Changeset 10468

Timestamp:

2019-01-08T12:34:39+01:00 (6 years ago)

Author:

mathiot

Message:

update ISF documentation (DYN and SBC)

Location:

NEMO/trunk/doc/latex/NEMO

Files:

• main/NEMO_manual.bib (modified) (2 diffs)
• subfiles/chap_DYN.tex (modified) (2 diffs)
• subfiles/chap_SBC.tex (modified) (4 diffs)

NEMO/trunk/doc/latex/NEMO/main/NEMO_manual.bib

@@ -1062 +1062 @@
    S. Alonso, D. Gomis, A. Viudez, M. Astraldi, D. Bacciola, M. Borghini,
    F. Dell'amico, C. Galli, E. Lazzoni, G. P. Gasparini, S. Sparnocchia,
-   and A. Harzallah, 1995 : Progress from 1989 to 1992 in understanding
-   the circulation of the Western Mediterranean Sea. Oceanologica Acta,
-   18, 2, 255-271.},
-  title = {EUROMODEL Group (P.M. Lehucher, L. Beautier, M. Chartier, F. Martel,
-   L. Mortier, P. Brehmer, C. Millot, C. Alberola, M. Benzhora, I. Taupier-Letage,
-   G. Chabert d'Hieres, H. Didelle, P. Gleizon, D. Obaton, M. Cr\'{e}pon,
-   C. Herbaut, G. Madec, S. Speich, J. Nihoul, J. M. Beckers, P. Brasseur,
-   E. Deleersnijder, S. Djenidi, J. Font, A. Castellon, E. Garcia-Ladona,
-   M. J. Lopez-Garcia, M. Manriquez, M. Maso, J. Salat, J. Tintore,
-   S. Alonso, D. Gomis, A. Viudez, M. Astraldi, D. Bacciola, M. Borghini,
-   F. Dell'amico, C. Galli, E. Lazzoni, G. P. Gasparini, S. Sparnocchia,
-   and A. Harzallah, 1995 : Progress from 1989 to 1992 in understanding
-   the circulation of the Western Mediterranean Sea.},
+   and A. Harzallah)},
+  title = {Progress from 1989 to 1992 in understanding the circulation of the Western Mediterranean Sea.},
   journal = {Oceanologica Acta},
   year = {1995},
@@ -2434 +2423 @@
   pages = {L07703},
   doi = {10.1029/2004GL021980},
+}
+
+@Article{Mathiot2017,
+AUTHOR = {Mathiot, P. and Jenkins, A. and Harris, C. and Madec, G.},
+TITLE = {Explicit representation and parametrised impacts of under ice shelf seas in the ${z}^{\ast}$ coordinate ocean model NEMO 3.6},
+JOURNAL = {Geoscientific Model Development},
+VOLUME = {10},
+YEAR = {2017},
+NUMBER = {7},
+PAGES = {2849--2874},
+URL = {https://www.geosci-model-dev.net/10/2849/2017/},
+DOI = {10.5194/gmd-10-2849-2017}
 }
 

NEMO/trunk/doc/latex/NEMO/subfiles/chap_DYN.tex

@@ -697 +697 @@
 \label{subsec:DYN_hpg_isf}
 Beneath an ice shelf, the total pressure gradient is the sum of the pressure gradient due to the ice shelf load and
-the pressure gradient due to the ocean load.
-If cavity opened (\np{ln\_isfcav}\forcode{ = .true.}) these 2 terms can be calculated by
-setting \np{ln\_dynhpg\_isf}\forcode{ = .true.}.
-No other scheme are working with the ice shelf.\\
-
-$\bullet$ The main hypothesis to compute the ice shelf load is that the ice shelf is in an isostatic equilibrium.
+the pressure gradient due to the ocean load (\np{ln\_dynhpg\_isf}\forcode{ = .true.}).\\
+
+The main hypothesis to compute the ice shelf load is that the ice shelf is in an isostatic equilibrium.
 The top pressure is computed integrating from surface to the base of the ice shelf a reference density profile
 (prescribed as density of a water at 34.4 PSU and -1.9\deg{C}) and
@@ -709 +706 @@
 A detailed description of this method is described in \citet{Losch2008}.\\
 
-$\bullet$ The ocean load is computed using the expression \autoref{eq:dynhpg_sco} described in
+The pressure gradient due to ocean load is computed using the expression \autoref{eq:dynhpg_sco} described in
 \autoref{subsec:DYN_hpg_sco}. 
 

