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% $Header: /u/gcmpack/manual/part3/case_studies/hs_atmosphere/hs_atmos.tex,v 1.7 2004/10/14 14:24:28 cnh Exp $ |
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% $Name: $ |
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\section[Held-Suarez Atmosphere MITgcm Example]{Held-Suarez forcing atmospheric simulation on a latitude-longitude grid 2.8$^\circ$ resolution and on |
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a cube-sphere grid with 32 square cube faces.} |
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\label{www:tutorials} |
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\label{sect:eg-hs} |
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\begin{rawhtml} |
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<!-- CMIREDIR:eg-hs: --> |
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\end{rawhtml} |
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\bodytext{bgcolor="#FFFFFFFF"} |
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%\begin{center} |
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%{\Large \bf Using MITgcm to Simulate Global Climatological Ocean Circulation |
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%At Four Degree Resolution with Asynchronous Time Stepping} |
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% |
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%\vspace*{4mm} |
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% |
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%\vspace*{3mm} |
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%{\large May 2001} |
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%\end{center} |
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This example illustrates the use of the MITgcm for large scale atmospheric |
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circulation simulation. Two simulations are described |
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\begin{itemize} |
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\item global atmospheric circulation on a latitude-longitude grid and |
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\item global atmospheric circulation on a cube-sphere grid |
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\end{itemize} |
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The examples show how to use the isomorphic 'p-coordinate' scheme in |
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MITgcm to enable atmospheric simulation. |
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\subsection{Overview} |
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\label{www:tutorials} |
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|
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This example demonstrates using the MITgcm to simulate |
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the planetary atmospheric circulation in two ways. |
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In both cases the simulation is configured with flat orography. |
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In the first case shown a $2.8^{\circ} \times 2.8^{\circ}$ spherical polar |
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horizontal grid is employed. In the second case a cube-sphere horizontal |
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grid is used that projects a cube with face size of $32 \times 32$ onto a |
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sphere. |
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Five pressure corrdinate levels are used in the vertical, ranging in thickness |
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from $100\,{\rm mb}$ at the bottom of the atmosphere to $300\,{\rm mb}$ in the middle atmosphere. |
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The total depth of the atmosphere is $1000{\rm mb}$. |
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At this resolution, the configuration can be integrated forward for many years on a |
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single processor desktop computer. |
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\\ |
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The model is forced by relaxation to a radiative equilibrium profile |
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from Held and Suarez \cite{held-suar:94}. Initial conditions are a |
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statically stable thermal gradient and no motion. The atmosphere |
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in these experiments is dry and the only active ``physics'' are the |
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terms in the Held and Suarez \cite{held-suar:94} formula. The |
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MITgcm intermediate atmospheric physics package (see \ref{sec:pkg:aim}) and |
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MITgcm high-end physics package ( see \ref{sec:pkg:fizhi}) are turned off. |
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Altogether, this yields the following forcing |
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(from Held and Suarez \cite{held-suar:94}) that is applied to the fluid: |
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\begin{eqnarray} |
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\label{EQ:eg-hs-global_forcing} |
