Changeset 3267 for branches/2011/dev_NEMO_MERGE_2011/DOC/TexFiles/Chapters/Chap_LDF.tex

Timestamp:

2012-01-18T11:28:11+01:00 (12 years ago)

Author:

agn

Message:

dev_NEMO_MERGE_2011:(DOC) Finish griffies description, remove need for pstricks

File:

• branches/2011/dev_NEMO_MERGE_2011/DOC/TexFiles/Chapters/Chap_LDF.tex (modified) (4 diffs)

branches/2011/dev_NEMO_MERGE_2011/DOC/TexFiles/Chapters/Chap_LDF.tex

@@ -21 +21 @@
 and for tracers only, eddy induced advection on tracers). These three aspects 
 of the lateral diffusion are set through namelist parameters and CPP keys 
-(see the \textit{nam\_traldf} and \textit{nam\_dynldf} below).
+(see the \textit{nam\_traldf} and \textit{nam\_dynldf} below). Note
+that this chapter describes the default implementation of iso-neutral
+tracer mixing, and Griffies's implementation, which is used if
+\np{traldf\_grif}=true, is described in Appdx\ref{sec:triad}
 
 %-----------------------------------nam_traldf - nam_dynldf--------------------------------------------
@@ -128 +131 @@
 $\ $\newline    % force a new ligne
 
-A space variation in the eddy coefficient appeals several remarks:
+The following points are relevant when the eddy coefficient varies spatially:
 
 (1) the momentum diffusion operator acting along model level surfaces is 
 written in terms of curl and divergent components of the horizontal current 
-(see \S\ref{PE_ldf}). Although the eddy coefficient can be set to different values 
-in these two terms, this option is not available. 
+(see \S\ref{PE_ldf}). Although the eddy coefficient could be set to different values 
+in these two terms, this option is not currently available. 
 
 (2) with an horizontally varying viscosity, the quadratic integral constraints 
@@ -275 +278 @@
 
 \item[$s$- or hybrid $s$-$z$- coordinate : ] in the current release of \NEMO, 
-there is no specific treatment for iso-neutral mixing in the $s$-coordinate. 
+iso-neutral mixing is only employed for $s$-coordinates if the
+Griffies scheme is used (\np{traldf\_grif}=true; see Appdx \ref{sec:triad}). 
 In other words, iso-neutral mixing will only be accurately represented with a 
 linear equation of state (\np{nn\_eos}=1 or 2). In the case of a "true" equation 
@@ -332 +336 @@
 \end{description}
 
-This implementation is a rather old one. It is similar to the one proposed 
-by Cox [1987], except for the background horizontal diffusion. Indeed, 
-the Cox implementation of isopycnal diffusion in GFDL-type models requires 
-a minimum background horizontal diffusion for numerical stability reasons. 
-To overcome this problem, several techniques have been proposed in which 
-the numerical schemes of the ocean model are modified \citep{Weaver_Eby_JPO97, 
-Griffies_al_JPO98}. Here, another strategy has been chosen \citep{Lazar_PhD97}: 
-a local filtering of the iso-neutral slopes (made on 9 grid-points) prevents 
-the development of grid point noise generated by the iso-neutral diffusion 
-operator (Fig.~\ref{Fig_LDF_ZDF1}). This allows an iso-neutral diffusion scheme 
-without additional background horizontal mixing. This technique can be viewed 
-as a diffusion operator that acts along large-scale (2~$\Delta$x) 
-\gmcomment{2deltax doesnt seem very large scale} 
-iso-neutral surfaces. The diapycnal diffusion required for numerical stability is 
-thus minimized and its net effect on the flow is quite small when compared to 
-the effect of an horizontal background mixing. 
+This implementation is a rather old one. It is similar to the one
+proposed by Cox [1987], except for the background horizontal
+diffusion. Indeed, the Cox implementation of isopycnal diffusion in
+GFDL-type models requires a minimum background horizontal diffusion
+for numerical stability reasons.  To overcome this problem, several
+techniques have been proposed in which the numerical schemes of the
+ocean model are modified \citep{Weaver_Eby_JPO97,
+  Griffies_al_JPO98}. Griffies's scheme is now available in \NEMO if
+\np{traldf\_grif\_iso} is set true; see Appdx \ref{sec:triad}. Here,
+another strategy is presented \citep{Lazar_PhD97}: a local
+filtering of the iso-neutral slopes (made on 9 grid-points) prevents
+the development of grid point noise generated by the iso-neutral
+diffusion operator (Fig.~\ref{Fig_LDF_ZDF1}). This allows an
+iso-neutral diffusion scheme without additional background horizontal
+mixing. This technique can be viewed as a diffusion operator that acts
+along large-scale (2~$\Delta$x) \gmcomment{2deltax doesnt seem very
+  large scale} iso-neutral surfaces. The diapycnal diffusion required
+for numerical stability is thus minimized and its net effect on the
+flow is quite small when compared to the effect of an horizontal
+background mixing.
 
 Nevertheless, this iso-neutral operator does not ensure that variance cannot increase,