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revision 1.2 by cnh, Tue Oct 9 10:48:03 2001 UTC revision 1.28 by jmc, Fri Aug 27 13:13:30 2010 UTC
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1  % $Header$  % $Header$
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3    
4  %%%% \part{MIT GCM basics}  %tci%\documentclass[12pt]{book}
5    %tci%\usepackage{amsmath}
6    %tci%\usepackage{html}
7    %tci%\usepackage{epsfig}
8    %tci%\usepackage{graphics,subfigure}
9    %tci%\usepackage{array}
10    %tci%\usepackage{multirow}
11    %tci%\usepackage{fancyhdr}
12    %tci%\usepackage{psfrag}
13    
14    %tci%%TCIDATA{OutputFilter=Latex.dll}
15    %tci%%TCIDATA{LastRevised=Thursday, October 04, 2001 14:41:22}
16    %tci%%TCIDATA{<META NAME="GraphicsSave" CONTENT="32">}
17    %tci%%TCIDATA{Language=American English}
18    
19    %tci%\fancyhead{}
20    %tci%\fancyhead[LO]{\slshape \rightmark}
21    %tci%\fancyhead[RE]{\slshape \leftmark}
22    %tci%\fancyhead[RO,LE]{\thepage}
23    %tci%\fancyfoot[CO,CE]{\today}
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27    %tci%\setcounter{secnumdepth}{3}
28    %tci%\input{tcilatex}
29    
30    %tci%\begin{document}
31    
32    %tci%\tableofcontents
33    
34    
35  % Section: Overview  % Section: Overview
36    
37  % $Header$  % $Header$
38  % $Name$  % $Name$
39    
40  \section{Introduction}  This document provides the reader with the information necessary to
   
 This documentation provides the reader with the information necessary to  
41  carry out numerical experiments using MITgcm. It gives a comprehensive  carry out numerical experiments using MITgcm. It gives a comprehensive
42  description of the continuous equations on which the model is based, the  description of the continuous equations on which the model is based, the
43  numerical algorithms the model employs and a description of the associated  numerical algorithms the model employs and a description of the associated
# Line 72  are available. A number of examples illu Line 47  are available. A number of examples illu
47  both process and general circulation studies of the atmosphere and ocean are  both process and general circulation studies of the atmosphere and ocean are
48  also presented.  also presented.
49    
50    \section{Introduction}
51    \begin{rawhtml}
52    <!-- CMIREDIR:innovations: -->
53    \end{rawhtml}
54    
55    
56  MITgcm has a number of novel aspects:  MITgcm has a number of novel aspects:
57    
58  \begin{itemize}  \begin{itemize}
59  \item it can be used to study both atmospheric and oceanic phenomena; one  \item it can be used to study both atmospheric and oceanic phenomena; one
60  hydrodynamical kernel is used to drive forward both atmospheric and oceanic  hydrodynamical kernel is used to drive forward both atmospheric and oceanic
61  models - see fig.1%  models - see fig \ref{fig:onemodel}
62  \marginpar{  
63  Fig.1 One model}\ref{fig:onemodel}  %% CNHbegin
64    \input{s_overview/text/one_model_figure}
65    %% 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.2%  small-scale and large scale processes - see fig \ref{fig:all-scales}
69  \marginpar{  
70  Fig.2 All scales}\ref{fig:all-scales}  %% CNHbegin
71    \input{s_overview/text/all_scales_figure}
72    %% CNHend
73    
74  \item finite volume techniques are employed yielding an intuitive  \item finite volume techniques are employed yielding an intuitive
75  discretization and support for the treatment of irregular geometries using  discretization and support for the treatment of irregular geometries using
76  orthogonal curvilinear grids and shaved cells - see fig.3%  orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes}
77  \marginpar{  
78  Fig.3 Finite volumes}\ref{fig:Finite volumes}  %% CNHbegin
79    \input{s_overview/text/fvol_figure}
80    %% CNHend
81    
82  \item tangent linear and adjoint counterparts are automatically maintained  \item tangent linear and adjoint counterparts are automatically maintained
83  along with the forward model, permitting sensitivity and optimization  along with the forward model, permitting sensitivity and optimization
# Line 100  studies. Line 87  studies.
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  listed in an Appendix.  \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}
96    Hill, C. and J. Marshall, (1995)
97    Application of a Parallel Navier-Stokes Model to Ocean Circulation in
98    Parallel Computational Fluid Dynamics
99    In Proceedings of Parallel Computational Fluid Dynamics: Implementations
100    and Results Using Parallel Computers, 545-552.
101    Elsevier Science B.V.: New York
102    
103    Marshall, J., C. Hill, L. Perelman, and A. Adcroft, (1997)
104    Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling
105    J. Geophysical Res., 102(C3), 5733-5752.
106    
107    Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, (1997)
108    A finite-volume, incompressible Navier Stokes model for studies of the ocean
109    on parallel computers,
110    J. Geophysical Res., 102(C3), 5753-5766.
111    
112    Adcroft, A.J., Hill, C.N. and J. Marshall, (1997)
113    Representation of topography by shaved cells in a height coordinate ocean
114    model
115    Mon Wea Rev, vol 125, 2293-2315
116    
117    Marshall, J., Jones, H. and C. Hill, (1998)
118    Efficient ocean modeling using non-hydrostatic algorithms
119    Journal of Marine Systems, 18, 115-134
120    
121    Adcroft, A., Hill C. and J. Marshall: (1999)
122    A new treatment of the Coriolis terms in C-grid models at both high and low
123    resolutions,
124    Mon. Wea. Rev. Vol 127, pages 1928-1936
125    
126    Hill, C, Adcroft,A., Jamous,D., and J. Marshall, (1999)
127    A Strategy for Terascale Climate Modeling.
128    In Proceedings of the Eighth ECMWF Workshop on the Use of Parallel Processors
129    in Meteorology, pages 406-425
130    World Scientific Publishing Co: UK
131    
132    Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999)
133    Construction of the adjoint MIT ocean general circulation model and
134    application to Atlantic heat transport variability
135    J. Geophysical Res., 104(C12), 29,529-29,547.
136    
137    \end{verbatim}
138    
139  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
140  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.
 \pagebreak  
141    
142  % $Header$  % $Header$
143  % $Name$  % $Name$
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 fig.2\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
151  of them here. A more detailed description of the underlying formulation,  of them here. A more detailed description of the underlying formulation,
152  numerical algorithm and implementation that lie behind these calculations is  numerical algorithm and implementation that lie behind these calculations is
153  given later. Indeed many of the illustrative examples shown below can be  given later. Indeed many of the illustrative examples shown below can be
154  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
155  running linux, together with a FORTRAN\ 77 compiler) and follow the examples  running Linux, together with a FORTRAN\ 77 compiler) and follow the examples
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    
163    
 A novel feature of MITgcm is its ability to simulate both atmospheric and  
 oceanographic flows at both small and large scales.  
164    
165  Fig.E1a.\ref{fig:Held-Suarez} shows an instantaneous plot of the 500$mb$  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.
167    
168    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,
# Line 139  radiative-convective equilibrium profile Line 176  radiative-convective equilibrium profile
176  in Held and Suarez; 1994 designed to test atmospheric hydrodynamical cores -  in Held and Suarez; 1994 designed to test atmospheric hydrodynamical cores -
177  there are no mountains or land-sea contrast.  there are no mountains or land-sea contrast.
178    
179    %% CNHbegin
180    \input{s_overview/text/cubic_eddies_figure}
181    %% 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
184  globe permitting a uniform gridding and obviated the need to fourier filter.  globe permitting a uniform griding and obviated the need to Fourier filter.
185  The `vector-invariant' form of MITgcm supports any orthogonal curvilinear  The `vector-invariant' form of MITgcm supports any orthogonal curvilinear
186  grid, of which the cubed sphere is just one of many choices.  grid, of which the cubed sphere is just one of many choices.
187    
188  Fig.E1b shows the 5-year mean, zonally averaged potential temperature, zonal  Figure \ref{fig:hs_zave_u} shows the 5-year mean, zonally averaged zonal
189  wind and meridional overturning streamfunction from a 20-level version of  wind from a 20-level configuration of
190  the model. It compares favorable with more conventional spatial  the model. It compares favorable with more conventional spatial
191  discretization approaches.  discretization approaches. The two plots show the field calculated using the
192    cube-sphere grid and the flow calculated using a regular, spherical polar
193  A regular spherical lat-lon grid can also be used.  latitude-longitude grid. Both grids are supported within the model.