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\label{EQ:eg-hs-global_forcing_fu} |
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\vec{{\cal F}_{u}} & = & -k_{v}(p)\vec{u} |
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\\ |
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\label{EQ:eg-hs-global_forcing_ft} |
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{\cal F}_{\theta} & = & -k_{T}(\phi,p)[\theta-\theta_{eq}(\phi,p)] |
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\\ |
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\end{eqnarray} |
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|
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\noindent where ${\vec{\cal F}_{u}}$, ${\cal F}_{\theta}$, |
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are the forcing terms in the zonal and meridional |
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momentum and in the potential temperature |
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equations respectively. |
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The term $k_{v}$ in equation (\ref{EQ:eg-hs-global_forcing_fu}) applies a |
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linear frictional drag (Rayleigh damping) that is active within the |
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planetary boundary layer. It is defined so as to decay with |
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height according to |
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\begin{eqnarray} |
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\label{EQ:eg-hs-define_kv} |
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k_{v} & = & k_{f}{\rm max}(0,(p_{\rm{k}}/p^{0}_{s}-\sigma_{b})/(1-\sigma_{b})) |
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\\ |
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\sigma_{b} & = & 0.7 |
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\\ |
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k_{f} & = & 1{\rm day}^{-1} |
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\end{eqnarray} |
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|
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where $p_{\rm{k}}$ is the pressure level of the cell center for level $\rm{k}$ |
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and $p^{0}_{s}$ is the pressure at the base of the atmospheric column. |
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|
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\subsection{Discrete Numerical Configuration} |
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\label{www:tutorials} |
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|
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The model is configured in hydrostatic form. The domain is discretised with |
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a uniform grid spacing in latitude and longitude on the sphere |
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$\Delta \phi=\Delta \lambda=4^{\circ}$, so |
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that there are ninety grid cells in the zonal and forty in the |
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meridional direction. The internal model coordinate variables |
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$x$ and $y$ are initialized according to |
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\begin{eqnarray} |
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x=r\cos(\phi),~\Delta x & = &r\cos(\Delta \phi) \\ |
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y=r\lambda,~\Delta x &= &r\Delta \lambda |
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\end{eqnarray} |
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Arctic polar regions are not |
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included in this experiment. Meridionally the model extends from |
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$80^{\circ}{\rm S}$ to $80^{\circ}{\rm N}$. |
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Vertically the model is configured with twenty layers with the |
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following thicknesses |
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$\Delta z_{1} = 50\,{\rm m},\, |
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\Delta z_{2} = 50\,{\rm m},\, |
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\Delta z_{3} = 55\,{\rm m},\, |
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\Delta z_{4} = 60\,{\rm m},\, |
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\Delta z_{5} = 65\,{\rm m},\, |
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$ |
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$ |
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\Delta z_{6}~=~70\,{\rm m},\, |
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\Delta z_{7}~=~80\,{\rm m},\, |
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\Delta z_{8}~=95\,{\rm m},\, |
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\Delta z_{9}=120\,{\rm m},\, |
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\Delta z_{10}=155\,{\rm m},\, |
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$ |
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$ |
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\Delta z_{11}=200\,{\rm m},\, |
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\Delta z_{12}=260\,{\rm m},\, |
