt by the ocean circulation $\tau_{oc,a}$ can be expressed as: 1446 The surface stress felt by the ocean is the atmospheric stress minus the net stress going 1447 into the waves \citep{janssen.breivik.ea_rpt13}. Therefore, when waves are growing, momentum and energy is spent and is not 1448 available for forcing the mean circulation, while in the opposite case of a decaying sea 1449 state, more momentum is available for forcing the ocean. 1450 Only when the sea state is in equilibrium, the ocean is forced by the atmospheric stress, 1451 but in practice, an equilibrium sea state is a fairly rare event. 1452 So the atmospheric stress felt by the ocean circulation $\tau_{oc,a}$ can be expressed as: 1453 1453 1454 1454 \[ … … 1466 1466 1467 1467 where: $c_p$ is the phase speed of the gravity waves, 1468 $S_{in}$, $S_{nl}$ and $S_{diss}$ are three source terms that represent 1469 the physics of ocean waves. The first one, $S_{in}$, describes the generation 1470 of ocean waves by wind and therefore represents the momentum and energy transfer 1471 from air to ocean waves; the second term $S_{nl}$ denotes 1472 the nonlinear transfer by resonant fourwave interactions; while the third term $S_{diss}$ 1473 describes the dissipation of waves by processes such as whitecapping, large scale breaking 1468 $S_{in}$, $S_{nl}$ and $S_{diss}$ are three source terms that represent 1469 the physics of ocean waves. The first one, $S_{in}$, describes the generation 1470 of ocean waves by wind and therefore represents the momentum and energy transfer 1471 from air to ocean waves; the second term $S_{nl}$ denotes 1472 the nonlinear transfer by resonant fourwave interactions; while the third term $S_{diss}$ 1473 describes the dissipation of waves by processes such as whitecapping, large scale breaking 1474 1474 eddyinduced damping. 1475 1475 1476 The wave stress derived from an external wave model can be provided either through the normalized 1477 wave stress into the ocean by setting \np{ln\_tauwoc}\forcode{ = .true.}, or through the zonal and 1476 The wave stress derived from an external wave model can be provided either through the normalized 1477 wave stress into the ocean by setting \np{ln\_tauwoc}\forcode{ = .true.}, or through the zonal and 1478 1478 meridional stress components by setting \np{ln\_tauw}\forcode{ = .true.}. 1479 1479 … … 1495 1495 %namsbc 1496 1496 % 1497 \nlst{namsbc} 1497 \nlst{namsbc} 1498 1498 % 1499 1499 … … 1520 1520 as higher frequency variations can be reconstructed from them, 1521 1521 assuming that the diurnal cycle of SWF is a scaling of the top of the atmosphere diurnal cycle of incident SWF. 1522 The \cite{bernie.guilyardi.ea_CD07} reconstruction algorithm is available in \NEMO by1523 setting \np{ln\_dm2dc}\forcode{ = .true.} (a \textit{\n gn{namsbc}} namelist variable) when1522 The \cite{bernie.guilyardi.ea_CD07} reconstruction algorithm is available in \NEMO\ by 1523 setting \np{ln\_dm2dc}\forcode{ = .true.} (a \textit{\nam{sbc}} namelist variable) when 1524 1524 using a bulk formulation (\np{ln\_blk}\forcode{ = .true.}) or 1525 1525 the flux formulation (\np{ln\_flx}\forcode{ = .true.}). … … 1529 1529 a given time step is the mean value of the analytical cycle over this time step (\autoref{fig:SBC_diurnal}). 1530 1530 The use of diurnal cycle reconstruction requires the input SWF to be daily 1531 (\ie a frequency of 24 hours and a time interpolation set to true in \np{sn\_qsr} namelist parameter).1531 (\ie\ a frequency of 24 hours and a time interpolation set to true in \np{sn\_qsr} namelist parameter). 1532 1532 Furthermore, it is recommended to have a least 8 surface module time steps per day, 1533 1533 that is $\rdt \ nn\_fsbc < 10,800~s = 3~h$. … … 1565 1565 be defined relative to a rectilinear grid. 1566 1566 To activate this option, a nonempty string is supplied in the rotation pair column of the relevant namelist. 1567 The eastward component must start with "U" and the northward component with "V". 1567 The eastward component must start with "U" and the northward component with "V". 1568 1568 The remaining characters in the strings are used to identify which pair of components go together. 1569 1569 So for example, strings "U1" and "V1" next to "utau" and "vtau" would pair the wind stress components together and … … 1582 1582 %namsbc_ssr 1583 1583 1584 \nlst{namsbc_ssr} 1584 \nlst{namsbc_ssr} 1585 1585 % 1586 1586 1587 Options are defined through the \n gn{namsbc\_ssr} namelist variables.1587 Options are defined through the \nam{sbc\_ssr} namelist variables. 1588 1588 On forced mode using a flux formulation (\np{ln\_flx}\forcode{ = .true.}), 1589 1589 a feedback term \emph{must} be added to the surface heat flux $Q_{ns}^o$: … … 1595 1595 $T$ is the model surface layer temperature and 1596 1596 $\frac{dQ}{dT}$ is a negative feedback coefficient usually taken equal to $40~W/m^2/K$. 1597 For a $50~m$ mixedlayer depth, this value corresponds to a relaxation time scale of two months. 