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% Section: Overview |
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This document provides the reader with the information necessary to |
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\section{Introduction} |
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This documentation provides the reader with the information necessary to |
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carry out numerical experiments using MITgcm. It gives a comprehensive |
carry out numerical experiments using MITgcm. It gives a comprehensive |
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description of the continuous equations on which the model is based, the |
description of the continuous equations on which the model is based, the |
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numerical algorithms the model employs and a description of the associated |
numerical algorithms the model employs and a description of the associated |
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both process and general circulation studies of the atmosphere and ocean are |
both process and general circulation studies of the atmosphere and ocean are |
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also presented. |
also presented. |
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\section{Introduction} |
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MITgcm has a number of novel aspects: |
MITgcm has a number of novel aspects: |
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\begin{itemize} |
\begin{itemize} |
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models - see fig \ref{fig:onemodel} |
models - see fig \ref{fig:onemodel} |
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\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 |
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small-scale and large scale processes - see fig \ref{fig:all-scales} |
small-scale and large scale processes - see fig \ref{fig:all-scales} |
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\item finite volume techniques are employed yielding an intuitive |
\item finite volume techniques are employed yielding an intuitive |
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orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes} |
orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes} |
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\input{part1/fvol_figure} |
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\item tangent linear and adjoint counterparts are automatically maintained |
\item tangent linear and adjoint counterparts are automatically maintained |
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computational platforms. |
computational platforms. |
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\end{itemize} |
\end{itemize} |
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Key publications reporting on and charting the development of the model are: |
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\begin{verbatim} |
Key publications reporting on and charting the development of the model are |
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\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} |
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(an overview on the model formulation can also be found in \cite{adcroft:04c}): |
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\begin{verbatim} |
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Hill, C. and J. Marshall, (1995) |
Hill, C. and J. Marshall, (1995) |
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Application of a Parallel Navier-Stokes Model to Ocean Circulation in |
Application of a Parallel Navier-Stokes Model to Ocean Circulation in |
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Parallel Computational Fluid Dynamics |
Parallel Computational Fluid Dynamics |
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Elsevier Science B.V.: New York |
Elsevier Science B.V.: New York |
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Marshall, J., C. Hill, L. Perelman, and A. Adcroft, (1997) |
Marshall, J., C. Hill, L. Perelman, and A. Adcroft, (1997) |
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Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling, |
Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling |
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J. Geophysical Res., 102(C3), 5733-5752. |
J. Geophysical Res., 102(C3), 5733-5752. |
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Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, (1997) |
Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, (1997) |
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Hill, C, Adcroft,A., Jamous,D., and J. Marshall, (1999) |
Hill, C, Adcroft,A., Jamous,D., and J. Marshall, (1999) |
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A Strategy for Terascale Climate Modeling. |
A Strategy for Terascale Climate Modeling. |
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In Proceedings of the Eight ECMWF Workshop on the Use of Parallel Processors |
In Proceedings of the Eighth ECMWF Workshop on the Use of Parallel Processors |
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in Meteorology |
in Meteorology, pages 406-425 |
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World Scientific Publishing Co: UK |
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Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999) |
Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999) |
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Construction of the adjoint MIT ocean general circulation model and |
Construction of the adjoint MIT ocean general circulation model and |
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application to Atlantic heat transport variability |
application to Atlantic heat transport variability |