194    
195    %% CNHbegin
196    \input{s_overview/text/hs_zave_u_figure}
197    %% 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
# Line 161  diffusive patterns of ocean currents. Bu Line 212  diffusive patterns of ocean currents. Bu
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  Fig. ?.? shows the surface temperature and velocity field obtained from  Figure \ref{fig:ocean-gyres} shows the surface temperature and
216  MITgcm run at $\frac{1}{6}^{\circ }$ horizontal resolution on a $lat-lon$  velocity field obtained from MITgcm run at $\frac{1}{6}^{\circ }$
217  grid in which the pole has been rotated by 90$^{\circ }$ on to the equator  horizontal resolution on a \textit{lat-lon} grid in which the pole has
218  (to avoid the converging of meridian in northern latitudes). 21 vertical  been rotated by $90^{\circ }$ on to the equator (to avoid the
219  levels are used in the vertical with a `lopped cell' representation of  converging of meridian in northern latitudes). 21 vertical levels are
220  topography. The development and propagation of anomalously warm and cold  used in the vertical with a `lopped cell' representation of
221  eddies can be clearly been seen in the Gulf Stream region. The transport of  topography. The development and propagation of anomalously warm and
222  warm water northward by the mean flow of the Gulf Stream is also clearly  cold eddies can be clearly seen in the Gulf Stream region. The
223  visible.  transport of warm water northward by the mean flow of the Gulf Stream
224    is also clearly visible.
225  \subsection{Global ocean circulation}  
226    %% CNHbegin
227    \input{s_overview/text/atl6_figure}
228    %% CNHend
229    
 Fig.E2a shows the pattern of ocean currents at the surface of a 4$^{\circ }$  
 global ocean model run with 15 vertical levels. Lopped cells are used to  
 represent topography on a regular $lat-lon$ grid extending from 70$^{\circ  
 }N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with  
 mixed boundary conditions on temperature and salinity at the surface. The  
 transfer properties of ocean eddies, convection and mixing is parameterized  
 in this model.  
230    
231  Fig.E2b shows the meridional overturning circulation of the global ocean in  \subsection{Global ocean circulation}
232  Sverdrups.  \begin{rawhtml}
233    <!-- CMIREDIR:global_ocean_circulation: -->
234    \end{rawhtml}
235    
236    Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean
237    currents at the surface of a $4^{\circ }$ global ocean model run with
238    15 vertical levels. Lopped cells are used to represent topography on a
239    regular \textit{lat-lon} grid extending from $70^{\circ }N$ to
240    $70^{\circ }S$. 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
246    circulation of the global ocean in Sverdrups.
247    
248    %%CNHbegin
249    \input{s_overview/text/global_circ_figure}
250    %%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
260  than the width of the cooling region. Rather than gravity plumes, the  than the width of the cooling region. Rather than gravity plumes, the
261  mechanism for moving dense fluid down the shelf is then through geostrophic  mechanism for moving dense fluid down the shelf is then through geostrophic
262  eddies. The simulation shown in the figure (blue is cold dense fluid, red is  eddies. The simulation shown in the figure \ref{fig:convect-and-topo}
263    (blue is cold dense fluid, red is
264  warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to  warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to
265  trigger convection by surface cooling. The cold, dense water falls down the  trigger convection by surface cooling. The cold, dense water falls down the
266  slope but is deflected along the slope by rotation. It is found that  slope but is deflected along the slope by rotation. It is found that
# Line 198  entrainment in the vertical plane is red Line 268  entrainment in the vertical plane is red
268  strong, and replaced by lateral entrainment due to the baroclinic  strong, and replaced by lateral entrainment due to the baroclinic
269  instability of the along-slope current.  instability of the along-slope current.
270    
271    %%CNHbegin
272    \input{s_overview/text/convect_and_topo}
273    %%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
282  dynamics and mixing in oceanic canyons and ridges driven by large amplitude  dynamics and mixing in oceanic canyons and ridges driven by large amplitude
283  barotropic tidal currents imposed through open boundary conditions.  barotropic tidal currents imposed through open boundary conditions.
284    
285  Fig. ?.? shows the influence of cross-slope topographic variations on  Fig. \ref{fig:boundary-forced-wave} shows the influence of cross-slope
286    topographic variations on
287  internal wave breaking - the cross-slope velocity is in color, the density  internal wave breaking - the cross-slope velocity is in color, the density
288  contoured. The internal waves are excited by application of open boundary  contoured. The internal waves are excited by application of open boundary
289  conditions on the left.\ They propagate to the sloping boundary (represented  conditions on the left. They propagate to the sloping boundary (represented
290  using MITgcm's finite volume spatial discretization) where they break under  using MITgcm's finite volume spatial discretization) where they break under
291  nonhydrostatic dynamics.  nonhydrostatic dynamics.
292    
293    %%CNHbegin
294    \input{s_overview/text/boundary_forced_waves}
295    %%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, Fig.E4 maps the  As one example of application of the MITgcm adjoint, Figure
307  gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude  \ref{fig:hf-sensitivity} maps the gradient $\frac{\partial J}{\partial
308  of the overturning streamfunction shown in fig?.? at 40$^{\circ }$N and $%    \mathcal{H}}$where $J$ is the magnitude of the overturning
309  \mathcal{H}$ is the air-sea heat flux 100 years before. We see that $J$ is  stream-function shown in figure \ref{fig:large-scale-circ} at
310  sensitive to heat fluxes over the Labrador Sea, one of the important sources  $60^{\circ }N$ and $ \mathcal{H}(\lambda,\varphi)$ is the mean, local
311  of deep water for the thermohaline circulations. This calculation also  air-sea heat flux over a 100 year period. We see that $J$ is sensitive
312    to heat fluxes over the Labrador Sea, one of the important sources of
313    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
317    \input{s_overview/text/adj_hf_ocean_figure}
318    %%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
328  the departure of the model from observations (both remotely sensed and  the departure of the model from observations (both remotely sensed and
329  insitu) over an interval of time, is minimized by adjusting `control  in-situ) over an interval of time, is minimized by adjusting `control
330  parameters' such as air-sea fluxes, the wind field, the initial conditions  parameters' such as air-sea fluxes, the wind field, the initial conditions
331  etc. Figure ?.? shows an estimate of the time-mean surface elevation of the  etc. Figure \ref{fig:assimilated-globes} shows the large scale planetary
332  ocean obtained by bringing the model in to consistency with altimetric and  circulation and a Hopf-Muller plot of Equatorial sea-surface height.
333  in-situ observations over the period 1992-1997.  Both are obtained from assimilation bringing the model in to
334    consistency with altimetric and in-situ observations over the period
335    1992-1997.
336    
337    %% CNHbegin
338    \input{s_overview/text/assim_figure}
339    %% 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. The figure shows the annual air-sea  MITgcm is being used to study global biogeochemical cycles in the
347  flux of oxygen and its relation to density outcrops in the southern oceans  ocean. For example one can study the effects of interannual changes in
348  from a single year of a global, interannually varying simulation.  meteorological forcing and upper ocean circulation on the fluxes of
349    carbon dioxide and oxygen between the ocean and atmosphere. Figure
350  Chris - get figure here: http://puddle.mit.edu/\symbol{126}%  \ref{fig:biogeo} shows the annual air-sea flux of oxygen and its
351  mick/biogeochem.html  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
358    \input{s_overview/text/biogeo_figure}
359    %%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 ?.? shows MITgcm being used to simulate a laboratory experiment  Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a
367  enquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An  laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An
368  initially homogeneous tank of water ($1m$ in diameter) is driven from its  initially homogeneous tank of water ($1m$ in diameter) is driven from its
369  free surface by a rotating heated disk. The combined action of mechanical  free surface by a rotating heated disk. The combined action of mechanical
370  and thermal forcing creates a lens of fluid which becomes baroclinically  and thermal forcing creates a lens of fluid which becomes baroclinically
371  unstable. The stratification and depth of penetration of the lens is  unstable. The stratification and depth of penetration of the lens is
372  arrested by its instability in a process analogous to that whic sets the  arrested by its instability in a process analogous to that which sets the
373  stratification of the ACC.  stratification of the ACC.
374    
375    %%CNHbegin
376    \input{s_overview/text/lab_figure}
377    %%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
389  respective fluids - see fig.4%  respective fluids - see figure \ref{fig:isomorphic-equations}.
390  \marginpar{  One system of hydrodynamical equations is written down
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down  
391  and encoded. The model variables have different interpretations depending on  and encoded. The model variables have different interpretations depending on
392  whether the atmosphere or ocean is being studied. Thus, for example, the  whether the atmosphere or ocean is being studied. Thus, for example, the
393  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are
394  modeling the atmosphere and height, $z$, if we are modeling the ocean.  modeling the atmosphere (right hand side of figure \ref{fig:isomorphic-equations})
395    and height, $z$, if we are modeling the ocean (left hand side of figure
396    \ref{fig:isomorphic-equations}).
