| 48 |
also presented. |
also presented. |
| 49 |
|
|
| 50 |
\section{Introduction} |
\section{Introduction} |
| 51 |
|
\begin{rawhtml} |
| 52 |
|
<!-- CMIREDIR:innovations: --> |
| 53 |
|
\end{rawhtml} |
| 54 |
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| 55 |
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| 56 |
MITgcm has a number of novel aspects: |
MITgcm has a number of novel aspects: |
| 57 |
|
|
| 61 |
models - see fig \ref{fig:onemodel} |
models - see fig \ref{fig:onemodel} |
| 62 |
|
|
| 63 |
%% CNHbegin |
%% CNHbegin |
| 64 |
\input{part1/one_model_figure} |
\input{s_overview/text/one_model_figure} |
| 65 |
%% CNHend |
%% CNHend |
| 66 |
|
|
| 67 |
\item it has a non-hydrostatic capability and so can be used to study both |
\item it has a non-hydrostatic capability and so can be used to study both |
| 68 |
small-scale and large scale processes - see fig \ref{fig:all-scales} |
small-scale and large scale processes - see fig \ref{fig:all-scales} |
| 69 |
|
|
| 70 |
%% CNHbegin |
%% CNHbegin |
| 71 |
\input{part1/all_scales_figure} |
\input{s_overview/text/all_scales_figure} |
| 72 |
%% CNHend |
%% CNHend |
| 73 |
|
|
| 74 |
\item finite volume techniques are employed yielding an intuitive |
\item finite volume techniques are employed yielding an intuitive |
| 76 |
orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes} |
orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes} |
| 77 |
|
|
| 78 |
%% CNHbegin |
%% CNHbegin |
| 79 |
\input{part1/fvol_figure} |
\input{s_overview/text/fvol_figure} |
| 80 |
%% CNHend |
%% CNHend |
| 81 |
|
|
| 82 |
\item tangent linear and adjoint counterparts are automatically maintained |
\item tangent linear and adjoint counterparts are automatically maintained |
| 87 |
computational platforms. |
computational platforms. |
| 88 |
\end{itemize} |
\end{itemize} |
| 89 |
|
|
| 90 |
|
|
| 91 |
Key publications reporting on and charting the development of the model are |
Key publications reporting on and charting the development of the model are |
| 92 |
\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,mars-eta:98,adcroft:99,hill:99,maro-eta:99,adcroft:04a,adcroft:04b,marshall:04} |
| 93 |
|
(an overview on the model formulation can also be found in \cite{adcroft:04c}): |
| 94 |
|
|
| 95 |
\begin{verbatim} |
\begin{verbatim} |
| 96 |
Hill, C. and J. Marshall, (1995) |
Hill, C. and J. Marshall, (1995) |
| 144 |
|
|
| 145 |
\section{Illustrations of the model in action} |
\section{Illustrations of the model in action} |
| 146 |
|
|
| 147 |
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, |
| 148 |
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 |
| 149 |
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 |
| 150 |
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 |
| 156 |
described in detail in the documentation. |
described in detail in the documentation. |
| 157 |
|
|
| 158 |
\subsection{Global atmosphere: `Held-Suarez' benchmark} |
\subsection{Global atmosphere: `Held-Suarez' benchmark} |
| 159 |
|
\begin{rawhtml} |
| 160 |
|
<!-- CMIREDIR:atmospheric_example: --> |
| 161 |
|
\end{rawhtml} |
| 162 |
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A novel feature of MITgcm is its ability to simulate, using one basic algorithm, |
A novel feature of MITgcm is its ability to simulate, using one basic algorithm, |
| 166 |
both atmospheric and oceanographic flows at both small and large scales. |
both atmospheric and oceanographic flows at both small and large scales. |
| 167 |
|
|
| 168 |
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$mb$ |
| 169 |
temperature field obtained using the atmospheric isomorph of MITgcm run at |
temperature field obtained using the atmospheric isomorph of MITgcm run at |
| 170 |
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 |
| 171 |
(blue) and warm air along an equatorial band (red). Fully developed |