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J. Geophysical Res., 104(C12), 29,529-29,547. |
J. Geophysical Res., 104(C12), 29,529-29,547. |
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\end{verbatim} |
\end{verbatim} |
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We begin by briefly showing some of the results of the model in action to |
We begin by briefly showing some of the results of the model in action to |
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give a feel for the wide range of problems that can be addressed using it. |
give a feel for the wide range of problems that can be addressed using it. |
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\section{Illustrations of the model in action} |
\section{Illustrations of the model in action} |
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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, |
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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 |
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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 |
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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 |
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described in detail in the documentation. |
described in detail in the documentation. |
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\subsection{Global atmosphere: `Held-Suarez' benchmark} |
\subsection{Global atmosphere: `Held-Suarez' benchmark} |
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\begin{rawhtml} |
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<!-- CMIREDIR:atmospheric_example: --> |
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\end{rawhtml} |
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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, |
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both atmospheric and oceanographic flows at both small and large scales. |
both atmospheric and oceanographic flows at both small and large scales. |
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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$mb$ |
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temperature field obtained using the atmospheric isomorph of MITgcm run at |
temperature field obtained using the atmospheric isomorph of MITgcm run at |
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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 |
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(blue) and warm air along an equatorial band (red). Fully developed |
(blue) and warm air along an equatorial band (red). Fully developed |
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baroclinic eddies spawned in the northern hemisphere storm track are |
baroclinic eddies spawned in the northern hemisphere storm track are |
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evident. There are no mountains or land-sea contrast in this calculation, |
evident. There are no mountains or land-sea contrast in this calculation, |
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there are no mountains or land-sea contrast. |
there are no mountains or land-sea contrast. |
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%% CNHbegin |
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\input{part1/cubic_eddies_figure} |
\input{s_overview/text/cubic_eddies_figure} |
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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 |
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latitude-longitude grid. Both grids are supported within the model. |
latitude-longitude grid. Both grids are supported within the model. |
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%% CNHbegin |
%% CNHbegin |
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\input{part1/hs_zave_u_figure} |
\input{s_overview/text/hs_zave_u_figure} |
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\subsection{Ocean gyres} |
\subsection{Ocean gyres} |
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\begin{rawhtml} |
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<!-- CMIREDIR:oceanic_example: --> |
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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 |
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atmosphere. Ocean eddies play an important role in modifying the |
atmosphere. Ocean eddies play an important role in modifying the |
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increased until the baroclinic instability process is resolved, numerical |
increased until the baroclinic instability process is resolved, numerical |
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solutions of a different and much more realistic kind, can be obtained. |
solutions of a different and much more realistic kind, can be obtained. |
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Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity |
Figure \ref{fig:ocean-gyres} shows the surface temperature and |
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field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal |
velocity field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ |
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resolution on a $lat-lon$ |
horizontal resolution on a \textit{lat-lon} grid in which the pole has |
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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 |
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(to avoid the converging of meridian in northern latitudes). 21 vertical |
converging of meridian in northern latitudes). 21 vertical levels are |
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levels are used in the vertical with a `lopped cell' representation of |
used in the vertical with a `lopped cell' representation of |
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topography. The development and propagation of anomalously warm and cold |