397    
398    %%CNHbegin
399    \input{s_overview/text/zandpcoord_figure.tex}
400    %%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
403  velocity $\vec{\mathbf{v}}$, active tracers $\theta $ and $S$, a  velocity $\vec{\mathbf{v}}$, active tracers $\theta $ and $S$, a
# Line 281  velocity $\vec{\mathbf{v}}$, active trac Line 405  velocity $\vec{\mathbf{v}}$, active trac
405  depend on $\theta $, $S$, and $p$. The equations that govern the evolution  depend on $\theta $, $S$, and $p$. The equations that govern the evolution
406  of these fields, obtained by applying the laws of classical mechanics and  of these fields, obtained by applying the laws of classical mechanics and
407  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of
408  a generic vertical coordinate, $r$, see fig.5%  a generic vertical coordinate, $r$, so that the appropriate
409  \marginpar{  kinematic boundary conditions can be applied isomorphically
410  Fig.5 The vertical coordinate of model}:  see figure \ref{fig:zandp-vert-coord}.
411    
412  \begin{equation*}  %%CNHbegin
413  \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}%  \input{s_overview/text/vertcoord_figure.tex}
414  \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}%  %%CNHend
 \text{ horizontal mtm}  
 \end{equation*}  
415    
416  \begin{equation*}  \begin{equation}
417  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{%  \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}}}
419    \text{ horizontal mtm} \label{eq:horizontal_mtm}
420    \end{equation}
421    
422    \begin{equation}
423    \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{
424  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{
425  vertical mtm}  vertical mtm} \label{eq:vertical_mtm}
426  \end{equation*}  \end{equation}
427    
428  \begin{equation}  \begin{equation}
429  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{%  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{
430  \partial r}=0\text{ continuity}  \label{eq:continuous}  \partial r}=0\text{ continuity}  \label{eq:continuity}
431  \end{equation}  \end{equation}
432    
433  \begin{equation*}  \begin{equation}
434  b=b(\theta ,S,r)\text{ equation of state}  b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state}
435  \end{equation*}  \end{equation}
436    
437  \begin{equation*}  \begin{equation}
438  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}
439  \end{equation*}  \label{eq:potential_temperature}
440    \end{equation}
441    
442  \begin{equation*}  \begin{equation}
443  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}
444  \end{equation*}  \label{eq:humidity_salt}
445    \end{equation}
446    
447  Here:  Here:
448    
# Line 326  is the total derivative} Line 456  is the total derivative}
456  \end{equation*}  \end{equation*}
457    
458  \begin{equation*}  \begin{equation*}
459  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}%  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}
460  \text{ is the `grad' operator}  \text{ is the `grad' operator}
461  \end{equation*}  \end{equation*}
462  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}%  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}
463  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$
464  is a unit vector in the vertical  is a unit vector in the vertical
465    
# Line 363  S\text{ is specific humidity in the atmo Line 493  S\text{ is specific humidity in the atmo
493  \end{equation*}  \end{equation*}
494    
495  \begin{equation*}  \begin{equation*}
496  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{%  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{
497  \mathbf{v}}  \mathbf{v}}
498  \end{equation*}  \end{equation*}
499    
# Line 376  S\text{ is specific humidity in the atmo Line 506  S\text{ is specific humidity in the atmo
506  \end{equation*}  \end{equation*}
507    
508  The $\mathcal{F}^{\prime }s$ and $\mathcal{Q}^{\prime }s$ are provided by  The $\mathcal{F}^{\prime }s$ and $\mathcal{Q}^{\prime }s$ are provided by
509  extensive `physics' packages for atmosphere and ocean described in Chapter 6.  `physics' and forcing packages for atmosphere and ocean. These are described
510    in later chapters.
511    
512  \subsection{Kinematic Boundary conditions}  \subsection{Kinematic Boundary conditions}
513    
514  \subsubsection{vertical}  \subsubsection{vertical}
515    
516  at fixed and moving $r$ surfaces we set (see fig.5):  at fixed and moving $r$ surfaces we set (see figure \ref{fig:zandp-vert-coord}):
517    
518  \begin{equation}  \begin{equation}
519  \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)}
520  \label{eq:fixedbc}  \label{eq:fixedbc}
521  \end{equation}  \end{equation}
522    
523  \begin{equation}  \begin{equation}
524  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \  \dot{r}=\frac{Dr}{Dt} \text{\ at\ } r=R_{moving}\text{ \
525  (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc}  (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc}
526  \end{equation}  \end{equation}
527    
528  Here  Here
# Line 408  of motion. Line 539  of motion.
539    
540  \begin{equation}  \begin{equation}
541  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}
542  \end{equation}%  \end{equation}
543  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.
544    
545  \subsection{Atmosphere}  \subsection{Atmosphere}
546    
547  In the atmosphere, see fig.5, we interpret:  In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret:
548    
549  \begin{equation}  \begin{equation}
550  r=p\text{ is the pressure}  \label{eq:atmos-r}  r=p\text{ is the pressure}  \label{eq:atmos-r}
# Line 445  where Line 576  where
576    
577  \begin{equation*}  \begin{equation*}
578  T\text{ is absolute temperature}  T\text{ is absolute temperature}
579  \end{equation*}%  \end{equation*}
580  \begin{equation*}  \begin{equation*}
581  p\text{ is the pressure}  p\text{ is the pressure}
582  \end{equation*}%  \end{equation*}
583  \begin{eqnarray*}  \begin{eqnarray*}
584  &&z\text{ is the height of the pressure surface} \\  &&z\text{ is the height of the pressure surface} \\
585  &&g\text{ is the acceleration due to gravity}  &&g\text{ is the acceleration due to gravity}
# Line 458  In the above the ideal gas law, $p=\rho Line 589  In the above the ideal gas law, $p=\rho
589  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)
590  \begin{equation}  \begin{equation}
591  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}
592  \end{equation}%  \end{equation}
593  where $p_{c}$ is a reference pressure and $\kappa =R/c_{p}$ with $R$ the gas  where $p_{c}$ is a reference pressure and $\kappa =R/c_{p}$ with $R$ the gas
594  constant and $c_{p}$ the specific heat of air at constant pressure.  constant and $c_{p}$ the specific heat of air at constant pressure.
595    
# Line 484  The boundary conditions at top and botto Line 615  The boundary conditions at top and botto
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) eq(\ref{eq:continuous}) yields a consistent  Then the (hydrostatic form of) equations
619  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    
# Line 508  At the bottom of the ocean: $R_{fixed}(x Line 641  At the bottom of the ocean: $R_{fixed}(x
641    
642  The surface of the ocean is given by: $R_{moving}=\eta $  The surface of the ocean is given by: $R_{moving}=\eta $
643    
644  The position of the resting free surface of the ocean is given by $%  The position of the resting free surface of the ocean is given by $
645  R_{o}=Z_{o}=0$.  R_{o}=Z_{o}=0$.
646    
647  Boundary conditions are:  Boundary conditions are:
# Line 516  Boundary conditions are: Line 649  Boundary conditions are:
649  \begin{eqnarray}  \begin{eqnarray}
650  w &=&0~\text{at }r=R_{fixed}\text{ (ocean bottom)}  \label{eq:fixed-bc-ocean}  w &=&0~\text{at }r=R_{fixed}\text{ (ocean bottom)}  \label{eq:fixed-bc-ocean}
651  \\  \\
652  w &=&\frac{D\eta }{Dt}\text{ at }r=R_{moving}=\eta \text{ (ocean surface) %  w &=&\frac{D\eta }{Dt}\text{ at }r=R_{moving}=\eta \text{ (ocean surface)
653  \label{eq:moving-bc-ocean}}  \label{eq:moving-bc-ocean}}
654  \end{eqnarray}  \end{eqnarray}
655  where $\eta $ is the elevation of the free surface.  where $\eta $ is the elevation of the free surface.
656    
657  Then eq(\ref{eq:continuous}) yields a consistent set of oceanic equations  Then equations (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt}) yield a consistent set
658    of oceanic equations
659  which, for convenience, are written out in $z$ coordinates in Appendix Ocean  which, for convenience, are written out in $z$ coordinates in Appendix Ocean
660  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).
661    
662  \subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and  \subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and
663  Non-hydrostatic forms}  Non-hydrostatic forms}
664    \begin{rawhtml}
665    <!-- CMIREDIR:non_hydrostatic: -->
666    \end{rawhtml}
667    
668    
669  Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms:  Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms:
670    
671  \begin{equation}  \begin{equation}
672  \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)
673  \label{eq:phi-split}  \label{eq:phi-split}
674  \end{equation}%  \end{equation}
675  and write eq(\ref{incompressible}a,b) in the form:  %and write eq(\ref{eq:incompressible}) in the form:
676    %                  ^- this eq is missing (jmc) ; replaced with:
677    and write eq( \ref{eq:horizontal_mtm}) in the form:
678    
679  \begin{equation}  \begin{equation}
680  \frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi  \frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi
# Line 547  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l Line 687  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l
687  \end{equation}  \end{equation}
688    
689  \begin{equation}  \begin{equation}
690  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{%  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{
691  \partial r}=G_{\dot{r}}  \label{eq:mom-w}  \partial r}=G_{\dot{r}}  \label{eq:mom-w}
692  \end{equation}  \end{equation}
693  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.