(blue) and warm air along an equatorial band (red). Fully developed |
| 172 |
baroclinic eddies spawned in the northern hemisphere storm track are |
baroclinic eddies spawned in the northern hemisphere storm track are |
| 173 |
evident. There are no mountains or land-sea contrast in this calculation, |
evident. There are no mountains or land-sea contrast in this calculation, |
| 177 |
there are no mountains or land-sea contrast. |
there are no mountains or land-sea contrast. |
| 178 |
|
|
| 179 |
%% CNHbegin |
%% CNHbegin |
| 180 |
\input{part1/cubic_eddies_figure} |
\input{s_overview/text/cubic_eddies_figure} |
| 181 |
%% CNHend |
%% CNHend |
| 182 |
|
|
| 183 |
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 |
| 193 |
latitude-longitude grid. Both grids are supported within the model. |
latitude-longitude grid. Both grids are supported within the model. |
| 194 |
|
|
| 195 |
%% CNHbegin |
%% CNHbegin |
| 196 |
\input{part1/hs_zave_u_figure} |
\input{s_overview/text/hs_zave_u_figure} |
| 197 |
%% CNHend |
%% CNHend |
| 198 |
|
|
| 199 |
\subsection{Ocean gyres} |
\subsection{Ocean gyres} |
| 200 |
|
\begin{rawhtml} |
| 201 |
|
<!-- CMIREDIR:oceanic_example: --> |
| 202 |
|
\end{rawhtml} |
| 203 |
|
\begin{rawhtml} |
| 204 |
|
<!-- CMIREDIR:ocean_gyres: --> |
| 205 |
|
\end{rawhtml} |
| 206 |
|
|
| 207 |
Baroclinic instability is a ubiquitous process in the ocean, as well as the |
Baroclinic instability is a ubiquitous process in the ocean, as well as the |
| 208 |
atmosphere. Ocean eddies play an important role in modifying the |
atmosphere. Ocean eddies play an important role in modifying the |
| 212 |
increased until the baroclinic instability process is resolved, numerical |
increased until the baroclinic instability process is resolved, numerical |
| 213 |
solutions of a different and much more realistic kind, can be obtained. |
solutions of a different and much more realistic kind, can be obtained. |
| 214 |
|
|
| 215 |
Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity |
Figure \ref{fig:ocean-gyres} shows the surface temperature and |
| 216 |
field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal |
velocity field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ |
| 217 |
resolution on a $lat-lon$ |
horizontal resolution on a \textit{lat-lon} grid in which the pole has |
| 218 |
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 |
| 219 |
(to avoid the converging of meridian in northern latitudes). 21 vertical |
converging of meridian in northern latitudes). 21 vertical levels are |
| 220 |
levels are used in the vertical with a `lopped cell' representation of |
used in the vertical with a `lopped cell' representation of |
| 221 |
topography. The development and propagation of anomalously warm and cold |
topography. The development and propagation of anomalously warm and |
| 222 |
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 |
| 223 |
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 |
| 224 |
visible. |
is also clearly visible. |
| 225 |
|
|
| 226 |
%% CNHbegin |
%% CNHbegin |
| 227 |
\input{part1/atl6_figure} |
\input{s_overview/text/atl6_figure} |
| 228 |
%% CNHend |
%% CNHend |
| 229 |
|
|
| 230 |
|
|
| 231 |
\subsection{Global ocean circulation} |
\subsection{Global ocean circulation} |
| 232 |
|
\begin{rawhtml} |
| 233 |
Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean currents at |
<!-- CMIREDIR:global_ocean_circulation: --> |
| 234 |
the surface of a 4$^{\circ }$ |
\end{rawhtml} |
| 235 |
global ocean model run with 15 vertical levels. Lopped cells are used to |
|
| 236 |
represent topography on a regular $lat-lon$ grid extending from 70$^{\circ |
Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean |
| 237 |
}N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with |