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\Delta z_{13}=320\,{\rm m},\, |
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\Delta z_{14}=400\,{\rm m},\, |
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\Delta z_{15}=480\,{\rm m},\, |
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$ |
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$ |
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\Delta z_{16}=570\,{\rm m},\, |
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\Delta z_{17}=655\,{\rm m},\, |
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\Delta z_{18}=725\,{\rm m},\, |
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\Delta z_{19}=775\,{\rm m},\, |
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\Delta z_{20}=815\,{\rm m} |
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$ (here the numeric subscript indicates the model level index number, ${\tt k}$). |
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The implicit free surface form of the pressure equation described in Marshall et. al |
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\cite{marshall:97a} is employed. A Laplacian operator, $\nabla^2$, provides viscous |
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dissipation. Thermal and haline diffusion is also represented by a Laplacian operator. |
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Wind-stress forcing is added to the momentum equations for both |
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the zonal flow, $u$ and the meridional flow $v$, according to equations |
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(\ref{EQ:eg-hs-global_forcing_fu}) and (\ref{EQ:eg-hs-global_forcing_fv}). |
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Thermodynamic forcing inputs are added to the equations for |
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potential temperature, $\theta$, and salinity, $S$, according to equations |
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(\ref{EQ:eg-hs-global_forcing_ft}) and (\ref{EQ:eg-hs-global_forcing_fs}). |
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This produces a set of equations solved in this configuration as follows: |
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\begin{eqnarray} |
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\label{EQ:eg-hs-model_equations} |
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\frac{Du}{Dt} - fv + |
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\frac{1}{\rho}\frac{\partial p^{'}}{\partial x} - |
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\nabla_{h}\cdot A_{h}\nabla_{h}u - |
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\frac{\partial}{\partial z}A_{z}\frac{\partial u}{\partial z} |
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& = & |
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\begin{cases} |
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{\cal F}_u & \text{(surface)} \\ |
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0 & \text{(interior)} |
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\end{cases} |
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\\ |
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\frac{Dv}{Dt} + fu + |
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\frac{1}{\rho}\frac{\partial p^{'}}{\partial y} - |
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\nabla_{h}\cdot A_{h}\nabla_{h}v - |
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\frac{\partial}{\partial z}A_{z}\frac{\partial v}{\partial z} |
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& = & |
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\begin{cases} |
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{\cal F}_v & \text{(surface)} \\ |
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0 & \text{(interior)} |
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\end{cases} |
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\\ |
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\frac{\partial \eta}{\partial t} + \nabla_{h}\cdot \vec{u} |
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&=& |
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0 |
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\\ |
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\frac{D\theta}{Dt} - |
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\nabla_{h}\cdot K_{h}\nabla_{h}\theta |
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- \frac{\partial}{\partial z}\Gamma(K_{z})\frac{\partial\theta}{\partial z} |
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& = & |
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\begin{cases} |
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{\cal F}_\theta & \text{(surface)} \\ |
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0 & \text{(interior)} |
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\end{cases} |
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\\ |
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\frac{D s}{Dt} - |
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\nabla_{h}\cdot K_{h}\nabla_{h}s |
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- \frac{\partial}{\partial z}\Gamma(K_{z})\frac{\partial s}{\partial z} |
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& = & |
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\begin{cases} |
