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\section{Example: Surface driven convection} |
\section{Surface Driven Convection} |
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\label{sect:eg-bconv} |
\label{sect:eg-bconv} |
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\bodytext{bgcolor="#FFFFFFFF"} |
\bodytext{bgcolor="#FFFFFFFF"} |
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for the surface driven convection experiment. The domain is doubly periodic |
for the surface driven convection experiment. The domain is doubly periodic |
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with an initially uniform temperature of 20 $^oC$. |
with an initially uniform temperature of 20 $^oC$. |
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} |
} |
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\label{FIG:simulation_config} |
\label{FIG:eg-bconv-simulation_config} |
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\end{figure} |
\end{figure} |
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This experiment, figure \ref{FIG:simulation_config}, showcasing MITgcm's non-hydrostatic capability, was designed to explore |
This experiment, figure \ref{FIG:eg-bconv-simulation_config}, showcasing MITgcm's non-hydrostatic capability, was designed to explore |
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the temporal and spatial characteristics of convection plumes as they might exist during a |
the temporal and spatial characteristics of convection plumes as they might exist during a |
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period of oceanic deep convection. It is |
period of oceanic deep convection. It is |
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used in this experiment is linear |
used in this experiment is linear |
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\begin{equation} |
\begin{equation} |
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\label{EQ:linear1_eos} |
\label{EQ:eg-bconv-linear1_eos} |
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\rho = \rho_{0} ( 1 - \alpha_{\theta}\theta^{'} ) |
\rho = \rho_{0} ( 1 - \alpha_{\theta}\theta^{'} ) |
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\end{equation} |
\end{equation} |
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\noindent which is implemented in the model as a density anomaly equation |
\noindent which is implemented in the model as a density anomaly equation |
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\begin{equation} |
\begin{equation} |
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\label{EQ:linear1_eos_pert} |
\label{EQ:eg-bconv-linear1_eos_pert} |
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\rho^{'} = -\rho_{0}\alpha_{\theta}\theta^{'} |
\rho^{'} = -\rho_{0}\alpha_{\theta}\theta^{'} |
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\end{equation} |
\end{equation} |
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As the fluid in the surface layer is cooled (at a mean rate of 800 Wm$^2$), it becomes |
As the fluid in the surface layer is cooled (at a mean rate of 800 Wm$^2$), it becomes |
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convectively unstable and |
convectively unstable and |
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overturns, at first close to the grid-scale, but, as the flow matures, on larger scales |
overturns, at first close to the grid-scale, but, as the flow matures, on larger scales |
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(figures \ref{FIG:vertsection} and \ref{FIG:horizsection}), under the influence of |
(figures \ref{FIG:eg-bconv-vertsection} and \ref{FIG:eg-bconv-horizsection}), under the influence of |
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rotation ($f_o = 10^{-4}$ s$^{-1}$) . |
rotation ($f_o = 10^{-4}$ s$^{-1}$) . |
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\begin{rawhtml}MITGCM_INSERT_FIGURE_BEGIN surf-convection-vertsection\end{rawhtml} |
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\begin{figure} |
\begin{figure} |
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\begin{center} |
\begin{center} |
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\resizebox{15cm}{10cm}{ |
\resizebox{15cm}{10cm}{ |
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\end{center} |
\end{center} |
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\caption{ |
\caption{ |
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} |
} |
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\label{FIG:vertsection} |
\label{FIG:eg-bconv-vertsection} |
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\label{fig:surf-convection-vertsection} |
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\end{figure} |
\end{figure} |
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\begin{rawhtml}MITGCM_INSERT_FIGURE_END\end{rawhtml} |
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\begin{rawhtml}MITGCM_INSERT_FIGURE_BEGIN surf-convection-horizsection\end{rawhtml} |
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\begin{figure} |
\begin{figure} |
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\begin{center} |
\begin{center} |
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\resizebox{10cm}{10cm}{ |
\resizebox{10cm}{10cm}{ |
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\end{center} |
\end{center} |
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\caption{ |
\caption{ |
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} |
} |
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\label{FIG:horizsection} |
\label{FIG:eg-bconv-horizsection} |
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\label{fig:surf-convection-horizsection} |
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\end{figure} |
\end{figure} |
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\begin{rawhtml}MITGCM_INSERT_FIGURE_END\end{rawhtml} |
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Model parameters are specified in file {\it input/data}. The grid dimensions are |
Model parameters are specified in file {\it input/data}. The grid dimensions are |
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prescribed in {\it code/SIZE.h}. The forcing (file {\it input/Qsurf.bin}) is specified |
prescribed in {\it code/SIZE.h}. The forcing (file {\it input/Qsurf.bin}) is specified |
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pressure equation described in Marshall et. al \cite{marshall:97a} is |
pressure equation described in Marshall et. al \cite{marshall:97a} is |
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employed. A horizontal Laplacian operator $\nabla_{h}^2$ provides viscous |
employed. A horizontal Laplacian operator $\nabla_{h}^2$ provides viscous |
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dissipation. The thermodynamic forcing appears as a sink in the potential temperature, |
dissipation. The thermodynamic forcing appears as a sink in the potential temperature, |
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$\theta$, equation (\ref{EQ:global_forcing_ft}). This produces a set of equations |
$\theta$, equation (\ref{EQ:eg-bconv-global_forcing_ft}). This produces a set of equations |
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solved in this configuration as follows: |
solved in this configuration as follows: |
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\begin{eqnarray} |
\begin{eqnarray} |
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\label{EQ:model_equations} |
\label{EQ:eg-bconv-model_equations} |
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\frac{Du}{Dt} - fv + |
\frac{Du}{Dt} - fv + |
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\frac{1}{\rho}\frac{\partial p^{'}}{\partial x} - |
\frac{1}{\rho}\frac{\partial p^{'}}{\partial x} - |
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\nabla_{h}\cdot A_{h}\nabla_{h}u - |
\nabla_{h}\cdot A_{h}\nabla_{h}u - |
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50 m, the implied maximum timestep for stability, $\delta t_u$ is |
50 m, the implied maximum timestep for stability, $\delta t_u$ is |
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\begin{eqnarray} |
\begin{eqnarray} |
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\label{EQ:advectiveCFLcondition} |
\label{EQ:eg-bconv-advectiveCFLcondition} |
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%\delta t_u = \frac{\Delta x}{| \vec{u} \} = 50 s |
%\delta t_u = \frac{\Delta x}{| \vec{u} \} = 50 s |
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\end{eqnarray} |
\end{eqnarray} |
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\end{verbatim} |
\end{verbatim} |
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Sets the tolerance which the three-dimensional, conjugate |
Sets the tolerance which the three-dimensional, conjugate |
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gradient solver will use to test for convergence in equation |
gradient solver will use to test for convergence in equation |
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\ref{EQ:congrad_3d_resid} to $1 \times 10^{-9}$. |
\ref{EQ:eg-bconv-congrad_3d_resid} to $1 \times 10^{-9}$. |
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The solver will iterate until the |
The solver will iterate until the |
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tolerance falls below this value or until the maximum number of |
tolerance falls below this value or until the maximum number of |
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solver iterations is reached. Used in routine |
solver iterations is reached. Used in routine |
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\end{center} |
\end{center} |
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\caption{ |
\caption{ |
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} |
} |
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\label{FIG:Qsurf} |
\label{FIG:eg-bconv-Qsurf} |
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\end{figure} |
\end{figure} |
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\subsection{Running the example} |
\subsection{Running the example} |