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- 2016-02-24T08:56:48+01:00 (8 years ago)
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branches/2016/dev_r6325_SIMPLIF_1/DOC/TexFiles/Chapters/Chap_SBC.tex
r6320 r6347 51 51 \item the modification of fluxes below ice-covered areas (using observed ice-cover or a sea-ice model) (\np{nn\_ice}~=~0,1, 2 or 3) ; 52 52 \item the addition of river runoffs as surface freshwater fluxes or lateral inflow (\np{ln\_rnf}~=~true) ; 53 \item the addition of isf melting as lateral inflow (parameterisation) or as fluxes applied at the land-ice ocean interface (\np{ln\_isf}) ; 53 \item the addition of isf melting as lateral inflow (parameterisation) (\np{nn\_isf}~=~2 or 3 and \np{ln\_isfcav}~=~false) 54 or as fluxes applied at the land-ice ocean interface (\np{nn\_isf}~=~1 or 4 and \np{ln\_isfcav}~=~true) ; 54 55 \item the addition of a freshwater flux adjustment in order to avoid a mean sea-level drift (\np{nn\_fwb}~=~0,~1~or~2) ; 55 56 \item the transformation of the solar radiation (if provided as daily mean) into a diurnal cycle (\np{ln\_dm2dc}~=~true) ; … … 128 129 The ocean model provides, at each time step, to the surface module (\mdl{sbcmod}) 129 130 the surface currents, temperature and salinity. 130 These variables are averaged over \np{n f\_sbc} time-step (\ref{Tab_ssm}),131 These variables are averaged over \np{nn\_fsbc} time-step (\ref{Tab_ssm}), 131 132 and it is these averaged fields which are used to computes the surface fluxes 132 at a frequency of \np{n f\_sbc} time-step.133 at a frequency of \np{nn\_fsbc} time-step. 133 134 134 135 … … 144 145 \caption{ \label{Tab_ssm} 145 146 Ocean variables provided by the ocean to the surface module (SBC). 146 The variable are averaged over n f{\_}sbc time step, $i.e.$ the frequency of147 computation of surface fluxes.}147 The variable are averaged over nn{\_}fsbc time step, 148 $i.e.$ the frequency of computation of surface fluxes.} 148 149 \end{center} \end{table} 149 150 %-------------------------------------------------------------------------------------------------------------- … … 557 558 reanalysis and satellite data. They use an inertial dissipative method to compute 558 559 the turbulent transfer coefficients (momentum, sensible heat and evaporation) 559 from the 10 met rewind speed, air temperature and specific humidity.560 from the 10 meters wind speed, air temperature and specific humidity. 560 561 This \citet{Large_Yeager_Rep04} dataset is available through the 561 562 \href{http://nomads.gfdl.noaa.gov/nomads/forms/mom4/CORE.html}{GFDL web site}. … … 592 593 or larger than the one of the input atmospheric fields. 593 594 595 The \np{sn\_wndi}, \np{sn\_wndj}, \np{sn\_qsr}, \np{sn\_qlw}, \np{sn\_tair}, \np{sn\_humi}, 596 \np{sn\_prec}, \np{sn\_snow}, \np{sn\_tdif} parameters describe the fields 597 and the way they have to be used (spatial and temporal interpolations). 598 599 \np{cn\_dir} is the directory of location of bulk files 600 \np{ln\_taudif} is the flag to specify if we use Hight Frequency (HF) tau information (.true.) or not (.false.) 601 \np{rn\_zqt}: is the height of humidity and temperature measurements (m) 602 \np{rn\_zu}: is the height of wind measurements (m) 603 604 Three multiplicative factors are availables : 605 \np{rn\_pfac} and \np{rn\_efac} allows to adjust (if necessary) the global freshwater budget 606 by increasing/reducing the precipitations (total and snow) and or evaporation, respectively. 607 The third one,\np{rn\_vfac}, control to which extend the ice/ocean velocities are taken into account 608 in the calculation of surface wind stress. Its range should be between zero and one, 609 and it is recommended to set it to 0. 610 594 611 % ------------------------------------------------------------------------------------------------------------- 595 612 % CLIO Bulk formulea … … 926 943 \begin{description} 927 944 \item[\np{nn\_isf}~=~1] 928 The ice shelf cavit y is represented (\np{ln\_isfcav}~=~true needed). The fwf and heat flux are computed. Two different bulk formula are available:945 The ice shelf cavities are explicitly represented. The fwf and heat flux are computed. Two different bulk formula are available: 929 946 \begin{description} 930 947 \item[\np{nn\_isfblk}~=~1] … … 934 951 \item[\np{nn\_isfblk}~=~2] 935 952 The bulk formula used to compute the melt is based the one described in \citet{Jenkins1991}. 936 This formulation is based on a 3 equations formulation (a heat flux budget, a salt flux budget 937 and a linearised freezing point temperature equation). 953 This formulation is based on a 3 equations formulation (a heat flux budget, a salt flux budget and a linearised freezing point temperature equation). 938 954 \end{description} 939 955 … … 971 987 972 988 \item[\np{nn\_isf}~=~4] 973 The ice shelf cavity is opened (\np{ln\_isfcav}~=~true needed). However, the fwf is not computed but specified from file \np{sn\_fwfisf}).989 The ice shelf cavity is opened. However, the fwf is not computed but specified from file \np{sn\_fwfisf}). 974 990 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$.\\ 975 991 \end{description} … … 984 1000 coarse to have realistic melting or for studies where you need to control your heat and fw input.