NEMO/trunk/doc/latex/NEMO/subfiles/chap_SBC.tex

@@ -921 +921 @@
 
 The mass/volume addition due to the river runoff is, at each relevant depth level, added to
-the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_rnf\_div} (called from \mdl{divcur}).
+the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_rnf\_div} (called from \mdl{divhor}).
 This increases the diffusion term in the vicinity of the river, thereby simulating a momentum flux.
 The sea surface height is calculated using the sum of the horizontal divergence terms,
@@ -990 +990 @@
 \nlst{namsbc_isf}
 %--------------------------------------------------------------------------------------------------------
-Namelist variable in \ngn{namsbc}, \np{nn\_isf}, controls the ice shelf representation used. 
+The namelist variable in \ngn{namsbc}, \np{nn\_isf}, controls the ice shelf representation.
+Description and result of sensitivity test to \np{nn\_isf} are presented in \citet{Mathiot2017}. 
+The different options are illustrated in \autoref{fig:SBC_isf}.
+
 \begin{description}
-\item[\np{nn\_isf}\forcode{ = 1}]
+\item[\np{nn\_isf}\forcode{ = 1}]:
   The ice shelf cavity is represented (\np{ln\_isfcav}\forcode{ = .true.} needed).
-  The fwf and heat flux are computed.
-  Two different bulk formula are available:
+  The fwf and heat flux are depending of the local water properties.
+  Two different bulk formulae are available:
+
    \begin{description}
-   \item[\np{nn\_isfblk}\forcode{ = 1}]
-     The bulk formula used to compute the melt is based the one described in \citet{Hunter2006}.
-     This formulation is based on a balance between the upward ocean heat flux and
-     the latent heat flux at the ice shelf base.
-   \item[\np{nn\_isfblk}\forcode{ = 2}]
-     The bulk formula used to compute the melt is based the one described in \citet{Jenkins1991}.
-     This formulation is based on a 3 equations formulation
-     (a heat flux budget, a salt flux budget and a linearised freezing point temperature equation).
+   \item[\np{nn\_isfblk}\forcode{ = 1}]:
+     The melt rate is based on a balance between the upward ocean heat flux and
+     the latent heat flux at the ice shelf base. A complete description is available in \citet{Hunter2006}.
+   \item[\np{nn\_isfblk}\forcode{ = 2}]:
+     The melt rate and the heat flux are based on a 3 equations formulation
+     (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 
+     A complete description is available in \citet{Jenkins1991}.
    \end{description}
-   For this 2 bulk formulations, there are 3 different ways to compute the exchange coeficient:
+
+     Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{Losch2008}. 
+     Its thickness is defined by \np{rn\_hisf\_tbl}.
+     The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn\_hisf\_tbl} m.
+     Then, the fluxes are spread over the same thickness (ie over one or several cells).
+     If \np{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.
+     This can lead to super-cool temperature in the top cell under melting condition.
+     If \np{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\
+
+     Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 
+     There are 3 different ways to compute the exchange coeficient:
    \begin{description}
-   \item[\np{nn\_gammablk}\forcode{ = 0}]
-     The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}
-   \item[\np{nn\_gammablk}\forcode{ = 1}]
+        \item[\np{nn\_gammablk}\forcode{ = 0}]:
+     The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}. 