694    
695  The $\left( \vec{\mathbf{G}}_{\vec{v}},G_{\dot{r}}\right) $ in eq(\ref%  The $\left( \vec{\mathbf{G}}_{\vec{v}},G_{\dot{r}}\right) $ in eq(\ref
696  {eq:mom-h}) and (\ref{eq:mom-w}) represent advective, metric and Coriolis  {eq:mom-h}) and (\ref{eq:mom-w}) represent advective, metric and Coriolis
697  terms in the momentum equations. In spherical coordinates they take the form%  terms in the momentum equations. In spherical coordinates they take the form
698  \footnote{%  \footnote{
699  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms
700  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref%  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref
701  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in
702  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (%  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (
703  \textbf{NH}) includes all terms.} - see Marshall et al 1997a for a full  \textbf{NH}) includes all terms.} - see Marshall et al 1997a for a full
704  discussion:  discussion:
705    
# Line 567  discussion: Line 707  discussion:
707  \left.  \left.
708  \begin{tabular}{l}  \begin{tabular}{l}
709  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\
710  $-\left\{ \underline{\frac{u\dot{r}}{{r}}}-\frac{uv\tan lat}{{r}}\right\} $  $-\left\{ \underline{\frac{u\dot{r}}{{r}}}-\frac{uv\tan \varphi}{{r}}\right\} $
711  \\  \\
712  $-\left\{ -2\Omega v\sin lat+\underline{2\Omega \dot{r}\cos lat}\right\} $  $-\left\{ -2\Omega v\sin \varphi+\underline{2\Omega \dot{r}\cos \varphi}\right\} $
713  \\  \\
714  $+\mathcal{F}_{u}$%  $+\mathcal{F}_{u}$
715  \end{tabular}%  \end{tabular}
716  \ \right\} \left\{  \ \right\} \left\{
717  \begin{tabular}{l}  \begin{tabular}{l}
718  \textit{advection} \\  \textit{advection} \\
719  \textit{metric} \\  \textit{metric} \\
720  \textit{Coriolis} \\  \textit{Coriolis} \\
721  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
722  \end{tabular}%  \end{tabular}
723  \ \right. \qquad  \label{eq:gu-speherical}  \ \right. \qquad  \label{eq:gu-speherical}
724  \end{equation}  \end{equation}
725    
# Line 587  $+\mathcal{F}_{u}$% Line 727  $+\mathcal{F}_{u}$%
727  \left.  \left.
728  \begin{tabular}{l}  \begin{tabular}{l}
729  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\
730  $-\left\{ \underline{\frac{v\dot{r}}{{r}}}-\frac{u^{2}\tan lat}{{r}}\right\}  $-\left\{ \underline{\frac{v\dot{r}}{{r}}}-\frac{u^{2}\tan \varphi}{{r}}\right\}
731  $ \\  $ \\
732  $-\left\{ -2\Omega u\sin lat\right\} $ \\  $-\left\{ -2\Omega u\sin \varphi \right\} $ \\
733  $+\mathcal{F}_{v}$%  $+\mathcal{F}_{v}$
734  \end{tabular}%  \end{tabular}
735  \ \right\} \left\{  \ \right\} \left\{
736  \begin{tabular}{l}  \begin{tabular}{l}
737  \textit{advection} \\  \textit{advection} \\
738  \textit{metric} \\  \textit{metric} \\
739  \textit{Coriolis} \\  \textit{Coriolis} \\
740  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
741  \end{tabular}%  \end{tabular}
742  \ \right. \qquad  \label{eq:gv-spherical}  \ \right. \qquad  \label{eq:gv-spherical}
743  \end{equation}%  \end{equation}
744  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
745    
746  \begin{equation}  \begin{equation}
# Line 608  $+\mathcal{F}_{v}$% Line 748  $+\mathcal{F}_{v}$%
748  \begin{tabular}{l}  \begin{tabular}{l}
749  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\
750  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\
751  ${+}\underline{{2\Omega u\cos lat}}$ \\  ${+}\underline{{2\Omega u\cos \varphi}}$ \\
752  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$%  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$
753  \end{tabular}%  \end{tabular}
754  \ \right\} \left\{  \ \right\} \left\{
755  \begin{tabular}{l}  \begin{tabular}{l}
756  \textit{advection} \\  \textit{advection} \\
757  \textit{metric} \\  \textit{metric} \\
758  \textit{Coriolis} \\  \textit{Coriolis} \\
759  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
760  \end{tabular}%  \end{tabular}
761  \ \right.  \label{eq:gw-spherical}  \ \right.  \label{eq:gw-spherical}
762  \end{equation}%  \end{equation}
763  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
764    
765  In the above `${r}$' is the distance from the center of the earth and `$lat$%  In the above `${r}$' is the distance from the center of the earth and `$\varphi$
766  ' is latitude.  ' is latitude.
767    
768  Grad and div operators in spherical coordinates are defined in appendix  Grad and div operators in spherical coordinates are defined in appendix
769  OPERATORS.%  OPERATORS.
770  \marginpar{  
771  Fig.6 Spherical polar coordinate system.}  %%CNHbegin
772    \input{s_overview/text/sphere_coord_figure.tex}
773    %%CNHend
774    
775  \subsubsection{Shallow atmosphere approximation}  \subsubsection{Shallow atmosphere approximation}
776    
777  Most models are based on the `hydrostatic primitive equations' (HPE's) in  Most models are based on the `hydrostatic primitive equations' (HPE's)
778  which the vertical momentum equation is reduced to a statement of  in which the vertical momentum equation is reduced to a statement of
779  hydrostatic balance and the `traditional approximation' is made in which the  hydrostatic balance and the `traditional approximation' is made in
780  Coriolis force is treated approximately and the shallow atmosphere  which the Coriolis force is treated approximately and the shallow
781  approximation is made.\ The MITgcm need not make the `traditional  atmosphere approximation is made.  MITgcm need not make the
782  approximation'. To be able to support consistent non-hydrostatic forms the  `traditional approximation'. To be able to support consistent
783  shallow atmosphere approximation can be relaxed - when dividing through by $%  non-hydrostatic forms the shallow atmosphere approximation can be
784  r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$,  relaxed - when dividing through by $ r $ in, for example,
785  the radius of the earth.  (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, the radius of
786    the earth.
787    
788  \subsubsection{Hydrostatic and quasi-hydrostatic forms}  \subsubsection{Hydrostatic and quasi-hydrostatic forms}
789    \label{sec:hydrostatic_and_quasi-hydrostatic_forms}
790    
791  These are discussed at length in Marshall et al (1997a).  These are discussed at length in Marshall et al (1997a).
792    
# Line 651  terms in Eqs. (\ref{eq:gu-speherical} $\ Line 795  terms in Eqs. (\ref{eq:gu-speherical} $\
795  are neglected and `${r}$' is replaced by `$a$', the mean radius of the  are neglected and `${r}$' is replaced by `$a$', the mean radius of the
796  earth. Once the pressure is found at one level - e.g. by inverting a 2-d  earth. Once the pressure is found at one level - e.g. by inverting a 2-d
797  Elliptic equation for $\phi _{s}$ at $r=R_{moving}$ - the pressure can be  Elliptic equation for $\phi _{s}$ at $r=R_{moving}$ - the pressure can be
798  computed at all other levels by integration of the hydrostatic relation, eq(%  computed at all other levels by integration of the hydrostatic relation, eq(
799  \ref{eq:hydrostatic}).  \ref{eq:hydrostatic}).
800    
801  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between
802  gravity and vertical pressure gradients is not imposed. The $2\Omega u\cos  gravity and vertical pressure gradients is not imposed. The $2\Omega u\cos
803  \phi $ Coriolis term are not neglected and are balanced by a non-hydrostatic  \varphi $ Coriolis term are not neglected and are balanced by a non-hydrostatic
804  contribution to the pressure field: only the terms underlined twice in Eqs. (%  contribution to the pressure field: only the terms underlined twice in Eqs. (
805  \ref{eq:gu-speherical}$\rightarrow $\ \ref{eq:gw-spherical}) are set to zero  \ref{eq:gu-speherical}$\rightarrow $\ \ref{eq:gw-spherical}) are set to zero
806  and, simultaneously, the shallow atmosphere approximation is relaxed. In  and, simultaneously, the shallow atmosphere approximation is relaxed. In
807  \textbf{QH}\ \textit{all} the metric terms are retained and the full  \textbf{QH}\ \textit{all} the metric terms are retained and the full
# Line 665  variation of the radial position of a pa Line 809  variation of the radial position of a pa
809  vertical momentum equation (\ref{eq:mom-w}) becomes:  vertical momentum equation (\ref{eq:mom-w}) becomes:
810    
811  \begin{equation*}  \begin{equation*}
812  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos lat  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos \varphi
813  \end{equation*}  \end{equation*}
814  making a small correction to the hydrostatic pressure.  making a small correction to the hydrostatic pressure.
