88 |
\end{itemize} |
\end{itemize} |
89 |
|
|
90 |
Key publications reporting on and charting the development of the model are |
Key publications reporting on and charting the development of the model are |
91 |
\cite{hill:95,marshall:97a,marshall:97b,adcroft:97,marshall:98,adcroft:99,hill:99,maro-eta:99}: |
\cite{hill:95,marshall:97a,marshall:97b,adcroft:97,marshall:98,adcroft:99,hill:99,maro-eta:99,adcroft:04a,adcroft:04b,marshall:04}: |
92 |
|
|
93 |
\begin{verbatim} |
\begin{verbatim} |
94 |
Hill, C. and J. Marshall, (1995) |
Hill, C. and J. Marshall, (1995) |
142 |
|
|
143 |
\section{Illustrations of the model in action} |
\section{Illustrations of the model in action} |
144 |
|
|
145 |
The MITgcm has been designed and used to model a wide range of phenomena, |
MITgcm has been designed and used to model a wide range of phenomena, |
146 |
from convection on the scale of meters in the ocean to the global pattern of |
from convection on the scale of meters in the ocean to the global pattern of |
147 |
atmospheric winds - see figure \ref{fig:all-scales}. To give a flavor of the |
atmospheric winds - see figure \ref{fig:all-scales}. To give a flavor of the |
148 |
kinds of problems the model has been used to study, we briefly describe some |
kinds of problems the model has been used to study, we briefly describe some |
165 |
|
|
166 |
Figure \ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$ |
Figure \ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$ |
167 |
temperature field obtained using the atmospheric isomorph of MITgcm run at |
temperature field obtained using the atmospheric isomorph of MITgcm run at |
168 |
2.8$^{\circ }$ resolution on the cubed sphere. We see cold air over the pole |
$2.8^{\circ }$ resolution on the cubed sphere. We see cold air over the pole |
169 |
(blue) and warm air along an equatorial band (red). Fully developed |
(blue) and warm air along an equatorial band (red). Fully developed |
170 |
baroclinic eddies spawned in the northern hemisphere storm track are |
baroclinic eddies spawned in the northern hemisphere storm track are |
171 |
evident. There are no mountains or land-sea contrast in this calculation, |
evident. There are no mountains or land-sea contrast in this calculation, |
210 |
increased until the baroclinic instability process is resolved, numerical |
increased until the baroclinic instability process is resolved, numerical |
211 |
solutions of a different and much more realistic kind, can be obtained. |
solutions of a different and much more realistic kind, can be obtained. |
212 |
|
|
213 |
Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity |
Figure \ref{fig:ocean-gyres} shows the surface temperature and |
214 |
field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal |
velocity field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ |
215 |
resolution on a $lat-lon$ |
horizontal resolution on a \textit{lat-lon} grid in which the pole has |
216 |
grid in which the pole has been rotated by 90$^{\circ }$ on to the equator |
been rotated by $90^{\circ }$ on to the equator (to avoid the |
217 |
(to avoid the converging of meridian in northern latitudes). 21 vertical |
converging of meridian in northern latitudes). 21 vertical levels are |
218 |
levels are used in the vertical with a `lopped cell' representation of |
used in the vertical with a `lopped cell' representation of |
219 |
topography. The development and propagation of anomalously warm and cold |
topography. The development and propagation of anomalously warm and |
220 |
eddies can be clearly seen in the Gulf Stream region. The transport of |
cold eddies can be clearly seen in the Gulf Stream region. The |
221 |
warm water northward by the mean flow of the Gulf Stream is also clearly |
transport of warm water northward by the mean flow of the Gulf Stream |
222 |
visible. |
is also clearly visible. |
223 |
|
|
224 |
%% CNHbegin |
%% CNHbegin |
225 |
\input{part1/atl6_figure} |
\input{part1/atl6_figure} |
231 |
<!-- CMIREDIR:global_ocean_circulation: --> |
<!-- CMIREDIR:global_ocean_circulation: --> |
232 |
\end{rawhtml} |
\end{rawhtml} |
233 |
|
|
234 |
Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean currents at |
Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean |
235 |
the surface of a 4$^{\circ }$ |
currents at the surface of a $4^{\circ }$ global ocean model run with |
236 |
global ocean model run with 15 vertical levels. Lopped cells are used to |