\\ 985 1001 986 A namelist parameters control over how many meters the heat and fw fluxes are spread. 987 \np{rn\_hisf\_tbl}] is the top boundary layer thickness as defined in \citet{Losch2008}. 1002 Two namelist parameters control how the heat and fw fluxes are passed to NEMO: \np{rn\_hisf\_tbl} and \np{ln\_divisf} 1003 \begin{description} 1004 \item[\np{rn\_hisf\_tbl}] is the top boundary layer thickness as defined in \citet{Losch2008}. 988 1005 This parameter is only used if \np{nn\_isf}~=~1 or \np{nn\_isf}~=~4 1006 It allows you to control over which depth you want to spread the heat and fw fluxes. 989 1007 990 1008 If \np{rn\_hisf\_tbl} = 0.0, the fluxes are put in the top level whatever is its tickness. 991 1009 992 If \np{rn\_hisf\_tbl} $>$ 0.0, the fluxes are spread over the first \np{rn\_hisf\_tbl} m (ie over one or several cells).\\ 993 994 The ice shelf melt is implemented as a volume flux with in the same way as for the runoff. 1010 If \np{rn\_hisf\_tbl} $>$ 0.0, the fluxes are spread over the first \np{rn\_hisf\_tbl} m (ie over one or several cells). 1011 1012 \item[\np{ln\_divisf}] is a flag to apply the fw flux as a volume flux or as a salt flux. 1013 1014 \np{ln\_divisf}~=~true applies the fwf as a volume flux. This volume flux is implemented with in the same way as for the runoff. 995 1015 The fw addition due to the ice shelf melting is, at each relevant depth level, added to the horizontal divergence 996 1016 (\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div}, called from \mdl{divcur}. 997 1017 See the runoff section \ref{SBC_rnf} for all the details about the divergence correction. 998 1018 999 1000 \section{ Ice sheet coupling} 1001 \label{SBC_iscpl} 1002 %------------------------------------------namsbc_iscpl---------------------------------------------------- 1003 \namdisplay{namsbc_iscpl} 1004 %-------------------------------------------------------------------------------------------------------- 1005 Ice sheet/ocean coupling is done through file exchange at the restart step. NEMO, at each restart step, 1006 read the bathymetry and ice shelf draft variable in a netcdf file. 1007 If \np{ln\_iscpl = ~true}, the isf draft is assume to be different at each restart step 1008 with potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics. 1009 The wetting and drying scheme applied on the restart is very simple and described below for the 6 different cases: 1010 \begin{description} 1011 \item[Thin a cell down:] 1012 T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant ($bt_b=bt_n$). 1013 \item[Enlarge a cell:] 1014 See case "Thin a cell down" 1015 \item[Dry a cell:] 1016 mask, T/S, U/V and ssh are set to 0. Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1017 \item[Wet a cell:] 1018 mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$ and U/V set to 0. If no neighbours along i,j and k, T/S/U/V and mask are set to 0. 1019 \item[Dry a column:] 1020 mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0. 1021 \item[Wet a column:] 1022 set mask to 1, T/S is extrapolated from neighbours, ssh is extrapolated from neighbours and U/V set to 0. If no neighbour, T/S/U/V and mask set to 0. 1019 \np{ln\_divisf}~=~false applies the fwf and heat flux directly on the salinity and temperature tendancy. 1020 1021 \item[\np{ln\_conserve}] is a flag for \np{nn\_isf}~=~1. A conservative boundary layer scheme as described in \citet{Jenkins2001} 1022 is used if \np{ln\_conserve}=true. It takes into account the fact that the melt water is at freezing T and needs to be warm up to ocean temperature. 1023 It is only relevant for \np{ln\_divisf}~=~false. 1024 If \np{ln\_divisf}~=~true, \np{ln\_conserve} has to be set to false to avoid a double counting of the contribution. 1025 1023 1026 \end{description} 1024 The extrapolation is call \np{nn\_drown} times. It means that if the grounding line retreat by more than \np{nn\_drown} cells between 2 coupling steps,1025 the code will be unable to fill all the new wet cells properly. The default number is set up for the MISOMIP idealised experiments.\\1026 This coupling procedure is able to take into account grounding line and calving front migration. However, it is a non-conservative processe.1027 This could lead to a trend in heat/salt content and volume. In order to remove the trend and keep the conservation level as close to 0 as possible,1028 a simple conservation scheme is available with \np{ln\_hsb = ~true}. The heat/salt/vol. gain/loss is diagnose, as well as the location.1029 Based on what is done on sbcrnf to prescribed a source of heat/salt/vol., the heat/salt/vol. gain/loss is removed/added,1030 over a period of \np{rn\_fiscpl} time step, into the system.1031 So after \np{rn\_fiscpl} time step, all the heat/salt/vol. gain/loss due to extrapolation process is canceled.\\1032 1033 As the before and now fields are not compatible (modification of the geometry), the restart time step is prescribed to be an euler time step instead of a leap frog and $fields_b = fields_n$.1034 1027 % 1035 1028 % ================================================================
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