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Changeset 11954 for NEMO/branches/2019/dev_r11613_ENHANCE-04_namelists_as_internalfiles/doc/latex/NEMO/subfiles/chap_SBC.tex – NEMO

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Timestamp:
2019-11-22T17:15:18+01:00 (4 years ago)
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acc
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Branch 2019/dev_r11613_ENHANCE-04_namelists_as_internalfiles. Merge in trunk changes up to 11943 in preparation for end of year merge

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  • NEMO/branches/2019/dev_r11613_ENHANCE-04_namelists_as_internalfiles/doc/latex/NEMO/subfiles/chap_SBC.tex

    r11599 r11954  
    880880%ENDIF 
    881881 
    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: 
     883In the current \NEMO\ setup river runoff is added to emp fluxes, 
     884these are then applied at just the sea surface as a volume change (in the variable volume case 
     885this is a literal volume change, and in the linear free surface case the free surface is moved) 
     886and a salt flux due to the concentration/dilution effect. 
     887There is also an option to increase vertical mixing near river mouths; 
     888this gives the effect of having a 3d river. 
     889All river runoff and emp fluxes are assumed to be fresh water (zero salinity) and 
     890at the same temperature as the sea surface. 
     891Our 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. 
     893This would make it possible to model low salinity outflow, such as the Baltic, 
     894and would allow the ocean temperature to be affected by river runoff. 
     895 
     896The depth option makes it possible to have the river water affecting just the surface layer, 
     897throughout depth, or some specified point in between. 
     898 
     899To do this we need to treat evaporation/precipitation fluxes and river runoff differently in 
     900the \mdl{tra_sbc} module. 
     901We decided to separate them throughout the code, 
     902so that the variable emp represented solely evaporation minus precipitation fluxes, 
     903and a new 2d variable rnf was added which represents the volume flux of river runoff 
     904(in $kg/m^2s$ to remain consistent with $emp$). 
     905This meant many uses of emp and emps needed to be changed, 
     906a list of all modules which use $emp$ or $emps$ and the changes made are below:} 
    889907 
    890908%% ================================================================================================= 
     
    908926  Two different bulk formulae are available: 
    909927 
    910    \begin{description} 
    911    \item [{\np[=1]{nn_isfblk}{nn\_isfblk}}]: The melt rate is based on a balance between the upward ocean heat flux and 
    912      the latent heat flux at the ice shelf base. A complete description is available in \citet{hunter_rpt06}. 
    913    \item [{\np[=2]{nn_isfblk}{nn\_isfblk}}]: The melt rate and the heat flux are based on a 3 equations formulation 
    914      (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 
    915      A complete description is available in \citet{jenkins_JGR91}. 
    916    \end{description} 
    917  
    918      Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 
    919      Its thickness is defined by \np{rn_hisf_tbl}{rn\_hisf\_tbl}. 
    920      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. 
    921      Then, the fluxes are spread over the same thickness (ie over one or several cells). 
    922      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. 
    923      This can lead to super-cool temperature in the top cell under melting condition. 
    924      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.\\ 
    925  
    926      Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 
    927      There are 3 different ways to compute the exchange coeficient: 
    928    \begin{description} 
    929         \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}. 
    930      \begin{gather*} 
     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*} 
    931949       % \label{eq:SBC_isf_gamma_iso} 
    932        \gamma^{T} = rn\_gammat0 \\ 
    933        \gamma^{S} = rn\_gammas0 
    934      \end{gather*} 
    935      This is the recommended formulation for ISOMIP. 
    936    \item [{\np[=1]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity dependent and defined as 
    937      \begin{gather*} 
    938        \gamma^{T} = rn\_gammat0 \times u_{*} \\ 
    939        \gamma^{S} = rn\_gammas0 \times u_{*} 
    940      \end{gather*} 
    941      where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters). 
    942      See \citet{jenkins.nicholls.ea_JPO10} for all the details on this formulation. It is the recommended formulation for realistic application. 
    943    \item [{\np[=2]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity and stability dependent and defined as: 
    944 \[ 
    945 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 
    946 \] 
    947      where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters), 
    948      $\Gamma_{Turb}$ the contribution of the ocean stability and 
    949      $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 
    950      See \citet{holland.jenkins_JPO99} for all the details on this formulation. 
    951      This formulation has not been extensively tested in \NEMO\ (not recommended). 
    952    \end{description} 
    953   \item [{\np[=2]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 
    954    The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 
    955    The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 
    956    (\np{sn_depmax_isf}{sn\_depmax\_isf}) and the base of the ice shelf along the calving front 
    957    (\np{sn_depmin_isf}{sn\_depmin\_isf}) as in (\np[=3]{nn_isf}{nn\_isf}). 
    958    The effective melting length (\np{sn_Leff_isf}{sn\_Leff\_isf}) is read from a file. 
    959   \item [{\np[=3]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 
    960    The fwf (\np{sn_rnfisf}{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between 
    961    the depth of the average grounding line (GL) (\np{sn_depmax_isf}{sn\_depmax\_isf}) and 
    962    the base of the ice shelf along the calving front (\np{sn_depmin_isf}{sn\_depmin\_isf}). 
    963    The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 
    964   \item [{\np[=4]{nn_isf}{nn\_isf}}]: The ice shelf cavity is opened (\np[=.true.]{ln_isfcav}{ln\_isfcav} needed). 
    965    However, the fwf is not computed but specified from file \np{sn_fwfisf}{sn\_fwfisf}). 
    966    The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 
    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}) 
    968986\end{description} 
    969987 
     
    9861004\begin{figure}[!t] 
    9871005  \centering 
    988   \includegraphics[width=0.66\textwidth]{Fig_SBC_isf} 
     1006  \includegraphics[width=0.66\textwidth]{SBC_isf} 
    9891007  \caption[Ice shelf location and fresh water flux definition]{ 
    9901008    Illustration of the location where the fwf is injected and 
     
    13071325\begin{figure}[!t] 
    13081326  \centering 
    1309   \includegraphics[width=0.66\textwidth]{Fig_SBC_diurnal} 
     1327  \includegraphics[width=0.66\textwidth]{SBC_diurnal} 
    13101328  \caption[Reconstruction of the diurnal cycle variation of short wave flux]{ 
    13111329    Example of reconstruction of the diurnal cycle variation of short wave flux from 
     
    13411359\begin{figure}[!t] 
    13421360  \centering 
    1343   \includegraphics[width=0.66\textwidth]{Fig_SBC_dcy} 
     1361  \includegraphics[width=0.66\textwidth]{SBC_dcy} 
    13441362  \caption[Reconstruction of the diurnal cycle variation of short wave flux on an ORCA2 grid]{ 
    13451363    Example of reconstruction of the diurnal cycle variation of short wave flux from 
     
    15211539% in ocean-ice models. 
    15221540 
    1523 \onlyinsubfile{\input{../../global/epilogue}} 
     1541\subinc{\input{../../global/epilogue}} 
    15241542 
    15251543\end{document} 
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