15 vertical levels. Lopped cells are used to represent topography on a |
237 |
represent topography on a regular $lat-lon$ grid extending from 70$^{\circ |
regular \textit{lat-lon} grid extending from $70^{\circ }N$ to |
238 |
}N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with |
$70^{\circ }S$. The model is driven using monthly-mean winds with |
239 |
mixed boundary conditions on temperature and salinity at the surface. The |
mixed boundary conditions on temperature and salinity at the surface. |
240 |
transfer properties of ocean eddies, convection and mixing is parameterized |
The transfer properties of ocean eddies, convection and mixing is |
241 |
in this model. |
parameterized in this model. |
242 |
|
|
243 |
Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning |
Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning |
244 |
circulation of the global ocean in Sverdrups. |
circulation of the global ocean in Sverdrups. |
301 |
`automatic adjoint compiler'. These can be used in parameter sensitivity and |
`automatic adjoint compiler'. These can be used in parameter sensitivity and |
302 |
data assimilation studies. |
data assimilation studies. |
303 |
|
|
304 |
As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity} |
As one example of application of the MITgcm adjoint, Figure |
305 |
maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude |
\ref{fig:hf-sensitivity} maps the gradient $\frac{\partial J}{\partial |
306 |
of the overturning stream-function shown in figure \ref{fig:large-scale-circ} |
\mathcal{H}}$where $J$ is the magnitude of the overturning |
307 |
at 60$^{\circ }$N and $ |
stream-function shown in figure \ref{fig:large-scale-circ} at |
308 |
\mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over |
$60^{\circ }N$ and $ \mathcal{H}(\lambda,\varphi)$ is the mean, local |
309 |
a 100 year period. We see that $J$ is |
air-sea heat flux over a 100 year period. We see that $J$ is sensitive |
310 |
sensitive to heat fluxes over the Labrador Sea, one of the important sources |
to heat fluxes over the Labrador Sea, one of the important sources of |
311 |
of deep water for the thermohaline circulations. This calculation also |
deep water for the thermohaline circulations. This calculation also |
312 |
yields sensitivities to all other model parameters. |
yields sensitivities to all other model parameters. |
313 |
|
|
314 |
%%CNHbegin |
%%CNHbegin |
341 |
<!-- CMIREDIR:ocean_biogeo_cycles: --> |
<!-- CMIREDIR:ocean_biogeo_cycles: --> |
342 |
\end{rawhtml} |
\end{rawhtml} |
343 |
|
|
344 |
MITgcm is being used to study global biogeochemical cycles in the ocean. For |
MITgcm is being used to study global biogeochemical cycles in the |
345 |
example one can study the effects of interannual changes in meteorological |
ocean. For example one can study the effects of interannual changes in |
346 |
forcing and upper ocean circulation on the fluxes of carbon dioxide and |
meteorological forcing and upper ocean circulation on the fluxes of |
347 |
oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows |
carbon dioxide and oxygen between the ocean and atmosphere. Figure |
348 |
the annual air-sea flux of oxygen and its relation to density outcrops in |
\ref{fig:biogeo} shows the annual air-sea flux of oxygen and its |
349 |
the southern oceans from a single year of a global, interannually varying |
relation to density outcrops in the southern oceans from a single year |
350 |
simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution |
of a global, interannually varying simulation. The simulation is run |
351 |
telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown). |
at $1^{\circ}\times1^{\circ}$ resolution telescoping to |
352 |
|
$\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not |
353 |
|
shown). |
354 |
|
|
355 |
%%CNHbegin |
%%CNHbegin |
356 |
\input{part1/biogeo_figure} |
\input{part1/biogeo_figure} |
772 |
|
|
773 |
\subsubsection{Shallow atmosphere approximation} |
\subsubsection{Shallow atmosphere approximation} |
774 |
|
|
775 |
Most models are based on the `hydrostatic primitive equations' (HPE's) in |
Most models are based on the `hydrostatic primitive equations' (HPE's) |
776 |
which the vertical momentum equation is reduced to a statement of |
in which the vertical momentum equation is reduced to a statement of |
777 |
hydrostatic balance and the `traditional approximation' is made in which the |