currents at the surface of a $4^{\circ }$ global ocean model run with |
| 238 |
mixed boundary conditions on temperature and salinity at the surface. The |
15 vertical levels. Lopped cells are used to represent topography on a |
| 239 |
transfer properties of ocean eddies, convection and mixing is parameterized |
regular \textit{lat-lon} grid extending from $70^{\circ }N$ to |
| 240 |
in this model. |
$70^{\circ }S$. The model is driven using monthly-mean winds with |
| 241 |
|
mixed boundary conditions on temperature and salinity at the surface. |
| 242 |
|
The transfer properties of ocean eddies, convection and mixing is |
| 243 |
|
parameterized in this model. |
| 244 |
|
|
| 245 |
Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning |
Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning |
| 246 |
circulation of the global ocean in Sverdrups. |
circulation of the global ocean in Sverdrups. |
| 247 |
|
|
| 248 |
%%CNHbegin |
%%CNHbegin |
| 249 |
\input{part1/global_circ_figure} |
\input{s_overview/text/global_circ_figure} |
| 250 |
%%CNHend |
%%CNHend |
| 251 |
|
|
| 252 |
\subsection{Convection and mixing over topography} |
\subsection{Convection and mixing over topography} |
| 253 |
|
\begin{rawhtml} |
| 254 |
|
<!-- CMIREDIR:mixing_over_topography: --> |
| 255 |
|
\end{rawhtml} |
| 256 |
|
|
| 257 |
|
|
| 258 |
Dense plumes generated by localized cooling on the continental shelf of the |
Dense plumes generated by localized cooling on the continental shelf of the |
| 259 |
ocean may be influenced by rotation when the deformation radius is smaller |
ocean may be influenced by rotation when the deformation radius is smaller |
| 269 |
instability of the along-slope current. |
instability of the along-slope current. |
| 270 |
|
|
| 271 |
%%CNHbegin |
%%CNHbegin |
| 272 |
\input{part1/convect_and_topo} |
\input{s_overview/text/convect_and_topo} |
| 273 |
%%CNHend |
%%CNHend |
| 274 |
|
|
| 275 |
\subsection{Boundary forced internal waves} |
\subsection{Boundary forced internal waves} |
| 276 |
|
\begin{rawhtml} |
| 277 |
|
<!-- CMIREDIR:boundary_forced_internal_waves: --> |
| 278 |
|
\end{rawhtml} |
| 279 |
|
|
| 280 |
The unique ability of MITgcm to treat non-hydrostatic dynamics in the |
The unique ability of MITgcm to treat non-hydrostatic dynamics in the |
| 281 |
presence of complex geometry makes it an ideal tool to study internal wave |
presence of complex geometry makes it an ideal tool to study internal wave |
| 291 |
nonhydrostatic dynamics. |
nonhydrostatic dynamics. |
| 292 |
|
|
| 293 |
%%CNHbegin |
%%CNHbegin |
| 294 |
\input{part1/boundary_forced_waves} |
\input{s_overview/text/boundary_forced_waves} |
| 295 |
%%CNHend |
%%CNHend |
| 296 |
|
|
| 297 |
\subsection{Parameter sensitivity using the adjoint of MITgcm} |
\subsection{Parameter sensitivity using the adjoint of MITgcm} |
| 298 |
|
\begin{rawhtml} |
| 299 |
|
<!-- CMIREDIR:parameter_sensitivity: --> |
| 300 |
|
\end{rawhtml} |
| 301 |
|
|
| 302 |
Forward and tangent linear counterparts of MITgcm are supported using an |
Forward and tangent linear counterparts of MITgcm are supported using an |
| 303 |
`automatic adjoint compiler'. These can be used in parameter sensitivity and |
`automatic adjoint compiler'. These can be used in parameter sensitivity and |
| 304 |
data assimilation studies. |
data assimilation studies. |
| 305 |
|
|
| 306 |
As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity} |
As one example of application of the MITgcm adjoint, Figure |
| 307 |
maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude |
\ref{fig:hf-sensitivity} maps the gradient $\frac{\partial J}{\partial |
| 308 |
of the overturning stream-function shown in figure \ref{fig:large-scale-circ} |
\mathcal{H}}$where $J$ is the magnitude of the overturning |
| 309 |
at 60$^{\circ }$N and $ |
stream-function shown in figure \ref{fig:large-scale-circ} at |
| 310 |
