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\section{Gent/McWiliams/Redi SGS Eddy parameterization} |
\subsection{GMREDI: Gent/McWiliams/Redi SGS Eddy Parameterization} |
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\label{sec:pkg:gmredi} |
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\begin{rawhtml} |
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There are two parts to the Redi/GM parameterization of geostrophic |
There are two parts to the Redi/GM parameterization of geostrophic |
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eddies. The first aims to mix tracer properties along isentropes |
eddies. The first aims to mix tracer properties along isentropes |
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that the horizontal fluxes are unmodified from the lateral diffusion |
that the horizontal fluxes are unmodified from the lateral diffusion |
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parameterization. |
parameterization. |
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\subsection{Redi scheme: Isopycnal diffusion} |
\subsubsection{Redi scheme: Isopycnal diffusion} |
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The Redi scheme diffuses tracers along isopycnals and introduces a |
The Redi scheme diffuses tracers along isopycnals and introduces a |
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term in the tendency (rhs) of such a tracer (here $\tau$) of the form: |
term in the tendency (rhs) of such a tracer (here $\tau$) of the form: |
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\end{equation} |
\end{equation} |
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\subsection{GM parameterization} |
\subsubsection{GM parameterization} |
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The GM parameterization aims to parameterise the ``advective'' or |
The GM parameterization aims to parameterise the ``advective'' or |
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``transport'' effect of geostrophic eddies by means of a ``bolus'' |
``transport'' effect of geostrophic eddies by means of a ``bolus'' |
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This is the form of the GM parameterization as applied by Donabasaglu, |
This is the form of the GM parameterization as applied by Donabasaglu, |
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1997, in MOM versions 1 and 2. |
1997, in MOM versions 1 and 2. |
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\subsection{Griffies Skew Flux} |
\subsubsection{Griffies Skew Flux} |
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Griffies notes that the discretisation of bolus velocities involves |
Griffies notes that the discretisation of bolus velocities involves |
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multiple layers of differencing and interpolation that potentially |
multiple layers of differencing and interpolation that potentially |
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\subsection{Variable $\kappa_{GM}$} |
\subsubsection{Variable $\kappa_{GM}$} |
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Visbeck et al., 1996, suggest making the eddy coefficient, |
Visbeck et al., 1996, suggest making the eddy coefficient, |
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$\kappa_{GM}$, a function of the Eady growth rate, |
$\kappa_{GM}$, a function of the Eady growth rate, |
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\end{displaymath} |
\end{displaymath} |
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\subsection{Tapering and stability} |
\subsubsection{Tapering and stability} |
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Experience with the GFDL model showed that the GM scheme has to be |
Experience with the GFDL model showed that the GM scheme has to be |
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matched to the convective parameterization. This was originally |
matched to the convective parameterization. This was originally |
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\begin{figure} |
\begin{figure} |
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\begin{center} |
\begin{center} |
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\resizebox{5.0in}{3.0in}{\includegraphics{part6/tapers.eps}} |
\resizebox{5.0in}{3.0in}{\includegraphics{s_phys_pkgs/figs/tapers.eps}} |
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\end{center} |
\end{center} |
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\caption{Taper functions used in GKW91 and DM95.} |
\caption{Taper functions used in GKW99 and DM95.} |
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\label{fig:tapers} |
\label{fig:tapers} |
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\end{figure} |
\end{figure} |
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\begin{figure} |
\begin{figure} |
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\begin{center} |
\begin{center} |
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\resizebox{5.0in}{3.0in}{\includegraphics{part6/effective_slopes.eps}} |
\resizebox{5.0in}{3.0in}{\includegraphics{s_phys_pkgs/figs/effective_slopes.eps}} |
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\end{center} |
\end{center} |
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\caption{Effective slope as a function of ``true'' slope using Cox |
\caption{Effective slope as a function of ``true'' slope using Cox |
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slope clipping, GKW91 limiting and DM95 limiting.} |
slope clipping, GKW91 limiting and DM95 limiting.} |
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\end{figure} |
\end{figure} |
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\subsubsection{Slope clipping} |
Slope clipping: |
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Deep convection sites and the mixed layer are indicated by |
Deep convection sites and the mixed layer are indicated by |
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homogenized, unstable or nearly unstable stratification. The slopes in |
homogenized, unstable or nearly unstable stratification. The slopes in |
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of the GM/Redi parameterization, re-introducing diabatic fluxes in |
of the GM/Redi parameterization, re-introducing diabatic fluxes in |
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regions where the limiting is in effect. |
regions where the limiting is in effect. |
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\subsubsection{Tapering: Gerdes, Koberle and Willebrand, Clim. Dyn. 1991} |
Tapering: Gerdes, Koberle and Willebrand, Clim. Dyn. 1991: |