815    
# Line 676  et.al., 1997a. As in \textbf{HPE }only a Line 820  et.al., 1997a. As in \textbf{HPE }only a
820    
821  \subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms}  \subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms}
822    
823  The MIT model presently supports a full non-hydrostatic ocean isomorph, but  MITgcm presently supports a full non-hydrostatic ocean isomorph, but
824  only a quasi-non-hydrostatic atmospheric isomorph.  only a quasi-non-hydrostatic atmospheric isomorph.
825    
826  \paragraph{Non-hydrostatic Ocean}  \paragraph{Non-hydrostatic Ocean}
827    
828  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref%  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref
829  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A
830  three dimensional elliptic equation must be solved subject to Neumann  three dimensional elliptic equation must be solved subject to Neumann
831  boundary conditions (see below). It is important to note that use of the  boundary conditions (see below). It is important to note that use of the
832  full \textbf{NH} does not admit any new `fast' waves in to the system - the  full \textbf{NH} does not admit any new `fast' waves in to the system - the
833  incompressible condition eq(\ref{eq:continuous})c has already filtered out  incompressible condition eq(\ref{eq:continuity}) has already filtered out
834  acoustic modes. It does, however, ensure that the gravity waves are treated  acoustic modes. It does, however, ensure that the gravity waves are treated
835  accurately with an exact dispersion relation. The \textbf{NH} set has a  accurately with an exact dispersion relation. The \textbf{NH} set has a
836  complete angular momentum principle and consistent energetics - see White  complete angular momentum principle and consistent energetics - see White
# Line 694  and Bromley, 1995; Marshall et.al.\ 1997 Line 838  and Bromley, 1995; Marshall et.al.\ 1997
838    
839  \paragraph{Quasi-nonhydrostatic Atmosphere}  \paragraph{Quasi-nonhydrostatic Atmosphere}
840    
841  In the non-hydrostatic version of our atmospheric model we approximate $\dot{%  In the non-hydrostatic version of our atmospheric model we approximate $\dot{
842  r}$ in the vertical momentum eqs(\ref{eq:mom-w}) and (\ref{eq:gv-spherical})  r}$ in the vertical momentum eqs(\ref{eq:mom-w}) and (\ref{eq:gv-spherical})
843  (but only here) by:  (but only here) by:
844    
845  \begin{equation}  \begin{equation}
846  \dot{r}=\frac{Dp}{Dt}=\frac{1}{g}\frac{D\phi }{Dt}  \label{eq:quasi-nh-w}  \dot{r}=\frac{Dp}{Dt}=\frac{1}{g}\frac{D\phi }{Dt}  \label{eq:quasi-nh-w}
847  \end{equation}%  \end{equation}
848  where $p_{hy}$ is the hydrostatic pressure.  where $p_{hy}$ is the hydrostatic pressure.
849    
850  \subsubsection{Summary of equation sets supported by model}  \subsubsection{Summary of equation sets supported by model}
# Line 728  equations in $z-$coordinates are support Line 872  equations in $z-$coordinates are support
872    
873  \subparagraph{Non-hydrostatic}  \subparagraph{Non-hydrostatic}
874    
875  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$%  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$
876  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref%  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref
877  {eq:ocean-salt}).  {eq:ocean-salt}).
878    
879  \subsection{Solution strategy}  \subsection{Solution strategy}
880    
881  The method of solution employed in the \textbf{HPE}, \textbf{QH} and \textbf{%  The method of solution employed in the \textbf{HPE}, \textbf{QH} and \textbf{
882  NH} models is summarized in Fig.7.%  NH} models is summarized in Figure \ref{fig:solution-strategy}.
883  \marginpar{  Under all dynamics, a 2-d elliptic equation is
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is  
884  first solved to find the surface pressure and the hydrostatic pressure at  first solved to find the surface pressure and the hydrostatic pressure at
885  any level computed from the weight of fluid above. Under \textbf{HPE} and  any level computed from the weight of fluid above. Under \textbf{HPE} and
886  \textbf{QH} dynamics, the horizontal momentum equations are then stepped  \textbf{QH} dynamics, the horizontal momentum equations are then stepped
# Line 746  forward and $\dot{r}$ found from continu Line 889  forward and $\dot{r}$ found from continu
889  stepping forward the horizontal momentum equations; $\dot{r}$ is found by  stepping forward the horizontal momentum equations; $\dot{r}$ is found by
890  stepping forward the vertical momentum equation.  stepping forward the vertical momentum equation.
891    
892    %%CNHbegin
893    \input{s_overview/text/solution_strategy_figure.tex}
894    %%CNHend
895    
896  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
897  course, some complication that goes with the inclusion of $\cos \phi \ $%  course, some complication that goes with the inclusion of $\cos \varphi \ $
898  Coriolis terms and the relaxation of the shallow atmosphere approximation.  Coriolis terms and the relaxation of the shallow atmosphere approximation.
899  But this leads to negligible increase in computation. In \textbf{NH}, in  But this leads to negligible increase in computation. In \textbf{NH}, in
900  contrast, one additional elliptic equation - a three-dimensional one - must  contrast, one additional elliptic equation - a three-dimensional one - must
# Line 757  Marshall et al, 1997) resulting in a non Line 904  Marshall et al, 1997) resulting in a non
904  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.
905    
906  \subsection{Finding the pressure field}  \subsection{Finding the pressure field}
907    \label{sec:finding_the_pressure_field}
908    
909  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the
910  pressure field must be obtained diagnostically. We proceed, as before, by  pressure field must be obtained diagnostically. We proceed, as before, by
# Line 771  Hydrostatic pressure is obtained by inte Line 919  Hydrostatic pressure is obtained by inte
919  vertically from $r=R_{o}$ where $\phi _{hyd}(r=R_{o})=0$, to yield:  vertically from $r=R_{o}$ where $\phi _{hyd}(r=R_{o})=0$, to yield:
920    
921  \begin{equation*}  \begin{equation*}
922  \int_{r}^{R_{o}}\frac{\partial \phi _{hyd}}{\partial r}dr=\left[ \phi _{hyd}%  \int_{r}^{R_{o}}\frac{\partial \phi _{hyd}}{\partial r}dr=\left[ \phi _{hyd}
923  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr
924  \end{equation*}  \end{equation*}
925  and so  and so
# Line 789  atmospheric pressure pushing down on the Line 937  atmospheric pressure pushing down on the
937    
938  \subsubsection{Surface pressure}  \subsubsection{Surface pressure}
939    
940  The surface pressure equation can be obtained by integrating continuity, (%  The surface pressure equation can be obtained by integrating continuity,
941  \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$  (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$
942    
943  \begin{equation*}  \begin{equation*}
944  \int_{R_{fixed}}^{R_{moving}}\left( \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}%  \int_{R_{fixed}}^{R_{moving}}\left( \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}
945  }_{h}+\partial _{r}\dot{r}\right) dr=0  }_{h}+\partial _{r}\dot{r}\right) dr=0
946  \end{equation*}  \end{equation*}
947    
# Line 801  Thus: Line 949  Thus:
949    
950  \begin{equation*}  \begin{equation*}
951  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta
952  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}%  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}
953  _{h}dr=0  _{h}dr=0
954  \end{equation*}  \end{equation*}
955  where $\eta =R_{moving}-R_{o}$ is the free-surface $r$-anomaly in units of $%  where $\eta =R_{moving}-R_{o}$ is the free-surface $r$-anomaly in units of $
956  r $. The above can be rearranged to yield, using Leibnitz's theorem:  r $. The above can be rearranged to yield, using Leibnitz's theorem:
957    
958  \begin{equation}  \begin{equation}
959  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot
960  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}
961  \label{eq:free-surface}  \label{eq:free-surface}
962  \end{equation}%  \end{equation}
963  where we have incorporated a source term.  where we have incorporated a source term.
964    
965  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential
966  (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can  (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can
967  be written  be written
968  \begin{equation}  \begin{equation}
969  \mathbf{\nabla }_{h}\phi _{s}=\mathbf{\nabla }_{h}\left( b_{s}\eta \right)  \mathbf{\nabla }_{h}\phi _{s}=\mathbf{\nabla }_{h}\left( b_{s}\eta \right)
970  \label{eq:phi-surf}  \label{eq:phi-surf}
971  \end{equation}%  \end{equation}
972  where $b_{s}$ is the buoyancy at the surface.  where $b_{s}$ is the buoyancy at the surface.
973    
974  In the hydrostatic limit ($\epsilon _{nh}=0$), Eqs(\ref{eq:mom-h}), (\ref%  In the hydrostatic limit ($\epsilon _{nh}=0$), equations (\ref{eq:mom-h}), (\ref
975  {eq:free-surface}) and (\ref{eq:phi-surf}) can be solved by inverting a 2-d  {eq:free-surface}) and (\ref{eq:phi-surf}) can be solved by inverting a 2-d
976  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free
977  surface' and `rigid lid' approaches are available.  surface' and `rigid lid' approaches are available.