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{\cal F}_s & \text{(surface)} \\ |
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0 & \text{(interior)} |
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\end{cases} |
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\\ |
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g\rho_{0} \eta + \int^{0}_{-z}\rho^{'} dz & = & p^{'} |
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\end{eqnarray} |
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\noindent where $u=\frac{Dx}{Dt}=r \cos(\phi)\frac{D \lambda}{Dt}$ and |
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$v=\frac{Dy}{Dt}=r \frac{D \phi}{Dt}$ |
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are the zonal and meridional components of the |
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flow vector, $\vec{u}$, on the sphere. As described in |
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MITgcm Numerical Solution Procedure \ref{chap:discretization}, the time |
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evolution of potential temperature, $\theta$, equation is solved prognostically. |
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The total pressure, $p$, is diagnosed by summing pressure due to surface |
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elevation $\eta$ and the hydrostatic pressure. |
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\\ |
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\subsubsection{Numerical Stability Criteria} |
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\label{www:tutorials} |
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The Laplacian dissipation coefficient, $A_{h}$, is set to $5 \times 10^5 m s^{-1}$. |
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This value is chosen to yield a Munk layer width \cite{adcroft:95}, |
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\begin{eqnarray} |
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\label{EQ:eg-hs-munk_layer} |
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M_{w} = \pi ( \frac { A_{h} }{ \beta } )^{\frac{1}{3}} |
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\end{eqnarray} |
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\noindent of $\approx 600$km. This is greater than the model |
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resolution in low-latitudes, $\Delta x \approx 400{\rm km}$, ensuring that the frictional |
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boundary layer is adequately resolved. |
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\\ |
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\noindent The model is stepped forward with a |
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time step $\delta t_{\theta}=30~{\rm hours}$ for thermodynamic variables and |
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$\delta t_{v}=40~{\rm minutes}$ for momentum terms. With this time step, the stability |
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parameter to the horizontal Laplacian friction \cite{adcroft:95} |
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\begin{eqnarray} |
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\label{EQ:eg-hs-laplacian_stability} |
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S_{l} = 4 \frac{A_{h} \delta t_{v}}{{\Delta x}^2} |
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\end{eqnarray} |
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\noindent evaluates to 0.16 at a latitude of $\phi=80^{\circ}$, which is below the |
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0.3 upper limit for stability. The zonal grid spacing $\Delta x$ is smallest at |
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$\phi=80^{\circ}$ where $\Delta x=r\cos(\phi)\Delta \phi\approx 77{\rm km}$. |
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\\ |
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\noindent The vertical dissipation coefficient, $A_{z}$, is set to |
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$1\times10^{-3} {\rm m}^2{\rm s}^{-1}$. The associated stability limit |
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\begin{eqnarray} |
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\label{EQ:eg-hs-laplacian_stability_z} |
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S_{l} = 4 \frac{A_{z} \delta t_{v}}{{\Delta z}^2} |
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\end{eqnarray} |
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\noindent evaluates to $0.015$ for the smallest model |
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level spacing ($\Delta z_{1}=50{\rm m}$) which is again well below |
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the upper stability limit. |
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\\ |
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The values of the horizontal ($K_{h}$) and vertical ($K_{z}$) diffusion coefficients |
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for both temperature and salinity are set to $1 \times 10^{3}~{\rm m}^{2}{\rm s}^{-1}$ |
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and $3 \times 10^{-5}~{\rm m}^{2}{\rm s}^{-1}$ respectively. The stability limit |
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related to $K_{h}$ will be at $\phi=80^{\circ}$ where $\Delta x \approx 77 {\rm km}$. |
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Here the stability parameter |