topography. The development and propagation of anomalously warm and |
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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 |
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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 |
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visible. |
is also clearly visible. |
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%% CNHbegin |
%% CNHbegin |
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\input{part1/atl6_figure} |
\input{s_overview/text/atl6_figure} |
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%% CNHend |
%% CNHend |
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\subsection{Global ocean circulation} |
\subsection{Global ocean circulation} |
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\begin{rawhtml} |
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Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean currents at |
<!-- CMIREDIR:global_ocean_circulation: --> |
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the surface of a 4$^{\circ }$ |
\end{rawhtml} |
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global ocean model run with 15 vertical levels. Lopped cells are used to |
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represent topography on a regular $lat-lon$ grid extending from 70$^{\circ |
Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean |
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}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 |
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mixed boundary conditions on temperature and salinity at the surface. The |
15 vertical levels. Lopped cells are used to represent topography on a |
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transfer properties of ocean eddies, convection and mixing is parameterized |
regular \textit{lat-lon} grid extending from $70^{\circ }N$ to |
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in this model. |
$70^{\circ }S$. The model is driven using monthly-mean winds with |
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mixed boundary conditions on temperature and salinity at the surface. |
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The transfer properties of ocean eddies, convection and mixing is |
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parameterized in this model. |
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Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning |
Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning |
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circulation of the global ocean in Sverdrups. |
circulation of the global ocean in Sverdrups. |
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\input{part1/global_circ_figure} |
\input{s_overview/text/global_circ_figure} |
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\subsection{Convection and mixing over topography} |
\subsection{Convection and mixing over topography} |
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\begin{rawhtml} |
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<!-- CMIREDIR:mixing_over_topography: --> |
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\end{rawhtml} |
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Dense plumes generated by localized cooling on the continental shelf of the |
Dense plumes generated by localized cooling on the continental shelf of the |
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ocean may be influenced by rotation when the deformation radius is smaller |
ocean may be influenced by rotation when the deformation radius is smaller |
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instability of the along-slope current. |
instability of the along-slope current. |
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\input{part1/convect_and_topo} |
\input{s_overview/text/convect_and_topo} |
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\subsection{Boundary forced internal waves} |
\subsection{Boundary forced internal waves} |
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\begin{rawhtml} |
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<!-- CMIREDIR:boundary_forced_internal_waves: --> |
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\end{rawhtml} |
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The unique ability of MITgcm to treat non-hydrostatic dynamics in the |
The unique ability of MITgcm to treat non-hydrostatic dynamics in the |
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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 |
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nonhydrostatic dynamics. |
nonhydrostatic dynamics. |
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%%CNHbegin |
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\input{part1/boundary_forced_waves} |
\input{s_overview/text/boundary_forced_waves} |
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\subsection{Parameter sensitivity using the adjoint of MITgcm} |
\subsection{Parameter sensitivity using the adjoint of MITgcm} |
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\begin{rawhtml} |
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<!-- CMIREDIR:parameter_sensitivity: --> |
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\end{rawhtml} |
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Forward and tangent linear counterparts of MITgcm are supported using an |
Forward and tangent linear counterparts of MITgcm are supported using an |
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`automatic adjoint compiler'. These can be used in parameter sensitivity and |
`automatic adjoint compiler'. These can be used in parameter sensitivity and |
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data assimilation studies. |
data assimilation studies. |
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As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity} |
