102 |
numerical algorithm and implementation that lie behind these calculations is |
numerical algorithm and implementation that lie behind these calculations is |
103 |
given later. Indeed many of the illustrative examples shown below can be |
given later. Indeed many of the illustrative examples shown below can be |
104 |
easily reproduced: simply download the model (the minimum you need is a PC |
easily reproduced: simply download the model (the minimum you need is a PC |
105 |
running linux, together with a FORTRAN\ 77 compiler) and follow the examples |
running Linux, together with a FORTRAN\ 77 compiler) and follow the examples |
106 |
described in detail in the documentation. |
described in detail in the documentation. |
107 |
|
|
108 |
\subsection{Global atmosphere: `Held-Suarez' benchmark} |
\subsection{Global atmosphere: `Held-Suarez' benchmark} |
126 |
%% CNHend |
%% CNHend |
127 |
|
|
128 |
As described in Adcroft (2001), a `cubed sphere' is used to discretize the |
As described in Adcroft (2001), a `cubed sphere' is used to discretize the |
129 |
globe permitting a uniform gridding and obviated the need to Fourier filter. |
globe permitting a uniform griding and obviated the need to Fourier filter. |
130 |
The `vector-invariant' form of MITgcm supports any orthogonal curvilinear |
The `vector-invariant' form of MITgcm supports any orthogonal curvilinear |
131 |
grid, of which the cubed sphere is just one of many choices. |
grid, of which the cubed sphere is just one of many choices. |
132 |
|
|
231 |
|
|
232 |
As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity} |
As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity} |
233 |
maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude |
maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude |
234 |
of the overturning streamfunction shown in figure \ref{fig:large-scale-circ} |
of the overturning stream-function shown in figure \ref{fig:large-scale-circ} |
235 |
at 60$^{\circ }$N and $ |
at 60$^{\circ }$N and $ |
236 |
\mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over |
\mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over |
237 |
a 100 year period. We see that $J$ is |
a 100 year period. We see that $J$ is |
248 |
An important application of MITgcm is in state estimation of the global |
An important application of MITgcm is in state estimation of the global |
249 |
ocean circulation. An appropriately defined `cost function', which measures |
ocean circulation. An appropriately defined `cost function', which measures |
250 |
the departure of the model from observations (both remotely sensed and |
the departure of the model from observations (both remotely sensed and |
251 |
insitu) over an interval of time, is minimized by adjusting `control |
in-situ) over an interval of time, is minimized by adjusting `control |
252 |
parameters' such as air-sea fluxes, the wind field, the initial conditions |
parameters' such as air-sea fluxes, the wind field, the initial conditions |
253 |
etc. Figure \ref{fig:assimilated-globes} shows an estimate of the time-mean |
etc. Figure \ref{fig:assimilated-globes} shows an estimate of the time-mean |
254 |
surface elevation of the ocean obtained by bringing the model in to |
surface elevation of the ocean obtained by bringing the model in to |
277 |
\subsection{Simulations of laboratory experiments} |
\subsection{Simulations of laboratory experiments} |
278 |
|
|
279 |
Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a |
Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a |
280 |
laboratory experiment enquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An |
laboratory experiment inquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An |
281 |
initially homogeneous tank of water ($1m$ in diameter) is driven from its |
initially homogeneous tank of water ($1m$ in diameter) is driven from its |
282 |
free surface by a rotating heated disk. The combined action of mechanical |
free surface by a rotating heated disk. The combined action of mechanical |
283 |
and thermal forcing creates a lens of fluid which becomes baroclinically |
and thermal forcing creates a lens of fluid which becomes baroclinically |
432 |
|
|
433 |
\begin{equation} |
\begin{equation} |
434 |
\dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \ |
\dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \ |
435 |
(oceansurface,bottomoftheatmosphere)} \label{eq:movingbc} |
(ocean surface,bottom of the atmosphere)} \label{eq:movingbc} |
436 |
\end{equation} |
\end{equation} |
437 |
|
|
438 |
Here |
Here |
1178 |
\label{eq:non-boussinesq} |
\label{eq:non-boussinesq} |
1179 |
\end{eqnarray} |
\end{eqnarray} |
1180 |
These equations permit acoustics modes, inertia-gravity waves, |
These equations permit acoustics modes, inertia-gravity waves, |
1181 |
non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline |
non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline |
1182 |
mode. As written, they cannot be integrated forward consistently - if we |
mode. As written, they cannot be integrated forward consistently - if we |
1183 |
step $\rho $ forward in (\ref{eq-zns-cont}), the answer will not be |
step $\rho $ forward in (\ref{eq-zns-cont}), the answer will not be |
1184 |
consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref |
consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref |