Changeset 11954 for NEMO/branches/2019/dev_r11613_ENHANCE-04_namelists_as_internalfiles/doc/latex/NEMO/subfiles/chap_SBC.tex
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- 2019-11-22T17:15:18+01:00 (4 years ago)
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NEMO/branches/2019/dev_r11613_ENHANCE-04_namelists_as_internalfiles/doc/latex/NEMO/subfiles/chap_SBC.tex
r11599 r11954 880 880 %ENDIF 881 881 882 %\gmcomment{ word doc of runoffs: 883 %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. 884 %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. 885 886 %The depth option makes it possible to have the river water affecting just the surface layer, throughout depth, or some specified point in between. 887 888 %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: 882 \cmtgm{ word doc of runoffs: 883 In the current \NEMO\ setup river runoff is added to emp fluxes, 884 these are then applied at just the sea surface as a volume change (in the variable volume case 885 this is a literal volume change, and in the linear free surface case the free surface is moved) 886 and a salt flux due to the concentration/dilution effect. 887 There is also an option to increase vertical mixing near river mouths; 888 this gives the effect of having a 3d river. 889 All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and 890 at the same temperature as the sea surface. 891 Our aim was to code the option to specify the temperature and salinity of river runoff, 892 (as well as the amount), along with the depth that the river water will affect. 893 This would make it possible to model low salinity outflow, such as the Baltic, 894 and would allow the ocean temperature to be affected by river runoff. 895 896 The depth option makes it possible to have the river water affecting just the surface layer, 897 throughout depth, or some specified point in between. 898 899 To do this we need to treat evaporation/precipitation fluxes and river runoff differently in 900 the \mdl{tra_sbc} module. 901 We decided to separate them throughout the code, 902 so that the variable emp represented solely evaporation minus precipitation fluxes, 903 and a new 2d variable rnf was added which represents the volume flux of river runoff 904 (in $kg/m^2s$ to remain consistent with $emp$). 905 This meant many uses of emp and emps needed to be changed, 906 a list of all modules which use $emp$ or $emps$ and the changes made are below:} 889 907 890 908 %% ================================================================================================= … … 908 926 Two different bulk formulae are available: 909 927 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 928 \begin{description} 929 \item [{\np[=1]{nn_isfblk}{nn\_isfblk}}]: The melt rate is based on a balance between the upward ocean heat flux and 930 the latent heat flux at the ice shelf base. A complete description is available in \citet{hunter_rpt06}. 931 \item [{\np[=2]{nn_isfblk}{nn\_isfblk}}]: The melt rate and the heat flux are based on a 3 equations formulation 932 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 933 A complete description is available in \citet{jenkins_JGR91}. 934 \end{description} 935 936 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 937 Its thickness is defined by \np{rn_hisf_tbl}{rn\_hisf\_tbl}. 938 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn_hisf_tbl}{rn\_hisf\_tbl} m. 939 Then, the fluxes are spread over the same thickness (ie over one or several cells). 940 If \np{rn_hisf_tbl}{rn\_hisf\_tbl} larger than top $e_{3}t$, there is no more feedback between the freezing point at the interface and the the top cell temperature. 941 This can lead to super-cool temperature in the top cell under melting condition. 942 If \np{rn_hisf_tbl}{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 943 944 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 945 There are 3 different ways to compute the exchange coeficient: 946 \begin{description} 947 \item [{\np[=0]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are constant and defined by \np{rn_gammas0}{rn\_gammas0} and \np{rn_gammat0}{rn\_gammat0}. 948 \begin{gather*} 931 949 % \label{eq:SBC_isf_gamma_iso} 932 933 934 935 936 937 938 939 940 941 942 943 944 \[945 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}}946 \]947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 As in \np[=1]{nn_isf}{nn\_isf}, the fluxes are spread over the top boundary layer thickness (\np{rn_hisf_tbl}{rn\_hisf\_tbl})\\950 \gamma^{T} = rn\_gammat0 \\ 951 \gamma^{S} = rn\_gammas0 952 \end{gather*} 953 This is the recommended formulation for ISOMIP. 954 \item [{\np[=1]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity dependent and defined as 955 \begin{gather*} 956 \gamma^{T} = rn\_gammat0 \times u_{*} \\ 957 \gamma^{S} = rn\_gammas0 \times u_{*} 958 \end{gather*} 959 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters). 960 See \citet{jenkins.nicholls.ea_JPO10} for all the details on this formulation. It is the recommended formulation for realistic application. 961 \item [{\np[=2]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity and stability dependent and defined as: 962 \[ 963 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 964 \] 965 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters), 966 $\Gamma_{Turb}$ the contribution of the ocean stability and 967 $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 968 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 969 This formulation has not been extensively tested in \NEMO\ (not recommended). 970 \end{description} 971 \item [{\np[=2]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 972 The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 973 The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 974 (\np{sn_depmax_isf}{sn\_depmax\_isf}) and the base of the ice shelf along the calving front 975 (\np{sn_depmin_isf}{sn\_depmin\_isf}) as in (\np[=3]{nn_isf}{nn\_isf}). 976 The effective melting length (\np{sn_Leff_isf}{sn\_Leff\_isf}) is read from a file. 977 \item [{\np[=3]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 978 The fwf (\np{sn_rnfisf}{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between 979 the depth of the average grounding line (GL) (\np{sn_depmax_isf}{sn\_depmax\_isf}) and 980 the base of the ice shelf along the calving front (\np{sn_depmin_isf}{sn\_depmin\_isf}). 981 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 982 \item [{\np[=4]{nn_isf}{nn\_isf}}]: The ice shelf cavity is opened (\np[=.true.]{ln_isfcav}{ln\_isfcav} needed). 983 However, the fwf is not computed but specified from file \np{sn_fwfisf}{sn\_fwfisf}). 984 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 985 As in \np[=1]{nn_isf}{nn\_isf}, the fluxes are spread over the top boundary layer thickness (\np{rn_hisf_tbl}{rn\_hisf\_tbl}) 968 986 \end{description} 969 987 … … 986 1004 \begin{figure}[!t] 987 1005 \centering 988 \includegraphics[width=0.66\textwidth]{ Fig_SBC_isf}1006 \includegraphics[width=0.66\textwidth]{SBC_isf} 989 1007 \caption[Ice shelf location and fresh water flux definition]{ 990 1008 Illustration of the location where the fwf is injected and … … 1307 1325 \begin{figure}[!t] 1308 1326 \centering 1309 \includegraphics[width=0.66\textwidth]{ Fig_SBC_diurnal}1327 \includegraphics[width=0.66\textwidth]{SBC_diurnal} 1310 1328 \caption[Reconstruction of the diurnal cycle variation of short wave flux]{ 1311 1329 Example of reconstruction of the diurnal cycle variation of short wave flux from … … 1341 1359 \begin{figure}[!t] 1342 1360 \centering 1343 \includegraphics[width=0.66\textwidth]{ Fig_SBC_dcy}1361 \includegraphics[width=0.66\textwidth]{SBC_dcy} 1344 1362 \caption[Reconstruction of the diurnal cycle variation of short wave flux on an ORCA2 grid]{ 1345 1363 Example of reconstruction of the diurnal cycle variation of short wave flux from … … 1521 1539 % in ocean-ice models. 1522 1540 1523 \ onlyinsubfile{\input{../../global/epilogue}}1541 \subinc{\input{../../global/epilogue}} 1524 1542 1525 1543 \end{document}
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