As one example of application of the MITgcm adjoint, Figure |
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maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude |
\ref{fig:hf-sensitivity} maps the gradient $\frac{\partial J}{\partial |
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of the overturning stream-function shown in figure \ref{fig:large-scale-circ} |
\mathcal{H}}$where $J$ is the magnitude of the overturning |
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at 60$^{\circ }$N and $ |
stream-function shown in figure \ref{fig:large-scale-circ} at |
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\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 |
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a 100 year period. We see that $J$ is |
air-sea heat flux over a 100 year period. We see that $J$ is sensitive |
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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 |
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of deep water for the thermohaline circulations. This calculation also |
deep water for the thermohaline circulations. This calculation also |
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yields sensitivities to all other model parameters. |
yields sensitivities to all other model parameters. |
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%%CNHbegin |
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\input{part1/adj_hf_ocean_figure} |
\input{s_overview/text/adj_hf_ocean_figure} |
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\subsection{Global state estimation of the ocean} |
\subsection{Global state estimation of the ocean} |
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\begin{rawhtml} |
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<!-- CMIREDIR:global_state_estimation: --> |
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\end{rawhtml} |
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An important application of MITgcm is in state estimation of the global |
An important application of MITgcm is in state estimation of the global |
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ocean circulation. An appropriately defined `cost function', which measures |
ocean circulation. An appropriately defined `cost function', which measures |
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the departure of the model from observations (both remotely sensed and |
the departure of the model from observations (both remotely sensed and |
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in-situ) over an interval of time, is minimized by adjusting `control |
in-situ) over an interval of time, is minimized by adjusting `control |
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parameters' such as air-sea fluxes, the wind field, the initial conditions |
parameters' such as air-sea fluxes, the wind field, the initial conditions |
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etc. Figure \ref{fig:assimilated-globes} shows an estimate of the time-mean |
etc. Figure \ref{fig:assimilated-globes} shows the large scale planetary |
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surface elevation of the ocean obtained by bringing the model in to |
circulation and a Hopf-Muller plot of Equatorial sea-surface height. |
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Both are obtained from assimilation bringing the model in to |
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consistency with altimetric and in-situ observations over the period |
consistency with altimetric and in-situ observations over the period |
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1992-1997. {\bf CHANGE THIS TEXT - FIG FROM PATRICK/CARL/DETLEF} |
1992-1997. |
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%% CNHbegin |
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\input{part1/assim_figure} |
\input{s_overview/text/assim_figure} |
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%% CNHend |
%% CNHend |
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\subsection{Ocean biogeochemical cycles} |
\subsection{Ocean biogeochemical cycles} |
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\begin{rawhtml} |
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MITgcm is being used to study global biogeochemical cycles in the ocean. For |
<!-- CMIREDIR:ocean_biogeo_cycles: --> |
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example one can study the effects of interannual changes in meteorological |
\end{rawhtml} |
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forcing and upper ocean circulation on the fluxes of carbon dioxide and |
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oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows |
MITgcm is being used to study global biogeochemical cycles in the |
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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 |
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the southern oceans from a single year of a global, interannually varying |
meteorological forcing and upper ocean circulation on the fluxes of |
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simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution |
carbon dioxide and oxygen between the ocean and atmosphere. Figure |
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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 |
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relation to density outcrops in the southern oceans from a single year |
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of a global, interannually varying simulation. The simulation is run |
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at $1^{\circ}\times1^{\circ}$ resolution telescoping to |
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$\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not |