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\begin{eqnarray} |
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\label{EQ:eg-hs-laplacian_stability_xtheta} |
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S_{l} = \frac{4 K_{h} \delta t_{\theta}}{{\Delta x}^2} |
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\end{eqnarray} |
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evaluates to $0.07$, well below the stability limit of $S_{l} \approx 0.5$. The |
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stability parameter related to $K_{z}$ |
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\begin{eqnarray} |
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\label{EQ:eg-hs-laplacian_stability_ztheta} |
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S_{l} = \frac{4 K_{z} \delta t_{\theta}}{{\Delta z}^2} |
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\end{eqnarray} |
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evaluates to $0.005$ for $\min(\Delta z)=50{\rm m}$, well below the stability limit |
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of $S_{l} \approx 0.5$. |
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\\ |
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\noindent The numerical stability for inertial oscillations |
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\cite{adcroft:95} |
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\begin{eqnarray} |
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\label{EQ:eg-hs-inertial_stability} |
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S_{i} = f^{2} {\delta t_v}^2 |
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\end{eqnarray} |
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\noindent evaluates to $0.24$ for $f=2\omega\sin(80^{\circ})=1.43\times10^{-4}~{\rm s}^{-1}$, which is close to |
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the $S_{i} < 1$ upper limit for stability. |
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\\ |
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\noindent The advective CFL \cite{adcroft:95} for a extreme maximum |
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horizontal flow |
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speed of $ | \vec{u} | = 2 ms^{-1}$ |
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\begin{eqnarray} |
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\label{EQ:eg-hs-cfl_stability} |
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S_{a} = \frac{| \vec{u} | \delta t_{v}}{ \Delta x} |
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\end{eqnarray} |
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\noindent evaluates to $6 \times 10^{-2}$. This is well below the stability |
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limit of 0.5. |
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\\ |
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\noindent The stability parameter for internal gravity waves propagating |
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with a maximum speed of $c_{g}=10~{\rm ms}^{-1}$ |
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\cite{adcroft:95} |
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\begin{eqnarray} |
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\label{EQ:eg-hs-gfl_stability} |
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S_{c} = \frac{c_{g} \delta t_{v}}{ \Delta x} |
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\end{eqnarray} |
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\noindent evaluates to $3 \times 10^{-1}$. This is close to the linear |
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stability limit of 0.5. |
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\subsection{Experiment Configuration} |
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\label{www:tutorials} |
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\label{SEC:eg-hs_examp_exp_config} |
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The model configuration for this experiment resides under the |
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directory {\it verification/hs94.128x64x5}. The experiment files |
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\begin{itemize} |
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\item {\it input/data} |
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\item {\it input/data.pkg} |
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\item {\it input/eedata}, |
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\item {\it input/windx.bin}, |
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\item {\it input/windy.bin}, |
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\item {\it input/salt.bin}, |
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\item {\it input/theta.bin}, |
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\item {\it input/SSS.bin}, |
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\item {\it input/SST.bin}, |
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\item {\it input/topog.bin}, |
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\item {\it code/CPP\_EEOPTIONS.h} |
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\item {\it code/CPP\_OPTIONS.h}, |
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\item {\it code/SIZE.h}. |
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\end{itemize} |