978    
979  \subsubsection{Non-hydrostatic pressure}  \subsubsection{Non-hydrostatic pressure}
980    
981  Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{%  Taking the horizontal divergence of (\ref{eq:mom-h}) and adding
982  \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation  $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation
983  (\ref{incompressible}), we deduce that:  (\ref{eq:continuity}), we deduce that:
984    
985  \begin{equation}  \begin{equation}
986  \nabla _{3}^{2}\phi _{nh}=\nabla .\vec{\mathbf{G}}_{\vec{v}}-\left( \mathbf{%  \nabla _{3}^{2}\phi _{nh}=\nabla .\vec{\mathbf{G}}_{\vec{v}}-\left( \mathbf{
987  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .%  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .
988  \vec{\mathbf{F}}  \label{eq:3d-invert}  \vec{\mathbf{F}}  \label{eq:3d-invert}
989  \end{equation}  \end{equation}
990    
# Line 856  coasts (in the ocean) and the bottom: Line 1004  coasts (in the ocean) and the bottom:
1004  \end{equation}  \end{equation}
1005  where $\widehat{n}$ is a vector of unit length normal to the boundary. The  where $\widehat{n}$ is a vector of unit length normal to the boundary. The
1006  kinematic condition (\ref{nonormalflow}) is also applied to the vertical  kinematic condition (\ref{nonormalflow}) is also applied to the vertical
1007  velocity at $r=R_{moving}$. No-slip $\left( v_{T}=0\right) \ $or slip $%  velocity at $r=R_{moving}$. No-slip $\left( v_{T}=0\right) \ $or slip $
1008  \left( \partial v_{T}/\partial n=0\right) \ $conditions are employed on the  \left( \partial v_{T}/\partial n=0\right) \ $conditions are employed on the
1009  tangential component of velocity, $v_{T}$, at all solid boundaries,  tangential component of velocity, $v_{T}$, at all solid boundaries,
1010  depending on the form chosen for the dissipative terms in the momentum  depending on the form chosen for the dissipative terms in the momentum
1011  equations - see below.  equations - see below.
1012    
1013  Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that:  Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that:
1014    
1015  \begin{equation}  \begin{equation}
1016  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}
# Line 873  where Line 1021  where
1021  \begin{equation*}  \begin{equation*}
1022  \vec{\mathbf{F}}=\vec{\mathbf{G}}_{\vec{v}}-\left( \mathbf{\nabla }_{h}\phi  \vec{\mathbf{F}}=\vec{\mathbf{G}}_{\vec{v}}-\left( \mathbf{\nabla }_{h}\phi
1023  _{s}+\mathbf{\nabla }\phi _{hyd}\right)  _{s}+\mathbf{\nabla }\phi _{hyd}\right)
1024  \end{equation*}%  \end{equation*}
1025  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem
1026  (\ref{eq:3d-invert}). As shown, for example, by Williams (1969), one can  (\ref{eq:3d-invert}). As shown, for example, by Williams (1969), one can
1027  exploit classical 3D potential theory and, by introducing an appropriately  exploit classical 3D potential theory and, by introducing an appropriately
1028  chosen $\delta $-function sheet of `source-charge', replace the  chosen $\delta $-function sheet of `source-charge', replace the
1029  inhomogeneous boundary condition on pressure by a homogeneous one. The  inhomogeneous boundary condition on pressure by a homogeneous one. The
1030  source term $rhs$ in (\ref{eq:3d-invert}) is the divergence of the vector $%  source term $rhs$ in (\ref{eq:3d-invert}) is the divergence of the vector $
1031  \vec{\mathbf{F}}.$ By simultaneously setting $%  \vec{\mathbf{F}}.$ By simultaneously setting $
1032  \begin{array}{l}  \begin{array}{l}
1033  \widehat{n}.\vec{\mathbf{F}}%  \widehat{n}.\vec{\mathbf{F}}
1034  \end{array}%  \end{array}
1035  =0$\ and $\widehat{n}.\nabla \phi _{nh}=0\ $on the boundary the following  =0$\ and $\widehat{n}.\nabla \phi _{nh}=0\ $on the boundary the following
1036  self-consistent but simpler homogenized Elliptic problem is obtained:  self-consistent but simpler homogenized Elliptic problem is obtained:
1037    
1038  \begin{equation*}  \begin{equation*}
1039  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad
1040  \end{equation*}%  \end{equation*}
1041  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such
1042  that $\widetilde{\vec{\mathbf{F}}}.\widehat{n}=0$. As is implied by (\ref%  that $\widetilde{\vec{\mathbf{F}}}.\widehat{n}=0$. As is implied by (\ref
1043  {eq:inhom-neumann-nh}) the modified boundary condition becomes:  {eq:inhom-neumann-nh}) the modified boundary condition becomes:
1044    
1045  \begin{equation}  \begin{equation}
# Line 902  If the flow is `close' to hydrostatic ba Line 1050  If the flow is `close' to hydrostatic ba
1050  converges rapidly because $\phi _{nh}\ $is then only a small correction to  converges rapidly because $\phi _{nh}\ $is then only a small correction to
1051  the hydrostatic pressure field (see the discussion in Marshall et al, a,b).  the hydrostatic pressure field (see the discussion in Marshall et al, a,b).
1052    
1053  The solution $\phi _{nh}\ $to (\ref{eq:3d-invert}) and (\ref{homneuman})  The solution $\phi _{nh}\ $to (\ref{eq:3d-invert}) and (\ref{eq:inhom-neumann-nh})
1054  does not vanish at $r=R_{moving}$, and so refines the pressure there.  does not vanish at $r=R_{moving}$, and so refines the pressure there.
1055    
1056  \subsection{Forcing/dissipation}  \subsection{Forcing/dissipation}
# Line 910  does not vanish at $r=R_{moving}$, and s Line 1058  does not vanish at $r=R_{moving}$, and s
1058  \subsubsection{Forcing}  \subsubsection{Forcing}
1059    
1060  The forcing terms $\mathcal{F}$ on the rhs of the equations are provided by  The forcing terms $\mathcal{F}$ on the rhs of the equations are provided by
1061  `physics packages' described in detail in chapter ??.  `physics packages' and forcing packages. These are described later on.
1062    
1063  \subsubsection{Dissipation}  \subsubsection{Dissipation}
1064    
# Line 920  Many forms of momentum dissipation are a Line 1068  Many forms of momentum dissipation are a
1068  biharmonic frictions are commonly used:  biharmonic frictions are commonly used:
1069    
1070  \begin{equation}  \begin{equation}
1071  D_{V}=A_{h}\nabla _{h}^{2}v+A_{v}\frac{\partial ^{2}v}{\partial z^{2}}%  D_{V}=A_{h}\nabla _{h}^{2}v+A_{v}\frac{\partial ^{2}v}{\partial z^{2}}
1072  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}
1073  \end{equation}  \end{equation}
1074  where $A_{h}$ and $A_{v}\ $are (constant) horizontal and vertical viscosity  where $A_{h}$ and $A_{v}\ $are (constant) horizontal and vertical viscosity
# Line 931  friction. These coefficients are the sam Line 1079  friction. These coefficients are the sam
1079    
1080  The mixing terms for the temperature and salinity equations have a similar  The mixing terms for the temperature and salinity equations have a similar
1081  form to that of momentum except that the diffusion tensor can be  form to that of momentum except that the diffusion tensor can be
1082  non-diagonal and have varying coefficients. $\qquad $%  non-diagonal and have varying coefficients.