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shown). |
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%%CNHbegin |
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\input{part1/biogeo_figure} |
\input{s_overview/text/biogeo_figure} |
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\subsection{Simulations of laboratory experiments} |
\subsection{Simulations of laboratory experiments} |
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\begin{rawhtml} |
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<!-- CMIREDIR:classroom_exp: --> |
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\end{rawhtml} |
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Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a |
Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a |
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laboratory experiment inquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An |
laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An |
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initially homogeneous tank of water ($1m$ in diameter) is driven from its |
initially homogeneous tank of water ($1m$ in diameter) is driven from its |
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free surface by a rotating heated disk. The combined action of mechanical |
free surface by a rotating heated disk. The combined action of mechanical |
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and thermal forcing creates a lens of fluid which becomes baroclinically |
and thermal forcing creates a lens of fluid which becomes baroclinically |
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stratification of the ACC. |
stratification of the ACC. |
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%%CNHbegin |
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\input{part1/lab_figure} |
\input{s_overview/text/lab_figure} |
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% $Header$ |
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% $Name$ |
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\section{Continuous equations in `r' coordinates} |
\section{Continuous equations in `r' coordinates} |
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\begin{rawhtml} |
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<!-- CMIREDIR:z-p_isomorphism: --> |
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\end{rawhtml} |
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To render atmosphere and ocean models from one dynamical core we exploit |
To render atmosphere and ocean models from one dynamical core we exploit |
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`isomorphisms' between equation sets that govern the evolution of the |
`isomorphisms' between equation sets that govern the evolution of the |
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and encoded. The model variables have different interpretations depending on |
and encoded. The model variables have different interpretations depending on |
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whether the atmosphere or ocean is being studied. Thus, for example, the |
whether the atmosphere or ocean is being studied. Thus, for example, the |
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vertical coordinate `$r$' is interpreted as pressure, $p$, if we are |
vertical coordinate `$r$' is interpreted as pressure, $p$, if we are |
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modeling the atmosphere (left hand side of figure \ref{fig:isomorphic-equations}) |
modeling the atmosphere (right hand side of figure \ref{fig:isomorphic-equations}) |
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and height, $z$, if we are modeling the ocean (right hand side of figure |
and height, $z$, if we are modeling the ocean (left hand side of figure |
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\ref{fig:isomorphic-equations}). |
\ref{fig:isomorphic-equations}). |
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%%CNHbegin |
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\input{part1/zandpcoord_figure.tex} |
\input{s_overview/text/zandpcoord_figure.tex} |
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%%CNHend |
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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 |
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see figure \ref{fig:zandp-vert-coord}. |
see figure \ref{fig:zandp-vert-coord}. |
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%%CNHbegin |
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\input{part1/vertcoord_figure.tex} |
\input{s_overview/text/vertcoord_figure.tex} |
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%%CNHend |
%%CNHend |
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\begin{equation*} |
\begin{equation} |
408 |
\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}} |
409 |
\right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}} |
\right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}} |
410 |
\text{ horizontal mtm} \label{eq:horizontal_mtm} |
\text{ horizontal mtm} \label{eq:horizontal_mtm} |
411 |
\end{equation*} |
\end{equation} |
412 |
|
|
413 |
\begin{equation} |
\begin{equation} |
414 |
\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{ |
507 |
at fixed and moving $r$ surfaces we set (see figure \ref{fig:zandp-vert-coord}): |
at fixed and moving $r$ surfaces we set (see figure \ref{fig:zandp-vert-coord}): |
508 |
|
|
509 |
\begin{equation} |
\begin{equation} |
510 |
\dot{r}=0atr=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)} |
\dot{r}=0 \text{\ at\ } r=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)} |
511 |
\label{eq:fixedbc} |
\label{eq:fixedbc} |
512 |
\end{equation} |
\end{equation} |
513 |
|
|
514 |
\begin{equation} |
\begin{equation} |
515 |
\dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \ |
\dot{r}=\frac{Dr}{Dt} \text{\ at\ } r=R_{moving}\text{ \ |
516 |