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contain the code customizations and parameter settings for these |
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experiments. Below we describe the customizations |
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to these files associated with this experiment. |
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\subsubsection{File {\it input/data}} |
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\label{www:tutorials} |
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|
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This file, reproduced completely below, specifies the main parameters |
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for the experiment. The parameters that are significant for this configuration |
336 |
|
|
are |
337 |
|
|
|
338 |
|
|
\begin{itemize} |
339 |
|
|
|
340 |
|
|
\item Lines 7-10 and 11-14 |
341 |
|
|
\begin{verbatim} tRef= 16.0 , 15.2 , 14.5 , 13.9 , 13.3 , \end{verbatim} |
342 |
|
|
$\cdots$ \\ |
343 |
|
|
set reference values for potential |
344 |
|
|
temperature and salinity at each model level in units of $^{\circ}$C and |
345 |
|
|
${\rm ppt}$. The entries are ordered from surface to depth. |
346 |
|
|
Density is calculated from anomalies at each level evaluated |
347 |
|
|
with respect to the reference values set here.\\ |
348 |
|
|
\fbox{ |
349 |
|
|
\begin{minipage}{5.0in} |
350 |
|
|
{\it S/R INI\_THETA}({\it ini\_theta.F}) |
351 |
|
|
\end{minipage} |
352 |
|
|
} |
353 |
|
|
|
354 |
|
|
|
355 |
|
|
\item Line 15, |
356 |
|
|
\begin{verbatim} viscAz=1.E-3, \end{verbatim} |
357 |
|
|
this line sets the vertical Laplacian dissipation coefficient to |
358 |
|
|
$1 \times 10^{-3} {\rm m^{2}s^{-1}}$. Boundary conditions |
359 |
|
|
for this operator are specified later. This variable is copied into |
360 |
|
|
model general vertical coordinate variable {\bf viscAr}. |
361 |
|
|
|
362 |
|
|
\fbox{ |
363 |
|
|
\begin{minipage}{5.0in} |
364 |
|
|
{\it S/R CALC\_DIFFUSIVITY}({\it calc\_diffusivity.F}) |
365 |
|
|
\end{minipage} |
366 |
|
|
} |
367 |
|
|
|
368 |
|
|
\item Line 16, |
369 |
|
|
\begin{verbatim} |
370 |
|
|
viscAh=5.E5, |
371 |
|
|
\end{verbatim} |
372 |
|
|
this line sets the horizontal Laplacian frictional dissipation coefficient to |
373 |
|
|
$5 \times 10^{5} {\rm m^{2}s^{-1}}$. Boundary conditions |
374 |
|
|
for this operator are specified later. |
375 |
|
|
|
376 |
|
|
\item Lines 17, |
377 |
|
|
\begin{verbatim} |
378 |
|
|
no_slip_sides=.FALSE. |
379 |
|
|
\end{verbatim} |
380 |
|
|
this line selects a free-slip lateral boundary condition for |
381 |
|
|
the horizontal Laplacian friction operator |
382 |
|
|
e.g. $\frac{\partial u}{\partial y}$=0 along boundaries in $y$ and |
383 |
|
|
$\frac{\partial v}{\partial x}$=0 along boundaries in $x$. |
384 |
|
|
|
385 |
|
|
\item Lines 9, |
386 |
|
|
\begin{verbatim} |
387 |
|
|
no_slip_bottom=.TRUE. |
388 |
|
|
\end{verbatim} |
389 |
|
|
this line selects a no-slip boundary condition for bottom |
390 |
|
|
boundary condition in the vertical Laplacian friction operator |
391 |
|
|
e.g. $u=v=0$ at $z=-H$, where $H$ is the local depth of the domain. |
392 |
|
|
|
393 |
|
|
\item Line 19, |
394 |
|
|
\begin{verbatim} |
395 |
|
|
diffKhT=1.E3, |
396 |
|
|
\end{verbatim} |
397 |
|
|
this line sets the horizontal diffusion coefficient for temperature |
398 |
|
|
to $1000\,{\rm m^{2}s^{-1}}$. The boundary condition on this |
399 |
|
|
operator is $\frac{\partial}{\partial x}=\frac{\partial}{\partial y}=0$ on |
400 |
|
|
all boundaries. |
401 |
|
|
|
402 |
|
|
\item Line 20, |
403 |
|
|
\begin{verbatim} |
404 |
|
|
diffKzT=3.E-5, |
405 |
|
|
\end{verbatim} |
406 |
|
|
this line sets the vertical diffusion coefficient for temperature |
407 |
|
|
to $3 \times 10^{-5}\,{\rm m^{2}s^{-1}}$. The boundary |
408 |
|
|
condition on this operator is $\frac{\partial}{\partial z}=0$ at both |
409 |
|
|
the upper and lower boundaries. |
410 |
|
|
|
411 |
|
|
\item Line 21, |
412 |
|
|
\begin{verbatim} |
413 |
|
|
diffKhS=1.E3, |
414 |
|
|
\end{verbatim} |
415 |
|
|
this line sets the horizontal diffusion coefficient for salinity |
416 |
|
|
to $1000\,{\rm m^{2}s^{-1}}$. The boundary condition on this |
417 |
|
|
operator is $\frac{\partial}{\partial x}=\frac{\partial}{\partial y}=0$ on |
418 |
|
|
all boundaries. |
419 |
|
|
|
420 |
|
|
\item Line 22, |
421 |
|
|
\begin{verbatim} |
422 |
|
|
diffKzS=3.E-5, |
423 |
|
|
\end{verbatim} |
424 |
|
|
this line sets the vertical diffusion coefficient for salinity |
425 |
|
|
to $3 \times 10^{-5}\,{\rm m^{2}s^{-1}}$. The boundary |
426 |
|
|
condition on this operator is $\frac{\partial}{\partial z}=0$ at both |
427 |
|
|
the upper and lower boundaries. |
428 |
|
|
|
429 |
|
|
\item Lines 23-26 |
430 |
|
|
\begin{verbatim} |
431 |
|
|
beta=1.E-11, |
432 |
|
|
\end{verbatim} |
433 |
|
|
\vspace{-5mm}$\cdots$\\ |
434 |
|
|
These settings do not apply for this experiment. |
435 |
|
|
|
436 |
|
|
\item Line 27, |
437 |
|
|
\begin{verbatim} |
438 |
|
|
gravity=9.81, |
439 |
|
|
\end{verbatim} |
440 |
|
|
Sets the gravitational acceleration coefficient to $9.81{\rm m}{\rm s}^{-1}$.\\ |
441 |
|
|
\fbox{ |
442 |
|
|
\begin{minipage}{5.0in} |
443 |
|
|
{\it S/R CALC\_PHI\_HYD}~({\it calc\_phi\_hyd.F})\\ |
444 |
|
|
{\it S/R INI\_CG2D}~({\it ini\_cg2d.F})\\ |
445 |
|
|
{\it S/R INI\_CG3D}~({\it ini\_cg3d.F})\\ |
446 |
|
|
{\it S/R INI\_PARMS}~({\it ini\_parms.F})\\ |
447 |
|
|