\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 |
| 311 |
a 100 year period. We see that $J$ is |
air-sea heat flux over a 100 year period. We see that $J$ is sensitive |
| 312 |
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 |
| 313 |
of deep water for the thermohaline circulations. This calculation also |
deep water for the thermohaline circulations. This calculation also |
| 314 |
yields sensitivities to all other model parameters. |
yields sensitivities to all other model parameters. |
| 315 |
|
|
| 316 |
%%CNHbegin |
%%CNHbegin |
| 317 |
\input{part1/adj_hf_ocean_figure} |
\input{s_overview/text/adj_hf_ocean_figure} |
| 318 |
%%CNHend |
%%CNHend |
| 319 |
|
|
| 320 |
\subsection{Global state estimation of the ocean} |
\subsection{Global state estimation of the ocean} |
| 321 |
|
\begin{rawhtml} |
| 322 |
|
<!-- CMIREDIR:global_state_estimation: --> |
| 323 |
|
\end{rawhtml} |
| 324 |
|
|
| 325 |
|
|
| 326 |
An important application of MITgcm is in state estimation of the global |
An important application of MITgcm is in state estimation of the global |
| 327 |
ocean circulation. An appropriately defined `cost function', which measures |
ocean circulation. An appropriately defined `cost function', which measures |
| 335 |
1992-1997. |
1992-1997. |
| 336 |
|
|
| 337 |
%% CNHbegin |
%% CNHbegin |
| 338 |
\input{part1/assim_figure} |
\input{s_overview/text/assim_figure} |
| 339 |
%% CNHend |
%% CNHend |
| 340 |
|
|
| 341 |
\subsection{Ocean biogeochemical cycles} |
\subsection{Ocean biogeochemical cycles} |
| 342 |
|
\begin{rawhtml} |
| 343 |
MITgcm is being used to study global biogeochemical cycles in the ocean. For |
<!-- CMIREDIR:ocean_biogeo_cycles: --> |
| 344 |
example one can study the effects of interannual changes in meteorological |
\end{rawhtml} |
| 345 |
forcing and upper ocean circulation on the fluxes of carbon dioxide and |
|
| 346 |
oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows |
MITgcm is being used to study global biogeochemical cycles in the |
| 347 |
the annual air-sea flux of oxygen and its relation to density outcrops in |
ocean. For example one can study the effects of interannual changes in |
| 348 |
the southern oceans from a single year of a global, interannually varying |
meteorological forcing and upper ocean circulation on the fluxes of |
| 349 |
simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution |
carbon dioxide and oxygen between the ocean and atmosphere. Figure |
| 350 |
telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown). |
\ref{fig:biogeo} shows the annual air-sea flux of oxygen and its |
| 351 |
|
relation to density outcrops in the southern oceans from a single year |
| 352 |
|
of a global, interannually varying simulation. The simulation is run |
| 353 |
|
at $1^{\circ}\times1^{\circ}$ resolution telescoping to |
| 354 |
|
$\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not |
| 355 |
|
shown). |
| 356 |
|
|
| 357 |
%%CNHbegin |
%%CNHbegin |
| 358 |
\input{part1/biogeo_figure} |
\input{s_overview/text/biogeo_figure} |
| 359 |
%%CNHend |
%%CNHend |
| 360 |
|
|
| 361 |
\subsection{Simulations of laboratory experiments} |
\subsection{Simulations of laboratory experiments} |
| 362 |
|
\begin{rawhtml} |
| 363 |
|
<!-- CMIREDIR:classroom_exp: --> |
| 364 |
|
\end{rawhtml} |
| 365 |
|
|
| 366 |
Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a |
Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a |
| 367 |
laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An |
laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An |
| 373 |
stratification of the ACC. |
stratification of the ACC. |
| 374 |
|
|
| 375 |
%%CNHbegin |
%%CNHbegin |
| 376 |
\input{part1/lab_figure} |
\input{s_overview/text/lab_figure} |
| 377 |
%%CNHend |
%%CNHend |
| 378 |
|
|
| 379 |
% $Header$ |
% $Header$ |
| 380 |
% $Name$ |