(ocean surface,bottom of the atmosphere)} \label{eq:movingbc} |
(ocean surface,bottom of the atmosphere)} \label{eq:movingbc} |
517 |
\end{equation} |
\end{equation} |
518 |
|
|
606 |
atmosphere)} \label{eq:moving-bc-atmos} |
atmosphere)} \label{eq:moving-bc-atmos} |
607 |
\end{eqnarray} |
\end{eqnarray} |
608 |
|
|
609 |
Then the (hydrostatic form of) equations (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt}) |
Then the (hydrostatic form of) equations |
610 |
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 |
611 |
coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}). |
set of atmospheric equations which, for convenience, are written out |
612 |
|
in $p$ coordinates in Appendix Atmosphere - see |
613 |
|
eqs(\ref{eq:atmos-prime}). |
614 |
|
|
615 |
\subsection{Ocean} |
\subsection{Ocean} |
616 |
|
|
652 |
|
|
653 |
\subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and |
\subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and |
654 |
Non-hydrostatic forms} |
Non-hydrostatic forms} |
655 |
|
\label{sec:all_hydrostatic_forms} |
656 |
|
\begin{rawhtml} |
657 |
|
<!-- CMIREDIR:non_hydrostatic: --> |
658 |
|
\end{rawhtml} |
659 |
|
|
660 |
|
|
661 |
Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms: |
Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms: |
662 |
|
|
664 |
\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) |
665 |
\label{eq:phi-split} |
\label{eq:phi-split} |
666 |
\end{equation} |
\end{equation} |
667 |
and write eq(\ref{eq:incompressible}) in the form: |
%and write eq(\ref{eq:incompressible}) in the form: |
668 |
|
% ^- this eq is missing (jmc) ; replaced with: |
669 |
|
and write eq( \ref{eq:horizontal_mtm}) in the form: |
670 |
|
|
671 |
\begin{equation} |
\begin{equation} |
672 |
\frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi |
\frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi |
761 |
OPERATORS. |
OPERATORS. |
762 |
|
|
763 |
%%CNHbegin |
%%CNHbegin |
764 |
\input{part1/sphere_coord_figure.tex} |
\input{s_overview/text/sphere_coord_figure.tex} |
765 |
%%CNHend |
%%CNHend |
766 |
|
|
767 |
\subsubsection{Shallow atmosphere approximation} |
\subsubsection{Shallow atmosphere approximation} |
768 |
|
|
769 |
Most models are based on the `hydrostatic primitive equations' (HPE's) in |
Most models are based on the `hydrostatic primitive equations' (HPE's) |
770 |
which the vertical momentum equation is reduced to a statement of |
in which the vertical momentum equation is reduced to a statement of |
771 |
hydrostatic balance and the `traditional approximation' is made in which the |
hydrostatic balance and the `traditional approximation' is made in |
772 |
Coriolis force is treated approximately and the shallow atmosphere |
which the Coriolis force is treated approximately and the shallow |
773 |
approximation is made.\ The MITgcm need not make the `traditional |
atmosphere approximation is made. MITgcm need not make the |
774 |
approximation'. To be able to support consistent non-hydrostatic forms the |
`traditional approximation'. To be able to support consistent |
775 |
shallow atmosphere approximation can be relaxed - when dividing through by $ |
non-hydrostatic forms the shallow atmosphere approximation can be |
776 |
r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, |
relaxed - when dividing through by $ r $ in, for example, |
777 |
the radius of the earth. |
(\ref{eq:gu-speherical}), we do not replace $r$ by $a$, the radius of |
778 |
|
the earth. |
779 |
|
|
780 |
\subsubsection{Hydrostatic and quasi-hydrostatic forms} |
\subsubsection{Hydrostatic and quasi-hydrostatic forms} |
781 |
\label{sec:hydrostatic_and_quasi-hydrostatic_forms} |
\label{sec:hydrostatic_and_quasi-hydrostatic_forms} |
812 |
|
|
813 |
\subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} |
\subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} |
814 |
|
|
815 |
The MIT model presently supports a full non-hydrostatic ocean isomorph, but |
MITgcm presently supports a full non-hydrostatic ocean isomorph, but |
816 |
only a quasi-non-hydrostatic atmospheric isomorph. |
only a quasi-non-hydrostatic atmospheric isomorph. |
817 |
|
|
818 |
\paragraph{Non-hydrostatic Ocean} |
\paragraph{Non-hydrostatic Ocean} |
882 |
stepping forward the vertical momentum equation. |
stepping forward the vertical momentum equation. |
883 |
|
|
884 |
%%CNHbegin |
%%CNHbegin |
885 |
\input{part1/solution_strategy_figure.tex} |
\input{s_overview/text/solution_strategy_figure.tex} |
886 |
%%CNHend |
%%CNHend |
887 |
|
|
888 |
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 |
1071 |
|
|
1072 |
The mixing terms for the temperature and salinity equations have a similar |
The mixing terms for the temperature and salinity equations have a similar |
1073 |
form to that of momentum except that the diffusion tensor can be |
form to that of momentum except that the diffusion tensor can be |
1074 |
non-diagonal and have varying coefficients. $\qquad $ |
non-diagonal and have varying coefficients. |
1075 |
\begin{equation} |
\begin{equation} |
1076 |
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 |
1077 |
_{h}^{4}(T,S) \label{eq:diffusion} |
_{h}^{4}(T,S) \label{eq:diffusion} |
1097 |
|
|
1098 |
\subsection{Vector invariant form} |
\subsection{Vector invariant form} |
1099 |
|
|
1100 |
For some purposes it is advantageous to write momentum advection in eq(\ref |
For some purposes it is advantageous to write momentum advection in |
1101 |
{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 |
1102 |
|
(so-called) `vector invariant' form: |
1103 |
|
|
1104 |
\begin{equation} |
\begin{equation} |
1105 |
\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} |
1120 |
Tangent linear and adjoint counterparts of the forward model are described |
Tangent linear and adjoint counterparts of the forward model are described |
1121 |
in Chapter 5. |
in Chapter 5. |
1122 |
|
|
|
% $Header$ |
|
|
% $Name$ |
|
|
|
|
1123 |
\section{Appendix ATMOSPHERE} |
\section{Appendix ATMOSPHERE} |
1124 |