+\[
+  % \label{eq:sbc_isf_gamma_iso}
+\gamma^{T} = \np{rn\_gammat0}
+\]
+\[
+\gamma^{S} = \np{rn\_gammas0}
+\]
+     This is the recommended formulation for ISOMIP.
+   \item[\np{nn\_gammablk}\forcode{ = 1}]:
      The salt and heat exchange coefficients are velocity dependent and defined as
-     \np{rn\_gammas0}$ \times u_{*}$ and \np{rn\_gammat0}$ \times u_{*}$ where
-     $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters).
-     See \citet{Jenkins2010} for all the details on this formulation.
-   \item[\np{nn\_gammablk}\forcode{ = 2}]
-     The salt and heat exchange coefficients are velocity and stability dependent and defined as
-     $\gamma_{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}}$ where
-     $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters),
+\[
+\gamma^{T} = \np{rn\_gammat0} \times u_{*} 
+\]
+\[
+\gamma^{S} = \np{rn\_gammas0} \times u_{*}
+\]
+     where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters).
+     See \citet{Jenkins2010} for all the details on this formulation. It is the recommended formulation for realistic application.
+   \item[\np{nn\_gammablk}\forcode{ = 2}]:
+     The salt and heat exchange coefficients are velocity and stability dependent and defined as:
+\[
+\gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 
+\]
+     where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters),
      $\Gamma_{Turb}$ the contribution of the ocean stability and
      $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion.
-     See \citet{Holland1999} for all the details on this formulation.
+     See \citet{Holland1999} for all the details on this formulation. 
+     This formulation has not been extensively tested in NEMO (not recommended).
    \end{description}
- \item[\np{nn\_isf}\forcode{ = 2}]
-   A parameterisation of isf is used. The ice shelf cavity is not represented.
-   The fwf is distributed along the ice shelf edge between the depth of the average grounding line (GL)
+ \item[\np{nn\_isf}\forcode{ = 2}]:
+   The ice shelf cavity is not represented.
+   The fwf and heat flux are computed using the \citet{Beckmann2003} parameterisation of isf melting.
+   The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL)
    (\np{sn\_depmax\_isf}) and the base of the ice shelf along the calving front
    (\np{sn\_depmin\_isf}) as in (\np{nn\_isf}\forcode{ = 3}).
-   Furthermore the fwf and heat flux are computed using the \citet{Beckmann2003} parameterisation of isf melting.
    The effective melting length (\np{sn\_Leff\_isf}) is read from a file.
- \item[\np{nn\_isf}\forcode{ = 3}]
-   A simple parameterisation of isf is used. The ice shelf cavity is not represented.
+ \item[\np{nn\_isf}\forcode{ = 3}]:
+   The ice shelf cavity is not represented.
    The fwf (\np{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between
    the depth of the average grounding line (GL) (\np{sn\_depmax\_isf}) and
    the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}).
    The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$.
- \item[\np{nn\_isf}\forcode{ = 4}]
+ \item[\np{nn\_isf}\forcode{ = 4}]:
    The ice shelf cavity is opened (\np{ln\_isfcav}\forcode{ = .true.} needed).
    However, the fwf is not computed but specified from file \np{sn\_fwfisf}).
-   The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$.\\
+   The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$.
+   As in \np{nn\_isf}\forcode{ = 1}, the fluxes are spread over the top boundary layer thickness (\np{rn\_hisf\_tbl})\\
 \end{description}
 