1598 This term ensures that if $T$ perfectly matches the supplied SST, then $Q$ is equal to $Q_o$. 1597 For a $50~m$ mixedlayer depth, this value corresponds to a relaxation time scale of two months. 1598 This term ensures that if $T$ perfectly matches the supplied SST, then $Q$ is equal to $Q_o$. 1599 1599 1600 1600 In the fresh water budget, a feedback term can also be added. … … 1627 1627 The presence at the sea surface of an ice covered area modifies all the fluxes transmitted to the ocean. 1628 1628 There are several way to handle seaice in the system depending on 1629 the value of the \np{nn\_ice} namelist parameter found in \n gn{namsbc} namelist.1629 the value of the \np{nn\_ice} namelist parameter found in \nam{sbc} namelist. 1630 1630 \begin{description} 1631 \item[nn {\_}ice = 0]1631 \item[nn\_ice = 0] 1632 1632 there will never be seaice in the computational domain. 1633 1633 This is a typical namelist value used for tropical ocean domain. 1634 1634 The surface fluxes are simply specified for an icefree ocean. 1635 1635 No specific things is done for seaice. 1636 \item[nn {\_}ice = 1]1636 \item[nn\_ice = 1] 1637 1637 seaice can exist in the computational domain, but no seaice model is used. 1638 1638 An observed ice covered area is read in a file. … … 1645 1645 This manner of managing seaice area, just by using a IF case, 1646 1646 is usually referred as the \textit{iceif} model. 1647 It can be found in the \mdl{sbcice {\_}if} module.1648 \item[nn {\_}ice = 2 or more]1647 It can be found in the \mdl{sbcice\_if} module. 1648 \item[nn\_ice = 2 or more] 1649 1649 A full sea ice model is used. 1650 1650 This model computes the iceocean fluxes, … … 1652 1652 provide the surface averaged ocean fluxes. 1653 1653 Note that the activation of a seaice model is done by defining a CPP key (\key{si3} or \key{cice}). 1654 The activation automatically overwrites the read value of nn {\_}ice to its appropriate value1655 (\ie $2$ for SI3 or $3$ for CICE).1654 The activation automatically overwrites the read value of nn\_ice to its appropriate value 1655 (\ie\ $2$ for SI3 or $3$ for CICE). 1656 1656 \end{description} 1657 1657 … … 1667 1667 \label{subsec:SBC_cice} 1668 1668 1669 It is possible to couple a regional or global NEMOconfiguration (without AGRIF)1669 It is possible to couple a regional or global \NEMO\ configuration (without AGRIF) 1670 1670 to the CICE seaice model by using \key{cice}. 1671 1671 The CICE code can be obtained from \href{http://oceans11.lanl.gov/trac/CICE/}{LANL} and 1672 1672 the additional 'hadgem3' drivers will be required, even with the latest code release. 1673 Input grid files consistent with those used in NEMOwill also be needed,1673 Input grid files consistent with those used in \NEMO\ will also be needed, 1674 1674 and CICE CPP keys \textbf{ORCA\_GRID}, \textbf{CICE\_IN\_NEMO} and \textbf{coupled} should be used 1675 1675 (seek advice from UKMO if necessary). 1676 Currently, the code is only designed to work when using the NCAR forcing option for NEMO%GS: still true ?1676 Currently, the code is only designed to work when using the NCAR forcing option for \NEMO\ %GS: still true ? 1677 1677 (with \textit{calc\_strair}\forcode{ = .true.} and \textit{calc\_Tsfc}\forcode{ = .true.} in the CICE namelist), 1678 or alternatively when NEMOis coupled to the HadGAM3 atmosphere model1678 or alternatively when \NEMO\ is coupled to the HadGAM3 atmosphere model 1679 1679 (with \textit{calc\_strair}\forcode{ = .false.} and \textit{calc\_Tsfc}\forcode{ = false}). 1680 1680 The code is intended to be used with \np{nn\_fsbc} set to 1 … … 1683 1683 the user should check that results are not significantly different to the standard case). 1684 1684 1685 There are two options for the technical coupling between NEMOand CICE.1685 There are two options for the technical coupling between \NEMO\ and CICE. 1686 1686 The standard version allows complete flexibility for the domain decompositions in the individual models, 1687 1687 but this is at the expense of global gather and scatter operations in the coupling which 1688 1688 become very expensive on larger numbers of processors. 1689 The alternative option (using \key{nemocice\_decomp} for both NEMOand CICE) ensures that1689 The alternative option (using \key{nemocice\_decomp} for both \NEMO\ and CICE) ensures that 1690 1690 the domain decomposition is identical in both models (provided domain parameters are set appropriately, 1691 1691 and \textit{processor\_shape~=~squareice} and \textit{distribution\_wght~=~block} in the CICE namelist) and … … 1696 1696 1697 1697 %  1698 % Freshwater budget control 1698 % Freshwater budget control 1699 1699 %  1700 1700 \subsection[Freshwater budget control (\textit{sbcfwb.F90})] … … 1705 1705 prevent unrealistic drift of the sea surface height due to inaccuracy in the freshwater fluxes. 