|
|
1125 |
\subsection{Hydrostatic Primitive Equations for the Atmosphere in pressure |
\subsection{Hydrostatic Primitive Equations for the Atmosphere in pressure |
1139 |
c_{v}\frac{DT}{Dt}+p\frac{D\alpha }{Dt} &=&\mathcal{Q} \label{eq:atmos-heat} |
c_{v}\frac{DT}{Dt}+p\frac{D\alpha }{Dt} &=&\mathcal{Q} \label{eq:atmos-heat} |
1140 |
\end{eqnarray} |
\end{eqnarray} |
1141 |
where $\vec{\mathbf{v}}_{h}=(u,v,0)$ is the `horizontal' (on pressure |
where $\vec{\mathbf{v}}_{h}=(u,v,0)$ is the `horizontal' (on pressure |
1142 |
surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot |
surfaces) component of velocity, $\frac{D}{Dt}=\frac{\partial}{\partial t} |
1143 |
\mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total |
+\vec{\mathbf{v}}_{h}\cdot \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ |
1144 |
derivative, $f=2\Omega \sin \varphi$ is the Coriolis parameter, $\phi =gz$ is |
is the total derivative, $f=2\Omega \sin \varphi$ is the Coriolis parameter, |
1145 |
the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp |
$\phi =gz$ is the geopotential, $\alpha =1/\rho $ is the specific volume, |
1146 |
}{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref |
$\omega =\frac{Dp }{Dt}$ is the vertical velocity in the $p-$coordinate. |
1147 |
{eq:atmos-heat}) is the first law of thermodynamics where internal energy $ |
Equation(\ref {eq:atmos-heat}) is the first law of thermodynamics where internal |
1148 |
e=c_{v}T$, $T$ is temperature, $Q$ is the rate of heating per unit mass and $ |
energy $e=c_{v}T$, $T$ is temperature, $Q$ is the rate of heating per unit mass |
1149 |
p\frac{D\alpha }{Dt}$ is the work done by the fluid in compressing. |
and $p\frac{D\alpha }{Dt}$ is the work done by the fluid in compressing. |
1150 |
|
|
1151 |
It is convenient to cast the heat equation in terms of potential temperature |
It is convenient to cast the heat equation in terms of potential temperature |
1152 |
$\theta $ so that it looks more like a generic conservation law. |
$\theta $ so that it looks more like a generic conservation law. |
1207 |
surface ($\phi $ is imposed and $\omega \neq 0$). |
surface ($\phi $ is imposed and $\omega \neq 0$). |
1208 |
|
|
1209 |
\subsubsection{Splitting the geo-potential} |
\subsubsection{Splitting the geo-potential} |
1210 |
|
\label{sec:hpe-p-geo-potential-split} |
1211 |
|
|
1212 |
For the purposes of initialization and reducing round-off errors, the model |
For the purposes of initialization and reducing round-off errors, the model |
1213 |
deals with perturbations from reference (or ``standard'') profiles. For |
deals with perturbations from reference (or ``standard'') profiles. For |
1237 |
The final form of the HPE's in p coordinates is then: |
The final form of the HPE's in p coordinates is then: |
1238 |
\begin{eqnarray} |
\begin{eqnarray} |
1239 |
\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}} |
1240 |
_{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \label{eq:atmos-prime} \\ |
_{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} |
1241 |
|
\label{eq:atmos-prime} \\ |
1242 |
\frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\ |
\frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\ |
1243 |
\mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{ |
\mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{ |
1244 |
\partial p} &=&0 \\ |
\partial p} &=&0 \\ |
1246 |
\frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi } |
\frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi } |
1247 |
\end{eqnarray} |
\end{eqnarray} |
1248 |
|
|
|
% $Header$ |
|
|
% $Name$ |
|
|
|
|
1249 |
\section{Appendix OCEAN} |
\section{Appendix OCEAN} |
1250 |
|
|
1251 |
\subsection{Equations of motion for the ocean} |
\subsection{Equations of motion for the ocean} |
1281 |
_{\theta ,S}\frac{Dp}{Dt} \label{EOSexpansion} |
_{\theta ,S}\frac{Dp}{Dt} \label{EOSexpansion} |
1282 |
\end{equation} |
\end{equation} |
1283 |
|
|
1284 |
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 |
1285 |
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 |
1286 |
|
\ref{eq-zns-cont} gives: |
1287 |
\begin{equation} |
\begin{equation} |
1288 |
\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{ |
1289 |
v}}+\partial _{z}w\approx 0 \label{eq-zns-pressure} |
v}}+\partial _{z}w\approx 0 \label{eq-zns-pressure} |
1460 |
_{nh}=0$ form of these equations that are used throughout the ocean modeling |
_{nh}=0$ form of these equations that are used throughout the ocean modeling |
1461 |
community and referred to as the primitive equations (HPE). |
community and referred to as the primitive equations (HPE). |
1462 |
|
|
|
% $Header$ |
|
|
% $Name$ |
|
|
|
|
1463 |
\section{Appendix:OPERATORS} |
\section{Appendix:OPERATORS} |
1464 |
|
|
1465 |
\subsection{Coordinate systems} |
\subsection{Coordinate systems} |
1474 |
\end{equation*} |
\end{equation*} |
1475 |
|
|
1476 |
\begin{equation*} |
\begin{equation*} |
1477 |
v=r\frac{D\varphi }{Dt}\qquad |
v=r\frac{D\varphi }{Dt} |
1478 |
\end{equation*} |
\end{equation*} |
|
$\qquad \qquad \qquad \qquad $ |
|
1479 |
|
|
1480 |
\begin{equation*} |
\begin{equation*} |
1481 |
\dot{r}=\frac{Dr}{Dt} |
\dot{r}=\frac{Dr}{Dt} |
1485 |
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 |
1486 |
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. |
1487 |
|
|
1488 |
The `grad' ($\nabla $) and `div' ($\nabla $.) operators are defined by, in |
The `grad' ($\nabla $) and `div' ($\nabla\cdot$) operators are defined by, in |
1489 |
spherical coordinates: |
spherical coordinates: |
1490 |
|
|
1491 |
\begin{equation*} |
\begin{equation*} |
1495 |
\end{equation*} |
\end{equation*} |
1496 |
|
|
1497 |
\begin{equation*} |
\begin{equation*} |
1498 |
\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 |
1499 |
\lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} |
\lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} |
1500 |
+\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} |
1501 |
\end{equation*} |
\end{equation*} |