1083  \begin{equation}  \begin{equation}
1084  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
1085  _{h}^{4}(T,S)  \label{eq:diffusion}  _{h}^{4}(T,S)  \label{eq:diffusion}
1086  \end{equation}  \end{equation}
1087  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $%  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $
1088  horizontal coefficient for biharmonic diffusion. In the simplest case where  horizontal coefficient for biharmonic diffusion. In the simplest case where
1089  the subgrid-scale fluxes of heat and salt are parameterized with constant  the subgrid-scale fluxes of heat and salt are parameterized with constant
1090  horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$,  horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$,
# Line 947  reduces to a diagonal matrix with consta Line 1095  reduces to a diagonal matrix with consta
1095  \begin{array}{ccc}  \begin{array}{ccc}
1096  K_{h} & 0 & 0 \\  K_{h} & 0 & 0 \\
1097  0 & K_{h} & 0 \\  0 & K_{h} & 0 \\
1098  0 & 0 & K_{v}%  0 & 0 & K_{v}
1099  \end{array}  \end{array}
1100  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}
1101  \end{equation}  \end{equation}
# Line 957  salinity ... ). Line 1105  salinity ... ).
1105    
1106  \subsection{Vector invariant form}  \subsection{Vector invariant form}
1107    
1108  For some purposes it is advantageous to write momentum advection in eq(\ref%  For some purposes it is advantageous to write momentum advection in
1109  {hor-mtm}) and (\ref{vertmtm}) in the (so-called) `vector invariant' form:  eq(\ref {eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the
1110    (so-called) `vector invariant' form:
1111    
1112  \begin{equation}  \begin{equation}
1113  \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}
1114  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla %  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla
1115  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]
1116  \label{eq:vi-identity}  \label{eq:vi-identity}
1117  \end{equation}%  \end{equation}
1118  This permits alternative numerical treatments of the non-linear terms based  This permits alternative numerical treatments of the non-linear terms based
1119  on their representation as a vorticity flux. Because gradients of coordinate  on their representation as a vorticity flux. Because gradients of coordinate
1120  vectors no longer appear on the rhs of (\ref{eq:vi-identity}), explicit  vectors no longer appear on the rhs of (\ref{eq:vi-identity}), explicit
1121  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref%  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref
1122  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information
1123  about the geometry is contained in the areas and lengths of the volumes used  about the geometry is contained in the areas and lengths of the volumes used
1124  to discretize the model.  to discretize the model.
1125    
1126  \subsection{Adjoint}  \subsection{Adjoint}
1127    
1128  Tangent linear and adjoint counterparts of the forward model and described  Tangent linear and adjoint counterparts of the forward model are described
1129  in Chapter 5.  in Chapter 5.
1130    
1131  % $Header$  % $Header$
# Line 991  coordinates} Line 1140  coordinates}
1140    
1141  The hydrostatic primitive equations (HPEs) in p-coordinates are:  The hydrostatic primitive equations (HPEs) in p-coordinates are:
1142  \begin{eqnarray}  \begin{eqnarray}
1143  \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}}
1144  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}
1145  \label{eq:atmos-mom} \\  \label{eq:atmos-mom} \\
1146  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\
1147  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1148  \partial p} &=&0  \label{eq:atmos-cont} \\  \partial p} &=&0  \label{eq:atmos-cont} \\
1149  p\alpha &=&RT  \label{eq:atmos-eos} \\  p\alpha &=&RT  \label{eq:atmos-eos} \\
1150  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}
1151  \end{eqnarray}%  \end{eqnarray}
1152  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
1153  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot
1154  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total
1155  derivative, $f=2\Omega \sin lat$ is the Coriolis parameter, $\phi =gz$ is  derivative, $f=2\Omega \sin \varphi$ is the Coriolis parameter, $\phi =gz$ is
1156  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp%  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp
1157  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref%  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref
1158  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $%  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $
1159  e=c_{v}T$, $T$ is temperature, $Q$ is the rate of heating per unit mass and $%  e=c_{v}T$, $T$ is temperature, $Q$ is the rate of heating per unit mass and $
1160  p\frac{D\alpha }{Dt}$ is the work done by the fluid in compressing.  p\frac{D\alpha }{Dt}$ is the work done by the fluid in compressing.
1161    
1162  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
# Line 1015  $\theta $ so that it looks more like a g Line 1164  $\theta $ so that it looks more like a g
1164  Differentiating (\ref{eq:atmos-eos}) we get:  Differentiating (\ref{eq:atmos-eos}) we get:
1165  \begin{equation*}  \begin{equation*}
1166  p\frac{D\alpha }{Dt}+\alpha \frac{Dp}{Dt}=R\frac{DT}{Dt}  p\frac{D\alpha }{Dt}+\alpha \frac{Dp}{Dt}=R\frac{DT}{Dt}
1167  \end{equation*}%  \end{equation*}
1168  which, when added to the heat equation (\ref{eq:atmos-heat}) and using $%  which, when added to the heat equation (\ref{eq:atmos-heat}) and using $
1169  c_{p}=c_{v}+R$, gives:  c_{p}=c_{v}+R$, gives:
1170  \begin{equation}  \begin{equation}
1171  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}
1172  \label{eq-p-heat-interim}  \label{eq-p-heat-interim}
1173  \end{equation}%  \end{equation}
1174  Potential temperature is defined:  Potential temperature is defined:
1175  \begin{equation}  \begin{equation}
1176  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}
1177  \end{equation}%  \end{equation}
1178  where $p_{c}$ is a reference pressure and $\kappa =R/c_{p}$. For convenience  where $p_{c}$ is a reference pressure and $\kappa =R/c_{p}$. For convenience
1179  we will make use of the Exner function $\Pi (p)$ which defined by:  we will make use of the Exner function $\Pi (p)$ which defined by:
1180  \begin{equation}  \begin{equation}
1181  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}
1182  \end{equation}%  \end{equation}
1183  The following relations will be useful and are easily expressed in terms of  The following relations will be useful and are easily expressed in terms of
1184  the Exner function:  the Exner function:
1185  \begin{equation*}  \begin{equation*}
1186  c_{p}T=\Pi \theta \;\;;\;\;\frac{\partial \Pi }{\partial p}=\frac{\kappa \Pi  c_{p}T=\Pi \theta \;\;;\;\;\frac{\partial \Pi }{\partial p}=\frac{\kappa \Pi
1187  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{%  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{
1188  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}%  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}
1189  \frac{Dp}{Dt}  \frac{Dp}{Dt}
1190  \end{equation*}%  \end{equation*}
1191  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.
1192    
1193  The heat equation is obtained by noting that  The heat equation is obtained by noting that
# Line 1053  and on substituting into (\ref{eq-p-heat Line 1202  and on substituting into (\ref{eq-p-heat
1202  \end{equation}  \end{equation}
1203  which is in conservative form.  which is in conservative form.
1204    
1205  For convenience in the model we prefer to step forward (\ref%  For convenience in the model we prefer to step forward (\ref
1206  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).
1207    
1208  \subsubsection{Boundary conditions}  \subsubsection{Boundary conditions}
# Line 1069  In $p$-coordinates, the upper boundary a Line 1218  In $p$-coordinates, the upper boundary a
1218  surface ($\phi $ is imposed and $\omega \neq 0$).  surface ($\phi $ is imposed and $\omega \neq 0$).
1219    
1220  \subsubsection{Splitting the geo-potential}  \subsubsection{Splitting the geo-potential}
1221    \label{sec:hpe-p-geo-potential-split}
1222    
1223  For the purposes of initialization and reducing round-off errors, the model  For the purposes of initialization and reducing round-off errors, the model
1224  deals with perturbations from reference (or ``standard'') profiles. For  deals with perturbations from reference (or ``standard'') profiles. For
# Line 1097  _{o}(p_{o})=g~Z_{topo}$, defined: Line 1247  _{o}(p_{o})=g~Z_{topo}$, defined:
1247    
1248  The final form of the HPE's in p coordinates is then:  The final form of the HPE's in p coordinates is then:
1249  \begin{eqnarray}  \begin{eqnarray}
1250  \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}}
1251  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}}
1252    \label{eq:atmos-prime} \\
1253  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\
1254  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1255  \partial p} &=&0 \\  \partial p} &=&0 \\
1256  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\
1257  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime}  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }
1258  \end{eqnarray}  \end{eqnarray}
1259    
1260  % $Header$  % $Header$
# Line 1117  We review here the method by which the s Line 1268  We review here the method by which the s
1268  HPE's for the ocean written in z-coordinates are obtained. The  HPE's for the ocean written in z-coordinates are obtained. The
1269  non-Boussinesq equations for oceanic motion are:  non-Boussinesq equations for oceanic motion are:
1270  \begin{eqnarray}  \begin{eqnarray}
1271  \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}}
1272  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\
1273  \epsilon _{nh}\frac{Dw}{Dt}+g+\frac{1}{\rho }\frac{\partial p}{\partial z}  \epsilon _{nh}\frac{Dw}{Dt}+g+\frac{1}{\rho }\frac{\partial p}{\partial z}
1274  &=&\epsilon _{nh}\mathcal{F}_{w} \\  &=&\epsilon _{nh}\mathcal{F}_{w} \\
1275  \frac{1}{\rho }\frac{D\rho }{Dt}+\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}%  \frac{1}{\rho }\frac{D\rho }{Dt}+\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}
1276  _{h}+\frac{\partial w}{\partial z} &=&0 \\  _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\
1277  \rho &=&\rho (\theta ,S,p) \\  \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\
1278  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\
1279  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt}
1280  \end{eqnarray}%  \label{eq:non-boussinesq}
1281    \end{eqnarray}
1282  These equations permit acoustics modes, inertia-gravity waves,  These equations permit acoustics modes, inertia-gravity waves,