{\it S/R SOLVE\_FOR\_PRESSURE}~({\it solve\_for\_pressure.F}) |
448 |
|
|
\end{minipage} |
449 |
|
|
} |
450 |
|
|
|
451 |
|
|
|
452 |
|
|
\item Line 28-29, |
453 |
|
|
\begin{verbatim} |
454 |
|
|
rigidLid=.FALSE., |
455 |
|
|
implicitFreeSurface=.TRUE., |
456 |
|
|
\end{verbatim} |
457 |
|
|
Selects the barotropic pressure equation to be the implicit free surface |
458 |
|
|
formulation. |
459 |
|
|
|
460 |
|
|
\item Line 30, |
461 |
|
|
\begin{verbatim} |
462 |
|
|
eosType='POLY3', |
463 |
|
|
\end{verbatim} |
464 |
|
|
Selects the third order polynomial form of the equation of state.\\ |
465 |
|
|
\fbox{ |
466 |
|
|
\begin{minipage}{5.0in} |
467 |
|
|
{\it S/R FIND\_RHO}~({\it find\_rho.F})\\ |
468 |
|
|
{\it S/R FIND\_ALPHA}~({\it find\_alpha.F}) |
469 |
|
|
\end{minipage} |
470 |
|
|
} |
471 |
|
|
|
472 |
|
|
\item Line 31, |
473 |
|
|
\begin{verbatim} |
474 |
|
|
readBinaryPrec=32, |
475 |
|
|
\end{verbatim} |
476 |
|
|
Sets format for reading binary input datasets holding model fields to |
477 |
|
|
use 32-bit representation for floating-point numbers.\\ |
478 |
|
|
\fbox{ |
479 |
|
|
\begin{minipage}{5.0in} |
480 |
|
|
{\it S/R READ\_WRITE\_FLD}~({\it read\_write\_fld.F})\\ |
481 |
|
|
{\it S/R READ\_WRITE\_REC}~({\it read\_write\_rec.F}) |
482 |
|
|
\end{minipage} |
483 |
|
|
} |
484 |
|
|
|
485 |
|
|
\item Line 36, |
486 |
|
|
\begin{verbatim} |
487 |
|
|
cg2dMaxIters=1000, |
488 |
|
|
\end{verbatim} |
489 |
|
|
Sets maximum number of iterations the two-dimensional, conjugate |
490 |
|
|
gradient solver will use, {\bf irrespective of convergence |
491 |
|
|
criteria being met}.\\ |
492 |
|
|
\fbox{ |
493 |
|
|
\begin{minipage}{5.0in} |
494 |
|
|
{\it S/R CG2D}~({\it cg2d.F}) |
495 |
|
|
\end{minipage} |
496 |
|
|
} |
497 |
|
|
|
498 |
|
|
\item Line 37, |
499 |
|
|
\begin{verbatim} |
500 |
|
|
cg2dTargetResidual=1.E-13, |
501 |
|
|
\end{verbatim} |
502 |
|
|
Sets the tolerance which the two-dimensional, conjugate |
503 |
|
|
gradient solver will use to test for convergence in equation |
504 |
|
|
\ref{EQ:eg-hs-congrad_2d_resid} to $1 \times 10^{-13}$. |
505 |
|
|
Solver will iterate until |
506 |
|
|
tolerance falls below this value or until the maximum number of |
507 |
|
|
solver iterations is reached.\\ |
508 |
|
|
\fbox{ |
509 |
|
|
\begin{minipage}{5.0in} |
510 |
|
|
{\it S/R CG2D}~({\it cg2d.F}) |
511 |
|
|
\end{minipage} |
512 |
|
|
} |
513 |
|
|
|
514 |
|
|
\item Line 42, |
515 |
|
|
\begin{verbatim} |
516 |
|
|
startTime=0, |
517 |
|
|
\end{verbatim} |
518 |
|
|
Sets the starting time for the model internal time counter. |
519 |
|
|
When set to non-zero this option implicitly requests a |
520 |
|
|
checkpoint file be read for initial state. |
521 |
|
|
By default the checkpoint file is named according to |
522 |
|
|
the integer number of time steps in the {\bf startTime} value. |
523 |
|
|
The internal time counter works in seconds. |
524 |
|
|
|
525 |
|
|
\item Line 43, |
526 |
|
|
\begin{verbatim} |
527 |
|
|
endTime=2808000., |
528 |
|
|
\end{verbatim} |
529 |
|
|
Sets the time (in seconds) at which this simulation will terminate. |
530 |
|
|
At the end of a simulation a checkpoint file is automatically |
531 |
|
|
written so that a numerical experiment can consist of multiple |
532 |
|
|
stages. |
533 |
|
|
|
534 |
|
|
\item Line 44, |
535 |
|
|
\begin{verbatim} |
536 |
|
|
#endTime=62208000000, |
537 |
|
|
\end{verbatim} |
538 |
|
|
A commented out setting for endTime for a 2000 year simulation. |
539 |
|
|
|
540 |
|
|
\item Line 45, |
541 |
|
|
\begin{verbatim} |
542 |
|
|
deltaTmom=2400.0, |
543 |
|
|
\end{verbatim} |
544 |
|
|
Sets the timestep $\delta t_{v}$ used in the momentum equations to |
545 |
|
|
$20~{\rm mins}$. |
546 |
|
|
See section \ref{SEC:mom_time_stepping}. |
547 |
|
|
|
548 |
|
|
\fbox{ |
549 |
|
|
\begin{minipage}{5.0in} |
550 |
|
|
{\it S/R TIMESTEP}({\it timestep.F}) |
551 |
|
|
\end{minipage} |
552 |
|
|
} |
553 |
|
|
|
554 |
|
|
\item Line 46, |
555 |
|
|
\begin{verbatim} |
556 |
|
|
tauCD=321428., |
557 |
|
|
\end{verbatim} |
558 |
|
|
Sets the D-grid to C-grid coupling time scale $\tau_{CD}$ used in the momentum equations. |
559 |
|
|
See section \ref{SEC:cd_scheme}. |
560 |
|
|
|
561 |
|
|
\fbox{ |
562 |
|
|
\begin{minipage}{5.0in} |
563 |
|
|
{\it S/R INI\_PARMS}({\it ini\_parms.F})\\ |
564 |
|
|
{\it S/R CALC\_MOM\_RHS}({\it calc\_mom\_rhs.F}) |
565 |
|
|
\end{minipage} |
566 |
|
|
} |
567 |
|
|
|
568 |
|
|
\item Line 47, |
569 |
|
|
\begin{verbatim} |
570 |
|
|
deltaTtracer=108000., |
571 |
|
|
\end{verbatim} |
572 |
|
|
Sets the default timestep, $\delta t_{\theta}$, for tracer equations to |
573 |
|
|
$30~{\rm hours}$. |
574 |
|
|
See section \ref{SEC:tracer_time_stepping}. |
575 |
|
|
|
576 |
|
|
\fbox{ |
577 |
|
|
\begin{minipage}{5.0in} |
578 |
|
|
{\it S/R TIMESTEP\_TRACER}({\it timestep\_tracer.F}) |
579 |
|
|
\end{minipage} |
580 |
|
|
} |
581 |
|
|
|
582 |
|
|
\item Line 47, |
583 |
|
|
\begin{verbatim} |
584 |
|
|
bathyFile='topog.box' |
585 |
|
|
\end{verbatim} |
586 |
|
|
This line specifies the name of the file from which the domain |
587 |
|
|
bathymetry is read. This file is a two-dimensional ($x,y$) map of |
588 |
|
|
depths. This file is assumed to contain 64-bit binary numbers |
589 |
|
|
giving the depth of the model at each grid cell, ordered with the x |
590 |
|
|
coordinate varying fastest. The points are ordered from low coordinate |
591 |
|
|
to high coordinate for both axes. The units and orientation of the |