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The tapering scheme used in Gerdes et al., 1991, (\cite{gkw91}) |
The tapering scheme used in Gerdes et al., 1999, (\cite{gkw:99}) |
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addressed two issues with the clipping method: the introduction of |
addressed two issues with the clipping method: the introduction of |
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large vertical fluxes in addition to convective adjustment fluxes is |
large vertical fluxes in addition to convective adjustment fluxes is |
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avoided by tapering the GM/Redi slopes back to zero in |
avoided by tapering the GM/Redi slopes back to zero in |
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The GKW tapering scheme is activated in the model by setting {\bf |
The GKW tapering scheme is activated in the model by setting {\bf |
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GM\_tap\-er\_scheme = 'gkw91'} in {\em data.gmredi}. |
GM\_tap\-er\_scheme = 'gkw91'} in {\em data.gmredi}. |
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\subsection{Tapering: Danabasoglu and McWilliams, J. Clim. 1995} |
\subsubsection{Tapering: Danabasoglu and McWilliams, J. Clim. 1995} |
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The tapering scheme used by Danabasoglu and McWilliams, 1995, |
The tapering scheme used by Danabasoglu and McWilliams, 1995, |
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\cite{DM95}, followed a similar procedure but used a different |
\cite{dm:95}, followed a similar procedure but used a different |
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tapering function, $f_1(S)$: |
tapering function, $f_1(S)$: |
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\begin{equation} |
\begin{equation} |
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f_1(S) = \frac{1}{2} \left( 1+\tanh \left[ \frac{S_c - |S|}{S_d} \right] \right) |
f_1(S) = \frac{1}{2} \left( 1+\tanh \left[ \frac{S_c - |S|}{S_d} \right] \right) |
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The DM tapering scheme is activated in the model by setting {\bf |
The DM tapering scheme is activated in the model by setting {\bf |
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GM\_tap\-er\_scheme = 'dm95'} in {\em data.gmredi}. |
GM\_tap\-er\_scheme = 'dm95'} in {\em data.gmredi}. |
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\subsection{Tapering: Large, Danabasoglu and Doney, JPO 1997} |
\subsubsection{Tapering: Large, Danabasoglu and Doney, JPO 1997} |
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The tapering used in Large et al., 1997, \cite{ldd97}, is based on the |
The tapering used in Large et al., 1997, \cite{ldd:97}, is based on the |
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DM95 tapering scheme, but also tapers the scheme with an additional |
DM95 tapering scheme, but also tapers the scheme with an additional |
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function of height, $f_2(z)$, so that the GM/Redi SGS fluxes are |
function of height, $f_2(z)$, so that the GM/Redi SGS fluxes are |
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reduced near the surface: |
reduced near the surface: |
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\label{fig-mixedlayer} |
\label{fig-mixedlayer} |
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\end{figure} |
\end{figure} |
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\subsubsection{Package Reference} |
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\label{sec:pkg:gmredi:diagnostics} |
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{\footnotesize |
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\begin{verbatim} |
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------------------------------------------------------------------------ |
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<-Name->|Levs|<-parsing code->|<-- Units -->|<- Tile (max=80c) |
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------------------------------------------------------------------------ |
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GM_VisbK| 1 |SM P M1 |m^2/s |Mixing coefficient from Visbeck etal parameterization |
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GM_Kux | 15 |UU P 177MR |m^2/s |K_11 element (U.point, X.dir) of GM-Redi tensor |
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GM_Kvy | 15 |VV P 176MR |m^2/s |K_22 element (V.point, Y.dir) of GM-Redi tensor |
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GM_Kuz | 15 |UU 179MR |m^2/s |K_13 element (U.point, Z.dir) of GM-Redi tensor |
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GM_Kvz | 15 |VV 178MR |m^2/s |K_23 element (V.point, Z.dir) of GM-Redi tensor |
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GM_Kwx | 15 |UM 181LR |m^2/s |K_31 element (W.point, X.dir) of GM-Redi tensor |
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GM_Kwy | 15 |VM 180LR |m^2/s |K_32 element (W.point, Y.dir) of GM-Redi tensor |
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GM_Kwz | 15 |WM P LR |m^2/s |K_33 element (W.point, Z.dir) of GM-Redi tensor |
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GM_PsiX | 15 |UU 184LR |m^2/s |GM Bolus transport stream-function : X component |
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GM_PsiY | 15 |VV 183LR |m^2/s |GM Bolus transport stream-function : Y component |
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GM_KuzTz| 15 |UU 186MR |degC.m^3/s |Redi Off-diagonal Tempetature flux: X component |
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GM_KvzTz| 15 |VV 185MR |degC.m^3/s |Redi Off-diagonal Tempetature flux: Y component |
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\end{verbatim} |
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} |
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\subsubsection{Experiments and tutorials that use gmredi} |
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\label{sec:pkg:gmredi:experiments} |
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\begin{itemize} |
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\item{Global Ocean tutorial, in tutorial\_global\_oce\_latlon verification directory, |
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described in section \ref{sec:eg-global} } |
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\item{ Front Relax experiment, in front\_relax verification directory.} |
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\item{ Ideal 2D Ocean experiment, in ideal\_2D\_oce verification directory.} |
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\end{itemize} |
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