@@ -1053 +1083 @@
 for studies where you need to control your heat and fw input.\\ 
 
-A namelist parameters control over how many meters the heat and fw fluxes are spread.
-\np{rn\_hisf\_tbl}] is the top boundary layer thickness as defined in \citet{Losch2008}.
-This parameter is only used if \np{nn\_isf}\forcode{ = 1} or \np{nn\_isf}\forcode{ = 4}.
-
-If \np{rn\_hisf\_tbl}\forcode{ = 0}., the fluxes are put in the top level whatever is its tickness. 
-
-If \np{rn\_hisf\_tbl} $>$ 0., the fluxes are spread over the first \np{rn\_hisf\_tbl} m
-(ie over one or several cells).\\
-
-The ice shelf melt is implemented as a volume flux with in the same way as for the runoff.
+The ice shelf melt is implemented as a volume flux as for the runoff.
 The fw addition due to the ice shelf melting is, at each relevant depth level, added to
-the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div}, called from \mdl{divcur}.
-See the runoff section \autoref{sec:SBC_rnf} for all the details about the divergence correction.
-
+the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div}, called from \mdl{divhor}.
+See the runoff section \autoref{sec:SBC_rnf} for all the details about the divergence correction.\\
+
+%>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+\begin{figure}[!t]
+  \begin{center}
+    \includegraphics[width=0.8\textwidth]{Fig_SBC_isf}
+    \caption{
+      \protect\label{fig:SBC_isf}
+      Illustration the location where the fwf is injected and whether or not the fwf is interactif or not depending of \np{nn\_isf}.
+    }
+  \end{center}
+\end{figure}
+%>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
 \section{Ice sheet coupling}
@@ -1075 +1107 @@
 %--------------------------------------------------------------------------------------------------------
 Ice sheet/ocean coupling is done through file exchange at the restart step.
-NEMO, at each restart step, read the bathymetry and ice shelf draft variable in a netcdf file.
+At each restart step:
+\begin{description}
+\item[Step 1]: the ice sheet model send a new bathymetry and ice shelf draft netcdf file.
+\item[Step 2]: a new domcfg.nc file is built using the DOMAINcfg tools.
+\item[Step 3]: NEMO run for a specific period and output the average melt rate over the period.
+\item[Step 4]: the ice sheet model run using the melt rate outputed in step 4.
+\item[Step 5]: go back to 1.
+\end{description}
+
 If \np{ln\_iscpl}\forcode{ = .true.}, the isf draft is assume to be different at each restart step with
 potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics.
-The wetting and drying scheme applied on the restart is very simple and described below for the 6 different cases:
+The wetting and drying scheme applied on the restart is very simple and described below for the 6 different possible cases:
 \begin{description}
-\item[Thin a cell down:]
+\item[Thin a cell down]:
   T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant
   ($bt_b=bt_n$).
-\item[Enlarge  a cell:]
+\item[Enlarge  a cell]:
   See case "Thin a cell down"
-\item[Dry a cell:]
+\item[Dry a cell]:
   mask, T/S, U/V and ssh are set to 0.
   Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$).
-\item[Wet a cell:] 
+\item[Wet a cell]: 
   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.
-\item[Dry a column:]
+  If no neighbours, T/S is extrapolated from old top cell value. 
+  If no neighbours along i,j and k (both previous test failed), T/S/U/V/ssh and mask are set to 0.
+\item[Dry a column]:
    mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0.
-\item[Wet a column:]
+\item[Wet a column]:
   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.
 \end{description}
-The extrapolation is call \np{nn\_drown} times.
+
+Furthermore, 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 $fields_b = fields_n$.\\
+
+The horizontal extrapolation to fill new cell with realistic value is called \np{nn\_drown} times.
 It means that if the grounding line retreat by more than \np{nn\_drown} cells between 2 coupling steps,
 the code will be unable to fill all the new wet cells properly.
-The default number is set up for the MISOMIP idealised experiments.\\
+The default number is set up for the MISOMIP idealised experiments.
 This coupling procedure is able to take into account grounding line and calving front migration.
 However, it is a non-conservative processe. 
-This could lead to a trend in heat/salt content and volume.
+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,
 a simple conservation scheme is available with \np{ln\_hsb}\forcode{ = .true.}.
-The heat/salt/vol. gain/loss is diagnose, as well as the location.
-Based on what is done on sbcrnf to prescribed a source of heat/salt/vol.,
-the heat/salt/vol. gain/loss is removed/added, over a period of \np{rn\_fiscpl} time step, into the system. 
-So after \np{rn\_fiscpl} time step, all the heat/salt/vol. gain/loss due to extrapolation process is canceled.\\
-
-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 $fields_b = fields_n$.
+The heat/salt/vol. gain/loss is diagnosed, as well as the location.
+A correction increment is computed and apply each time step during the next \np{rn\_fiscpl} time steps. 
+For safety, it is advised to set \np{rn\_fiscpl} equal to the coupling period (smallest increment possible).
+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).
+
 %
 % ================================================================