% $Name$ |
| 381 |
|
|
| 382 |
\section{Continuous equations in `r' coordinates} |
\section{Continuous equations in `r' coordinates} |
| 383 |
|
\begin{rawhtml} |
| 384 |
|
<!-- CMIREDIR:z-p_isomorphism: --> |
| 385 |
|
\end{rawhtml} |
| 386 |
|
|
| 387 |
To render atmosphere and ocean models from one dynamical core we exploit |
To render atmosphere and ocean models from one dynamical core we exploit |
| 388 |
`isomorphisms' between equation sets that govern the evolution of the |
`isomorphisms' between equation sets that govern the evolution of the |
| 396 |
\ref{fig:isomorphic-equations}). |
\ref{fig:isomorphic-equations}). |
| 397 |
|
|
| 398 |
%%CNHbegin |
%%CNHbegin |
| 399 |
\input{part1/zandpcoord_figure.tex} |
\input{s_overview/text/zandpcoord_figure.tex} |
| 400 |
%%CNHend |
%%CNHend |
| 401 |
|
|
| 402 |
The state of the fluid at any time is characterized by the distribution of |
The state of the fluid at any time is characterized by the distribution of |
| 410 |
see figure \ref{fig:zandp-vert-coord}. |
see figure \ref{fig:zandp-vert-coord}. |
| 411 |
|
|
| 412 |
%%CNHbegin |
%%CNHbegin |
| 413 |
\input{part1/vertcoord_figure.tex} |
\input{s_overview/text/vertcoord_figure.tex} |
| 414 |
%%CNHend |
%%CNHend |
| 415 |
|
|
| 416 |
\begin{equation*} |
\begin{equation} |
| 417 |
\frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}} |
\frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}} |
| 418 |
\right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}} |
\right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}} |
| 419 |
\text{ horizontal mtm} \label{eq:horizontal_mtm} |
\text{ horizontal mtm} \label{eq:horizontal_mtm} |
| 420 |
\end{equation*} |
\end{equation} |
| 421 |
|
|
| 422 |
\begin{equation} |
\begin{equation} |
| 423 |
\frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{ |
\frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{ |
| 615 |
atmosphere)} \label{eq:moving-bc-atmos} |
atmosphere)} \label{eq:moving-bc-atmos} |
| 616 |
\end{eqnarray} |
\end{eqnarray} |
| 617 |
|
|
| 618 |
Then the (hydrostatic form of) equations (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt}) |
Then the (hydrostatic form of) equations |
| 619 |
yields a consistent set of atmospheric equations which, for convenience, are written out in $p$ |
(\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt}) yields a consistent |
| 620 |
coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}). |
set of atmospheric equations which, for convenience, are written out |
| 621 |
|
in $p$ coordinates in Appendix Atmosphere - see |
| 622 |
|
eqs(\ref{eq:atmos-prime}). |
| 623 |
|
|
| 624 |
\subsection{Ocean} |
\subsection{Ocean} |
| 625 |
|
|
| 661 |
|
|
| 662 |
\subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and |
\subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and |
| 663 |
Non-hydrostatic forms} |
Non-hydrostatic forms} |
| 664 |
|
\label{sec:all_hydrostatic_forms} |
| 665 |
|
\begin{rawhtml} |
| 666 |
|
<!-- CMIREDIR:non_hydrostatic: --> |
| 667 |
|
\end{rawhtml} |
| 668 |
|
|
| 669 |
|
|
| 670 |
Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms: |
Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms: |
| 671 |
|
|
| 673 |
\phi (x,y,r)=\phi _{s}(x,y)+\phi _{hyd}(x,y,r)+\phi _{nh}(x,y,r) |
\phi (x,y,r)=\phi _{s}(x,y)+\phi _{hyd}(x,y,r)+\phi _{nh}(x,y,r) |
| 674 |
\label{eq:phi-split} |
\label{eq:phi-split} |
| 675 |
\end{equation} |
\end{equation} |
| 676 |
and write eq(\ref{eq:incompressible}) in the form: |
%and write eq(\ref{eq:incompressible}) in the form: |
| 677 |
|
% ^- this eq is missing (jmc) ; replaced with: |
| 678 |
|
and write eq( \ref{eq:horizontal_mtm}) in the form: |
| 679 |
|
|
| 680 |
\begin{equation} |
\begin{equation} |
| 681 |
\frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi |
\frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi |
