Changeset 6317 for branches/2015/nemo_v3_6_STABLE/DOC/TexFiles/Chapters/Chap_SBC.tex

Timestamp:

2016-02-15T16:21:15+01:00 (8 years ago)

Author:

mathiot

Message:

ISF: update documentation and biblio

File:

• branches/2015/nemo_v3_6_STABLE/DOC/TexFiles/Chapters/Chap_SBC.tex (modified) (2 diffs)

branches/2015/nemo_v3_6_STABLE/DOC/TexFiles/Chapters/Chap_SBC.tex

@@ -924 +924 @@
 \namdisplay{namsbc_isf}
 %--------------------------------------------------------------------------------------------------------
-Namelist variable in \ngn{namsbc}, \np{nn\_isf}, control the kind of ice shelf representation used. 
+Namelist variable in \ngn{namsbc}, \np{nn\_isf}, controls the ice shelf representation used. 
 \begin{description}
 \item[\np{nn\_isf}~=~1]
-The ice shelf cavity is represented. The fwf and heat flux are computed. 
-Full description, sensitivity and validation in preparation. 
+The ice shelf cavity is represented. The fwf and heat flux are computed. Two different bulk formula are available:
+   \begin{description}
+   \item[\np{nn\_isfblk}~=~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}~=~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).
+   \end{description}
+
+For this 2 bulk formulations, there are 3 different ways to compute the exchange coeficient:
+   \begin{description}
+        \item[\np{nn\_gammablk~=~0~}]
+   The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0}
+
+   \item[\np{nn\_gammablk~=~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~=~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.
+        \end{description}
 
 \item[\np{nn\_isf}~=~2]
@@ -934 +961 @@
 The fwf is 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}~=~3). 
-Furthermore the fwf is computed using the \citet{Beckmann2003} parameterisation of isf melting. 
+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}~=~3]
 A simple parameterisation of isf is used. The ice shelf cavity is not represented. 
-The fwf (\np{sn\_rnfisf}) is 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}).
-Full description, sensitivity and validation in preparation.
+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}~=~4]
-The ice shelf cavity is represented. However, the fwf (\np{sn\_fwfisf}) and heat flux (\np{sn\_qisf}) are 
-not computed but specified from file. 
+The ice shelf cavity is opened. However, the fwf is not computed but specified from file \np{sn\_fwfisf}). 
+The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$.\\
 \end{description}
 
-\np{nn\_isf}~=~1 and \np{nn\_isf}~=~2 compute a melt rate based on the water masse properties, ocean velocities and depth.
- This flux is thus highly dependent of the model resolution (horizontal and vertical), realism of the water masse onto the shelf ...
-
-\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.
-
+
+$\bullet$ \np{nn\_isf}~=~1 and \np{nn\_isf}~=~2 compute a melt rate based on the water mass properties, ocean velocities and depth.
+ This flux is thus highly dependent of the model resolution (horizontal and vertical), realism of the water masses onto the shelf ...\\
+
+
+$\bullet$ \np{nn\_isf}~=~3 and \np{nn\_isf}~=~4 read the melt rate from a file. You have total control of the fwf forcing.
 This can be usefull if the water masses on the shelf are not realistic or the resolution (horizontal/vertical) are too 
-coarse to have realistic melting or for sensitivity studies where you want to control your input. 
-Full description, sensitivity and validation in preparation. 
-
-There is 2 ways to apply the fwf to NEMO. The first possibility (\np{ln\_divisf}~=~false) applied the fwf
- and heat flux directly on the salinity and temperature tendancy. The second possibility (\np{ln\_divisf}~=~true)
- apply the fwf as for the runoff fwf (see \S\ref{SBC_rnf}). The mass/volume 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}). 
+coarse to have realistic melting or for studies where you need to control your heat and fw input.\\ 
+
+Two namelist parameters control how the heat and fw fluxes are passed to NEMO: \np{rn\_hisf\_tbl} and \np{ln\_divisf}
+\begin{description}
+\item[\np{rn\_hisf\_tbl}] is the top boundary layer thickness as defined in \citet{Losch2008}. 
+This parameter is only used if \np{nn\_isf}~=~1 or \np{nn\_isf}~=~4
+It allows you to control over which depth you want to spread the heat and fw fluxes. 
+
+If \np{rn\_hisf\_tbl} = 0.0, the fluxes are put in the top level whatever is its tickness. 
+
+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).
+
+\item[\np{ln\_divisf}] is a flag to apply the fw flux as a volume flux or as a salt flux. 
+
+\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.
+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 \ref{SBC_rnf} for all the details about the divergence correction. 
+
+\np{ln\_divisf}~=~false applies the fwf and heat flux directly on the salinity and temperature tendancy.
+
+\item[\np{ln\_conserve}] is a flag for \np{nn\_isf}~=~1. A conservative boundary layer scheme as described in \citet{Jenkins2001} 
+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. 
+It is only relevant for \np{ln\_divisf}~=~false. 
+If \np{ln\_divisf}~=~true, \np{ln\_conserve} has to be set to false to avoid a double counting of the contribution. 
+ 
+\end{description}
 %
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