Changeset 6140 for trunk/DOC/TexFiles/Chapters/Chap_SBC.tex
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- 2015-12-21T12:35:23+01:00 (8 years ago)
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trunk/DOC/TexFiles/Chapters/Chap_SBC.tex
r5120 r6140 49 49 (\np{nn\_ice}~=~0,1, 2 or 3); the addition of river runoffs as surface freshwater 50 50 fluxes or lateral inflow (\np{ln\_rnf}~=~true); the addition of isf melting as lateral inflow (parameterisation) 51 (\np{nn\_isf}~=~2 or 3 and \np{ln\_isfcav}~=~false) or as surface flux at the land-ice ocean interface 52 (\np{nn\_isf}~=~1 or 4 and \np{ln\_isfcav}~=~true); 51 or as surface flux at the land-ice ocean interface (\np{ln\_isf}=~true); 53 52 the addition of a freshwater flux adjustment in order to avoid a mean sea-level drift (\np{nn\_fwb}~=~0,~1~or~2); the 54 53 transformation of the solar radiation (if provided as daily mean) into a diurnal … … 958 957 \namdisplay{namsbc_isf} 959 958 %-------------------------------------------------------------------------------------------------------- 960 Namelist variable in \ngn{namsbc}, \np{nn\_isf}, 959 Namelist variable in \ngn{namsbc}, \np{nn\_isf}, control the kind of ice shelf representation used. 961 960 \begin{description} 962 961 \item[\np{nn\_isf}~=~1] 963 The ice shelf cavity is represented. The fwf and heat flux are computed. 962 The ice shelf cavity is represented. The fwf and heat flux are computed. 2 bulk formulations are available: the ISOMIP one (\np{nn\_isfblk = 1}) described in (\np{nn\_isfblk = 2}), the 3 equation formulation described in \citet{Jenkins1991}. In addition to this, 963 3 different way to compute the exchange coefficient are available. $\gamma\_{T/S}$ is constant (\np{nn\_gammablk = 0}), $\gamma\_{T/S}$ is velocity dependant \citep{Jenkins2010} (\np{nn\_gammablk = 1}) and $\gamma\_{T/S}$ is velocity dependant and stratification dependent \citep{Holland1999} (\np{nn\_gammablk = 2}). For each of them, the thermal/salt exchange coefficient (\np{rn\_gammat0} and \np{rn\_gammas0}) have to be specified (the default values are for the ISOMIP case). 964 964 Full description, sensitivity and validation in preparation. 965 965 … … 969 969 (\np{sn\_depmax\_isf}) and the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}) as in (\np{nn\_isf}~=~3). 970 970 Furthermore the fwf is computed using the \citet{Beckmann2003} parameterisation of isf melting. 971 The effective melting length (\np{sn\_Leff\_isf}) is read from a file .971 The effective melting length (\np{sn\_Leff\_isf}) is read from a file and the exchange coefficients are set as (\np{rn\_gammat0}) and (\np{rn\_gammas0}). 972 972 973 973 \item[\np{nn\_isf}~=~3] … … 987 987 \np{nn\_isf}~=~3 and \np{nn\_isf}~=~4 read the melt rate and heat flux from a file. You have total control of the fwf scenario. 988 988 989 989 This can be usefull if the water masses on the shelf are not realistic or the resolution (horizontal/vertical) are too 990 990 coarse to have realistic melting or for sensitivity studies where you want to control your input. 991 991 Full description, sensitivity and validation in preparation. 992 992 993 There is 2 ways to apply the fwf to NEMO. The first possibility (\np{ln\_divisf}~=~false) applied the fwf 994 and heat flux directly on the salinity and temperature tendancy. The second possibility (\np{ln\_divisf}~=~true) 995 apply the fwf as for the runoff fwf (see \S\ref{SBC_rnf}). The mass/volume addition due to the ice shelf melting is, 996 at each relevant depth level, added to the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div} 997 (called from \mdl{divcur}). 993 \np{rn\_hisf\_tbl} is the top boundary layer (tbl) thickness used by the Losch parametrisation \citep{Losch2008} to compute the melt. if 0, temperature/salt/velocity in the top cell is used to compute the melt. 994 Otherwise, NEMO used the mean value into the tbl. 995 996 \section{ Ice sheet coupling} 997 \label{SBC_iscpl} 998 %------------------------------------------namsbc_iscpl---------------------------------------------------- 999 \namdisplay{namsbc_iscpl} 1000 %-------------------------------------------------------------------------------------------------------- 1001 Ice sheet/ocean coupling is done through file exchange at the restart step. NEMO, at each restart step, 1002 read the bathymetry and ice shelf draft variable in a netcdf file. 1003 If \np{ln\_iscpl = ~true}, the isf draft is assume to be different at each restart step 1004 with potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics. 1005 The wetting and drying scheme applied on the restart is very simple and described below for the 6 different cases: 1006 \begin{description} 1007 \item[Thin a cell down:] 1008 T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant ($bt_b=bt_n$). 1009 \item[Enlarge a cell:] 1010 See case "Thin a cell down" 1011 \item[Dry a cell:] 1012 mask, T/S, U/V and ssh are set to 0. Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1013 \item[Wet a cell:] 1014 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. 1015 \item[Dry a column:] 1016 mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0. 1017 \item[Wet a column:] 1018 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 \end{description} 1020 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, 1021 the code will be unable to fill all the new wet cells properly. The default number is set up for the MISOMIP idealised experiments.\\ 1022 This coupling procedure is able to take into account grounding line and calving front migration. However, it is a non-conservative processe. 1023 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, 1024 a simple conservation scheme is available with \np{ln\_hsb = ~true}. The heat/salt/vol. gain/loss is diagnose, as well as the location. 1025 Based on what is done on sbcrnf to prescribed a source of heat/salt/vol., the heat/salt/vol. gain/loss is removed/added, 1026 over a period of \np{rn\_fiscpl} time step, into the system. 1027 So after \np{rn\_fiscpl} time step, all the heat/salt/vol. gain/loss due to extrapolation process is canceled.\\ 1028 1029 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 $fields_b = fields_n$. 998 1030 % 999 1031 % ================================================================
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