| 770 |
OPERATORS. |
OPERATORS. |
| 771 |
|
|
| 772 |
%%CNHbegin |
%%CNHbegin |
| 773 |
\input{part1/sphere_coord_figure.tex} |
\input{s_overview/text/sphere_coord_figure.tex} |
| 774 |
%%CNHend |
%%CNHend |
| 775 |
|
|
| 776 |
\subsubsection{Shallow atmosphere approximation} |
\subsubsection{Shallow atmosphere approximation} |
| 777 |
|
|
| 778 |
Most models are based on the `hydrostatic primitive equations' (HPE's) in |
Most models are based on the `hydrostatic primitive equations' (HPE's) |
| 779 |
which the vertical momentum equation is reduced to a statement of |
in which the vertical momentum equation is reduced to a statement of |
| 780 |
hydrostatic balance and the `traditional approximation' is made in which the |
hydrostatic balance and the `traditional approximation' is made in |
| 781 |
Coriolis force is treated approximately and the shallow atmosphere |
which the Coriolis force is treated approximately and the shallow |
| 782 |
approximation is made.\ The MITgcm need not make the `traditional |
atmosphere approximation is made. MITgcm need not make the |
| 783 |
approximation'. To be able to support consistent non-hydrostatic forms the |
`traditional approximation'. To be able to support consistent |
| 784 |
shallow atmosphere approximation can be relaxed - when dividing through by $ |
non-hydrostatic forms the shallow atmosphere approximation can be |
| 785 |
r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, |
relaxed - when dividing through by $ r $ in, for example, |
| 786 |
the radius of the earth. |
(\ref{eq:gu-speherical}), we do not replace $r$ by $a$, the radius of |
| 787 |
|
the earth. |
| 788 |
|
|
| 789 |
\subsubsection{Hydrostatic and quasi-hydrostatic forms} |
\subsubsection{Hydrostatic and quasi-hydrostatic forms} |
| 790 |
\label{sec:hydrostatic_and_quasi-hydrostatic_forms} |
\label{sec:hydrostatic_and_quasi-hydrostatic_forms} |
| 821 |
|
|
| 822 |
\subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} |
\subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} |
| 823 |
|
|
| 824 |
The MIT model presently supports a full non-hydrostatic ocean isomorph, but |
MITgcm presently supports a full non-hydrostatic ocean isomorph, but |
| 825 |
only a quasi-non-hydrostatic atmospheric isomorph. |
only a quasi-non-hydrostatic atmospheric isomorph. |
| 826 |
|
|
| 827 |
\paragraph{Non-hydrostatic Ocean} |
\paragraph{Non-hydrostatic Ocean} |
| 891 |
stepping forward the vertical momentum equation. |
stepping forward the vertical momentum equation. |
| 892 |
|
|
| 893 |
%%CNHbegin |
%%CNHbegin |
| 894 |
\input{part1/solution_strategy_figure.tex} |
\input{s_overview/text/solution_strategy_figure.tex} |
| 895 |
%%CNHend |
%%CNHend |
| 896 |
|
|
| 897 |
There is no penalty in implementing \textbf{QH} over \textbf{HPE} except, of |
There is no penalty in implementing \textbf{QH} over \textbf{HPE} except, of |
| 1080 |
|
|
| 1081 |
The mixing terms for the temperature and salinity equations have a similar |
The mixing terms for the temperature and salinity equations have a similar |
| 1082 |
form to that of momentum except that the diffusion tensor can be |
form to that of momentum except that the diffusion tensor can be |
| 1083 |
non-diagonal and have varying coefficients. $\qquad $ |
non-diagonal and have varying coefficients. |
| 1084 |
\begin{equation} |
\begin{equation} |
| 1085 |
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 |
| 1086 |
_{h}^{4}(T,S) \label{eq:diffusion} |
_{h}^{4}(T,S) \label{eq:diffusion} |
| 1106 |
|
|
| 1107 |
\subsection{Vector invariant form} |
\subsection{Vector invariant form} |
| 1108 |
|
|
| 1109 |
For some purposes it is advantageous to write momentum advection in eq(\ref |
For some purposes it is advantageous to write momentum advection in |
| 1110 |
{eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the (so-called) `vector invariant' form: |