hydrostatic balance and the `traditional approximation' is made in |
778 |
Coriolis force is treated approximately and the shallow atmosphere |
which the Coriolis force is treated approximately and the shallow |
779 |
approximation is made.\ The MITgcm need not make the `traditional |
atmosphere approximation is made. MITgcm need not make the |
780 |
approximation'. To be able to support consistent non-hydrostatic forms the |
`traditional approximation'. To be able to support consistent |
781 |
shallow atmosphere approximation can be relaxed - when dividing through by $ |
non-hydrostatic forms the shallow atmosphere approximation can be |
782 |
r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, |
relaxed - when dividing through by $ r $ in, for example, |
783 |
the radius of the earth. |
(\ref{eq:gu-speherical}), we do not replace $r$ by $a$, the radius of |
784 |
|
the earth. |
785 |
|
|
786 |
\subsubsection{Hydrostatic and quasi-hydrostatic forms} |
\subsubsection{Hydrostatic and quasi-hydrostatic forms} |
787 |
\label{sec:hydrostatic_and_quasi-hydrostatic_forms} |
\label{sec:hydrostatic_and_quasi-hydrostatic_forms} |
818 |
|
|
819 |
\subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} |
\subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} |
820 |
|
|
821 |
The MIT model presently supports a full non-hydrostatic ocean isomorph, but |
MITgcm presently supports a full non-hydrostatic ocean isomorph, but |
822 |
only a quasi-non-hydrostatic atmospheric isomorph. |
only a quasi-non-hydrostatic atmospheric isomorph. |
823 |
|
|
824 |
\paragraph{Non-hydrostatic Ocean} |
\paragraph{Non-hydrostatic Ocean} |
1077 |
|
|
1078 |
The mixing terms for the temperature and salinity equations have a similar |
The mixing terms for the temperature and salinity equations have a similar |
1079 |
form to that of momentum except that the diffusion tensor can be |
form to that of momentum except that the diffusion tensor can be |
1080 |
non-diagonal and have varying coefficients. $\qquad $ |
non-diagonal and have varying coefficients. |
1081 |
\begin{equation} |
\begin{equation} |
1082 |
D_{T,S}=\nabla .[\underline{\underline{K}}\nabla (T,S)]+K_{4}\nabla |
D_{T,S}=\nabla .[\underline{\underline{K}}\nabla (T,S)]+K_{4}\nabla |
1083 |
_{h}^{4}(T,S) \label{eq:diffusion} |
_{h}^{4}(T,S) \label{eq:diffusion} |
1216 |
surface ($\phi $ is imposed and $\omega \neq 0$). |
surface ($\phi $ is imposed and $\omega \neq 0$). |
1217 |
|
|
1218 |
\subsubsection{Splitting the geo-potential} |
\subsubsection{Splitting the geo-potential} |
1219 |
|
\label{sec:hpe-p-geo-potential-split} |
1220 |
|
|
1221 |
For the purposes of initialization and reducing round-off errors, the model |
For the purposes of initialization and reducing round-off errors, the model |
1222 |
deals with perturbations from reference (or ``standard'') profiles. For |
deals with perturbations from reference (or ``standard'') profiles. For |
1489 |
\end{equation*} |
\end{equation*} |
1490 |
|
|
1491 |
\begin{equation*} |
\begin{equation*} |
1492 |
v=r\frac{D\varphi }{Dt}\qquad |
v=r\frac{D\varphi }{Dt} |
1493 |
\end{equation*} |
\end{equation*} |
|
$\qquad \qquad \qquad \qquad $ |
|
1494 |
|
|
1495 |
\begin{equation*} |
\begin{equation*} |
1496 |
\dot{r}=\frac{Dr}{Dt} |
\dot{r}=\frac{Dr}{Dt} |
1500 |
distance of the particle from the center of the earth, $\Omega $ is the |
distance of the particle from the center of the earth, $\Omega $ is the |
1501 |
angular speed of rotation of the Earth and $D/Dt$ is the total derivative. |
angular speed of rotation of the Earth and $D/Dt$ is the total derivative. |
1502 |
|
|
1503 |
The `grad' ($\nabla $) and `div' ($\nabla $.) operators are defined by, in |
The `grad' ($\nabla $) and `div' ($\nabla\cdot$) operators are defined by, in |
1504 |
spherical coordinates: |
spherical coordinates: |
1505 |
|
|
1506 |
\begin{equation*} |
\begin{equation*} |
1510 |
\end{equation*} |
\end{equation*} |
1511 |
|
|
1512 |
\begin{equation*} |
\begin{equation*} |
1513 |
\nabla .v\equiv \frac{1}{r\cos \varphi }\left\{ \frac{\partial u}{\partial |
\nabla\cdot v\equiv \frac{1}{r\cos \varphi }\left\{ \frac{\partial u}{\partial |
1514 |
\lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} |
\lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} |
1515 |
+\frac{1}{r^{2}}\frac{\partial \left( r^{2}\dot{r}\right) }{\partial r} |
+\frac{1}{r^{2}}\frac{\partial \left( r^{2}\dot{r}\right) }{\partial r} |
1516 |
\end{equation*} |
\end{equation*} |