592 |
|
|
depths in this file are the same as used in the MITgcm code. In this |
593 |
|
|
experiment, a depth of $0m$ indicates a solid wall and a depth |
594 |
|
|
of $-2000m$ indicates open ocean. The matlab program |
595 |
|
|
{\it input/gendata.m} shows an example of how to generate a |
596 |
|
|
bathymetry file. |
597 |
|
|
|
598 |
|
|
|
599 |
|
|
\item Line 50, |
600 |
|
|
\begin{verbatim} |
601 |
|
|
zonalWindFile='windx.sin_y' |
602 |
|
|
\end{verbatim} |
603 |
|
|
This line specifies the name of the file from which the x-direction |
604 |
|
|
surface wind stress is read. This file is also a two-dimensional |
605 |
|
|
($x,y$) map and is enumerated and formatted in the same manner as the |
606 |
|
|
bathymetry file. The matlab program {\it input/gendata.m} includes example |
607 |
|
|
code to generate a valid |
608 |
|
|
{\bf zonalWindFile} |
609 |
|
|
file. |
610 |
|
|
|
611 |
|
|
\end{itemize} |
612 |
|
|
|
613 |
|
|
\noindent other lines in the file {\it input/data} are standard values |
614 |
|
|
that are described in the MITgcm Getting Started and MITgcm Parameters |
615 |
|
|
notes. |
616 |
|
|
|
617 |
|
|
\begin{small} |
618 |
|
|
\input{part3/case_studies/climatalogical_ogcm/input/data} |
619 |
|
|
\end{small} |
620 |
|
|
|
621 |
|
|
\subsubsection{File {\it input/data.pkg}} |
622 |
adcroft |
1.2 |
\label{www:tutorials} |
623 |
cnh |
1.1 |
|
624 |
|
|
This file uses standard default values and does not contain |
625 |
|
|
customisations for this experiment. |
626 |
|
|
|
627 |
|
|
\subsubsection{File {\it input/eedata}} |
628 |
adcroft |
1.2 |
\label{www:tutorials} |
629 |
cnh |
1.1 |
|
630 |
|
|
This file uses standard default values and does not contain |
631 |
|
|
customisations for this experiment. |
632 |
|
|
|
633 |
|
|
\subsubsection{File {\it input/windx.sin\_y}} |
634 |
adcroft |
1.2 |
\label{www:tutorials} |
635 |
cnh |
1.1 |
|
636 |
|
|
The {\it input/windx.sin\_y} file specifies a two-dimensional ($x,y$) |
637 |
|
|
map of wind stress ,$\tau_{x}$, values. The units used are $Nm^{-2}$. |
638 |
|
|
Although $\tau_{x}$ is only a function of $y$n in this experiment |
639 |
|
|
this file must still define a complete two-dimensional map in order |
640 |
|
|
to be compatible with the standard code for loading forcing fields |
641 |
|
|
in MITgcm. The included matlab program {\it input/gendata.m} gives a complete |
642 |
|
|
code for creating the {\it input/windx.sin\_y} file. |
643 |
|
|
|
644 |
|
|
\subsubsection{File {\it input/topog.box}} |
645 |
adcroft |
1.2 |
\label{www:tutorials} |
646 |
cnh |
1.1 |
|
647 |
|
|
|
648 |
|
|
The {\it input/topog.box} file specifies a two-dimensional ($x,y$) |
649 |
|
|
map of depth values. For this experiment values are either |
650 |
|
|
$0m$ or $-2000\,{\rm m}$, corresponding respectively to a wall or to deep |
651 |
|
|
ocean. The file contains a raw binary stream of data that is enumerated |
652 |
|
|
in the same way as standard MITgcm two-dimensional, horizontal arrays. |
653 |
|
|
The included matlab program {\it input/gendata.m} gives a complete |
654 |
|
|
code for creating the {\it input/topog.box} file. |
655 |
|
|
|
656 |
|
|
\subsubsection{File {\it code/SIZE.h}} |
657 |
adcroft |
1.2 |
\label{www:tutorials} |
658 |
cnh |
1.1 |
|
659 |
|
|
Two lines are customized in this file for the current experiment |
660 |
|
|
|
661 |
|
|
\begin{itemize} |
662 |
|
|
|
663 |
|
|
\item Line 39, |
664 |
|
|
\begin{verbatim} sNx=60, \end{verbatim} this line sets |
665 |
|
|
the lateral domain extent in grid points for the |
666 |
|
|
axis aligned with the x-coordinate. |
667 |
|
|
|
668 |
|
|
\item Line 40, |
669 |
|
|
\begin{verbatim} sNy=60, \end{verbatim} this line sets |
670 |
|
|
the lateral domain extent in grid points for the |
671 |
|
|
axis aligned with the y-coordinate. |
672 |
|
|
|
673 |
|
|
\item Line 49, |
674 |
|
|
\begin{verbatim} Nr=4, \end{verbatim} this line sets |
675 |
|
|
the vertical domain extent in grid points. |
676 |
|
|
|
677 |
|
|
\end{itemize} |
678 |
|
|
|
679 |
|
|
\begin{small} |
680 |
|
|
\input{part3/case_studies/climatalogical_ogcm/code/SIZE.h} |
681 |
|
|
\end{small} |
682 |
|
|
|
683 |
|
|
\subsubsection{File {\it code/CPP\_OPTIONS.h}} |
684 |
adcroft |
1.2 |
\label{www:tutorials} |
685 |
cnh |
1.1 |
|
686 |
|
|
This file uses standard default values and does not contain |
687 |
|
|
customisations for this experiment. |
688 |
|
|
|
689 |
|
|
|
690 |
|
|
\subsubsection{File {\it code/CPP\_EEOPTIONS.h}} |
691 |
adcroft |
1.2 |
\label{www:tutorials} |
692 |
cnh |
1.1 |
|
693 |
|
|
This file uses standard default values and does not contain |
694 |
|
|
customisations for this experiment. |
695 |
|
|
|
696 |
|
|
\subsubsection{Other Files } |
697 |
adcroft |
1.2 |
\label{www:tutorials} |
698 |
cnh |
1.1 |
|
699 |
|
|
Other files relevant to this experiment are |
700 |
|
|
\begin{itemize} |
701 |
|
|
\item {\it model/src/ini\_cori.F}. This file initializes the model |
702 |
|
|
coriolis variables {\bf fCorU}. |
703 |
|
|
\item {\it model/src/ini\_spherical\_polar\_grid.F} |
704 |
|
|
\item {\it model/src/ini\_parms.F}, |
705 |
|
|
\item {\it input/windx.sin\_y}, |
706 |
|
|
\end{itemize} |
707 |
|
|
contain the code customisations and parameter settings for this |
708 |
|
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experiments. Below we describe the customisations |
709 |
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to these files associated with this experiment. |