eq(\ref {eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the |
| 1111 |
|
(so-called) `vector invariant' form: |
| 1112 |
|
|
| 1113 |
\begin{equation} |
\begin{equation} |
| 1114 |
\frac{D\vec{\mathbf{v}}}{Dt}=\frac{\partial \vec{\mathbf{v}}}{\partial t} |
\frac{D\vec{\mathbf{v}}}{Dt}=\frac{\partial \vec{\mathbf{v}}}{\partial t} |
| 1219 |
surface ($\phi $ is imposed and $\omega \neq 0$). |
surface ($\phi $ is imposed and $\omega \neq 0$). |
| 1220 |
|
|
| 1221 |
\subsubsection{Splitting the geo-potential} |
\subsubsection{Splitting the geo-potential} |
| 1222 |
|
\label{sec:hpe-p-geo-potential-split} |
| 1223 |
|
|
| 1224 |
For the purposes of initialization and reducing round-off errors, the model |
For the purposes of initialization and reducing round-off errors, the model |
| 1225 |
deals with perturbations from reference (or ``standard'') profiles. For |
deals with perturbations from reference (or ``standard'') profiles. For |
| 1249 |
The final form of the HPE's in p coordinates is then: |
The final form of the HPE's in p coordinates is then: |
| 1250 |
\begin{eqnarray} |
\begin{eqnarray} |
| 1251 |
\frac{D\vec{\mathbf{v}}_{h}}{Dt}+f\hat{\mathbf{k}}\times \vec{\mathbf{v}} |
\frac{D\vec{\mathbf{v}}_{h}}{Dt}+f\hat{\mathbf{k}}\times \vec{\mathbf{v}} |
| 1252 |
_{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \label{eq:atmos-prime} \\ |
_{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} |
| 1253 |
|
\label{eq:atmos-prime} \\ |
| 1254 |
\frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\ |
\frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\ |
| 1255 |
\mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{ |
\mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{ |
| 1256 |
\partial p} &=&0 \\ |
\partial p} &=&0 \\ |
| 1296 |
_{\theta ,S}\frac{Dp}{Dt} \label{EOSexpansion} |
_{\theta ,S}\frac{Dp}{Dt} \label{EOSexpansion} |
| 1297 |
\end{equation} |
\end{equation} |
| 1298 |
|
|
| 1299 |
Note that $\frac{\partial \rho }{\partial p}=\frac{1}{c_{s}^{2}}$ is the |
Note that $\frac{\partial \rho }{\partial p}=\frac{1}{c_{s}^{2}}$ is |
| 1300 |
reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref{eq-zns-cont} gives: |
the reciprocal of the sound speed ($c_{s}$) squared. Substituting into |
| 1301 |
|
\ref{eq-zns-cont} gives: |
| 1302 |
\begin{equation} |
\begin{equation} |
| 1303 |
\frac{1}{\rho c_{s}^{2}}\frac{Dp}{Dt}+\mathbf{\nabla }_{z}\cdot \vec{\mathbf{ |
\frac{1}{\rho c_{s}^{2}}\frac{Dp}{Dt}+\mathbf{\nabla }_{z}\cdot \vec{\mathbf{ |
| 1304 |
v}}+\partial _{z}w\approx 0 \label{eq-zns-pressure} |
v}}+\partial _{z}w\approx 0 \label{eq-zns-pressure} |
| 1492 |
\end{equation*} |
\end{equation*} |
| 1493 |
|
|
| 1494 |
\begin{equation*} |
\begin{equation*} |
| 1495 |
v=r\frac{D\varphi }{Dt}\qquad |
v=r\frac{D\varphi }{Dt} |
| 1496 |
\end{equation*} |
\end{equation*} |
|
$\qquad \qquad \qquad \qquad $ |
|
| 1497 |
|
|
| 1498 |
\begin{equation*} |
\begin{equation*} |
| 1499 |
\dot{r}=\frac{Dr}{Dt} |
\dot{r}=\frac{Dr}{Dt} |
| 1503 |
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 |
| 1504 |
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. |
| 1505 |
|
|
| 1506 |
The `grad' ($\nabla $) and `div' ($\nabla $.) operators are defined by, in |
The `grad' ($\nabla $) and `div' ($\nabla\cdot$) operators are defined by, in |
| 1507 |
spherical coordinates: |
spherical coordinates: |
| 1508 |
|
|
| 1509 |
\begin{equation*} |
\begin{equation*} |
| 1513 |
\end{equation*} |
\end{equation*} |
| 1514 |
|
|
| 1515 |
\begin{equation*} |
\begin{equation*} |
| 1516 |
\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 |
| 1517 |
\lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} |
\lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} |
| 1518 |
+\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} |
| 1519 |
\end{equation*} |
\end{equation*} |