1706 1706 In \NEMO, two way of controlling the freshwater budget are proposed: 1707 1707 1708 1708 \begin{description} 1709 1709 \item[\np{nn\_fwb}\forcode{ = 0}] … … 1711 1711 The mean sea level is free to drift, and will certainly do so. 1712 1712 \item[\np{nn\_fwb}\forcode{ = 1}] 1713 global mean \textit{emp} set to zero at each model time step. 1713 global mean \textit{emp} set to zero at each model time step. 1714 1714 %GS: comment below still relevant ? 1715 %Note that with a seaice 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 iceocean coupling). 1715 %Note that with a seaice 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 iceocean coupling). 1716 1716 \item[\np{nn\_fwb}\forcode{ = 2}] 1717 1717 freshwater budget is adjusted from the previous year annual mean budget which 1718 1718 is read in the \textit{EMPave\_old.dat} file. 1719 1719 As the model uses the Boussinesq approximation, the annual mean fresh water budget is simply evaluated from 1720 the change in the mean sea level at January the first and saved in the \textit{EMPav.dat} file. 1720 the change in the mean sea level at January the first and saved in the \textit{EMPav.dat} file. 1721 1721 \end{description} 1722 1722 1723 1723 % Griffies doc: 1724 % When running oceanice simulations, we are not explicitly representing land processes, 1725 % such as rivers, catchment areas, snow accumulation, etc. However, to reduce model drift, 1726 % it is important to balance the hydrological cycle in oceanice models. 1727 % We thus need to prescribe some form of global normalization to the precipitation minus evaporation plus river runoff. 1728 % The result of the normalization should be a global integrated zero net water input to the oceanice system over 1729 % a chosen time scale. 1730 % How often the normalization is done is a matter of choice. In mom4p1, we choose to do so at each model time step, 1731 % so that there is always a zero net input of water to the oceanice system. 1732 % Others choose to normalize over an annual cycle, in which case the net imbalance over an annual cycle is used 1733 % to alter the subsequent year�s water budget in an attempt to damp the annual water imbalance. 1734 % Note that the annual budget approach may be inappropriate with interannually varying precipitation forcing. 1735 % When running oceanice coupled models, it is incorrect to include the water transport between the ocean 1736 % and ice models when aiming to balance the hydrological cycle. 1737 % The reason is that it is the sum of the water in the ocean plus ice that should be balanced when running oceanice models, 1738 % not the water in any one subcomponent. As an extreme example to illustrate the issue, 1739 % consider an oceanice model with zero initial sea ice. As the oceanice model spins up, 1740 % there should be a net accumulation of water in the growing sea ice, and thus a net loss of water from the ocean. 1741 % The total water contained in the ocean plus ice system is constant, but there is an exchange of water between 1742 % the subcomponents. This exchange should not be part of the normalization used to balance the hydrological cycle 1743 % in oceanice models. 1724 % When running oceanice simulations, we are not explicitly representing land processes, 1725 % such as rivers, catchment areas, snow accumulation, etc. However, to reduce model drift, 1726 % it is important to balance the hydrological cycle in oceanice models. 1727 % We thus need to prescribe some form of global normalization to the precipitation minus evaporation plus river runoff. 1728 % The result of the normalization should be a global integrated zero net water input to the oceanice system over 1729 % a chosen time scale. 1730 % How often the normalization is done is a matter of choice. In mom4p1, we choose to do so at each model time step, 1731 % so that there is always a zero net input of water to the oceanice system. 1732 % Others choose to normalize over an annual cycle, in which case the net imbalance over an annual cycle is used 1733 % to alter the subsequent year�s water budget in an attempt to damp the annual water imbalance. 1734 % Note that the annual budget approach may be inappropriate with interannually varying precipitation forcing. 1735 % When running oceanice coupled models, it is incorrect to include the water transport between the ocean 1736 % and ice models when aiming to balance the hydrological cycle. 1737 % The reason is that it is the sum of the water in the ocean plus ice that should be balanced when running oceanice models, 1738 % not the water in any one subcomponent. As an extreme example to illustrate the issue, 1739 % consider an oceanice model with zero initial sea ice. As the oceanice model spins up, 1740 % there should be a net accumulation of water in the growing sea ice, and thus a net loss of water from the ocean. 1741 % The total water contained in the ocean plus ice system is constant, but there is an exchange of water between 1742 % the subcomponents. This exchange should not be part of the normalization used to balance the hydrological cycle 1743 % in oceanice models. 1744 1744 1745 1745
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