1283  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline
1284  mode. As written, they cannot be integrated forward consistently - if we  mode. As written, they cannot be integrated forward consistently - if we
1285  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
1286  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref%  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref
1287  {eq-zns-salt}) and then using (\ref{eq-zns-eos}) to yield $\rho $. It is  {eq-zns-salt}) and then using (\ref{eq-zns-eos}) to yield $\rho $. It is
1288  therefore necessary to manipulate the system as follows. Differentiating the  therefore necessary to manipulate the system as follows. Differentiating the
1289  EOS (equation of state) gives:  EOS (equation of state) gives:
# Line 1143  _{\theta ,p}\frac{DS}{Dt}+\left. \frac{\ Line 1295  _{\theta ,p}\frac{DS}{Dt}+\left. \frac{\
1295  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexpansion}  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexpansion}
1296  \end{equation}  \end{equation}
1297    
1298  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
1299  reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref%  the reciprocal of the sound speed ($c_{s}$) squared. Substituting into
1300  {eq-zns-cont} gives:  \ref{eq-zns-cont} gives:
1301  \begin{equation}  \begin{equation}
1302  \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{
1303  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}
1304  \end{equation}  \end{equation}
1305  where we have used an approximation sign to indicate that we have assumed  where we have used an approximation sign to indicate that we have assumed
# Line 1155  adiabatic motion, dropping the $\frac{D\ Line 1307  adiabatic motion, dropping the $\frac{D\
1307  Replacing \ref{eq-zns-cont} with \ref{eq-zns-pressure} yields a system that  Replacing \ref{eq-zns-cont} with \ref{eq-zns-pressure} yields a system that
1308  can be explicitly integrated forward:  can be explicitly integrated forward:
1309  \begin{eqnarray}  \begin{eqnarray}
1310  \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}}
1311  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1312  \label{eq-cns-hmom} \\  \label{eq-cns-hmom} \\
1313  \epsilon _{nh}\frac{Dw}{Dt}+g+\frac{1}{\rho }\frac{\partial p}{\partial z}  \epsilon _{nh}\frac{Dw}{Dt}+g+\frac{1}{\rho }\frac{\partial p}{\partial z}
1314  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\
1315  \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{
1316  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\
1317  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\
1318  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\
# Line 1174  wherever it appears in a product (ie. no Line 1326  wherever it appears in a product (ie. no
1326  `Boussinesq assumption'. The only term that then retains the full variation  `Boussinesq assumption'. The only term that then retains the full variation
1327  in $\rho $ is the gravitational acceleration:  in $\rho $ is the gravitational acceleration:
1328  \begin{eqnarray}  \begin{eqnarray}
1329  \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}}
1330  _{h}+\frac{1}{\rho _{o}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho _{o}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1331  \label{eq-zcb-hmom} \\  \label{eq-zcb-hmom} \\
1332  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho }{\rho _{o}}+\frac{1}{\rho _{o}}%  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho }{\rho _{o}}+\frac{1}{\rho _{o}}
1333  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1334  \label{eq-zcb-hydro} \\  \label{eq-zcb-hydro} \\
1335  \frac{1}{\rho _{o}c_{s}^{2}}\frac{Dp}{Dt}+\mathbf{\nabla }_{z}\cdot \vec{%  \frac{1}{\rho _{o}c_{s}^{2}}\frac{Dp}{Dt}+\mathbf{\nabla }_{z}\cdot \vec{
1336  \mathbf{v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-zcb-cont} \\  \mathbf{v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-zcb-cont} \\
1337  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\
1338  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\
1339  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}
1340  \end{eqnarray}  \end{eqnarray}
1341  These equations still retain acoustic modes. But, because the  These equations still retain acoustic modes. But, because the
1342  ``compressible'' terms are linearized, the pressure equation \ref%  ``compressible'' terms are linearized, the pressure equation \ref
1343  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent
1344  term appears as a Helmholtz term in the non-hydrostatic pressure equation).  term appears as a Helmholtz term in the non-hydrostatic pressure equation).
1345  These are the \emph{truly} compressible Boussinesq equations. Note that the  These are the \emph{truly} compressible Boussinesq equations. Note that the
1346  EOS must have the same pressure dependency as the linearized pressure term,  EOS must have the same pressure dependency as the linearized pressure term,
1347  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{%  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{
1348  c_{s}^{2}}$, for consistency.  c_{s}^{2}}$, for consistency.
1349    
1350  \subsubsection{`Anelastic' z-coordinate equations}  \subsubsection{`Anelastic' z-coordinate equations}
1351    
1352  The anelastic approximation filters the acoustic mode by removing the  The anelastic approximation filters the acoustic mode by removing the
1353  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}%  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}
1354  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}%  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}
1355  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between
1356  continuity and EOS. A better solution is to change the dependency on  continuity and EOS. A better solution is to change the dependency on
1357  pressure in the EOS by splitting the pressure into a reference function of  pressure in the EOS by splitting the pressure into a reference function of
# Line 1210  height and a perturbation: Line 1362  height and a perturbation:
1362  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from
1363  differentiating the EOS, the continuity equation then becomes:  differentiating the EOS, the continuity equation then becomes:
1364  \begin{equation*}  \begin{equation*}
1365  \frac{1}{\rho _{o}c_{s}^{2}}\left( \frac{Dp_{o}}{Dt}+\epsilon _{s}\frac{%  \frac{1}{\rho _{o}c_{s}^{2}}\left( \frac{Dp_{o}}{Dt}+\epsilon _{s}\frac{
1366  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+%  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+
1367  \frac{\partial w}{\partial z}=0  \frac{\partial w}{\partial z}=0
1368  \end{equation*}  \end{equation*}
1369  If the time- and space-scales of the motions of interest are longer than  If the time- and space-scales of the motions of interest are longer than
1370  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},%  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},
1371  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and
1372  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{%  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{
1373  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta
1374  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon
1375  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation
1376  and EOS. Expanding $\frac{Dp_{o}(z)}{Dt}=-g\rho _{o}w$ then leads to the  and EOS. Expanding $\frac{Dp_{o}(z)}{Dt}=-g\rho _{o}w$ then leads to the
1377  anelastic continuity equation:  anelastic continuity equation:
1378  \begin{equation}  \begin{equation}
1379  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial w}{\partial z}-%  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial w}{\partial z}-
1380  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}
1381  \end{equation}  \end{equation}
1382  A slightly different route leads to the quasi-Boussinesq continuity equation  A slightly different route leads to the quasi-Boussinesq continuity equation
1383  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+%  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+
1384  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }%  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }
1385  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:
1386  \begin{equation}  \begin{equation}
1387  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{1}{\rho _{o}}\frac{%  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{1}{\rho _{o}}\frac{
1388  \partial \left( \rho _{o}w\right) }{\partial z}=0  \label{eq-za-cont2}  \partial \left( \rho _{o}w\right) }{\partial z}=0  \label{eq-za-cont2}
1389  \end{equation}  \end{equation}
1390  Equations \ref{eq-za-cont1} and \ref{eq-za-cont2} are in fact the same  Equations \ref{eq-za-cont1} and \ref{eq-za-cont2} are in fact the same
# Line 1241  equation if: Line 1393  equation if:
1393  \frac{1}{\rho _{o}}\frac{\partial \rho _{o}}{\partial z}=\frac{-g}{c_{s}^{2}}  \frac{1}{\rho _{o}}\frac{\partial \rho _{o}}{\partial z}=\frac{-g}{c_{s}^{2}}
1394  \end{equation}  \end{equation}
1395  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$
1396  and $S_{o}$ profiles, then the EOS dependency on $p_{o}$ and the term $\frac{%  and $S_{o}$ profiles, then the EOS dependency on $p_{o}$ and the term $\frac{
1397  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The
1398  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are
1399  then:  then:
1400  \begin{eqnarray}  \begin{eqnarray}
1401  \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}}
1402  _{h}+\frac{1}{\rho _{o}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho _{o}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1403  \label{eq-zab-hmom} \\  \label{eq-zab-hmom} \\
1404  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho }{\rho _{o}}+\frac{1}{\rho _{o}}%  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho }{\rho _{o}}+\frac{1}{\rho _{o}}
1405  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1406  \label{eq-zab-hydro} \\  \label{eq-zab-hydro} \\
1407  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{1}{\rho _{o}}\frac{%  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{1}{\rho _{o}}\frac{
1408  \partial \left( \rho _{o}w\right) }{\partial z} &=&0  \label{eq-zab-cont} \\  \partial \left( \rho _{o}w\right) }{\partial z} &=&0  \label{eq-zab-cont} \\
1409  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\
1410  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\
# Line 1265  Here, the objective is to drop the depth Line 1417  Here, the objective is to drop the depth
1417  technically, to also remove the dependence of $\rho $ on $p_{o}$. This would  technically, to also remove the dependence of $\rho $ on $p_{o}$. This would
1418  yield the ``truly'' incompressible Boussinesq equations:  yield the ``truly'' incompressible Boussinesq equations:
1419  \begin{eqnarray}  \begin{eqnarray}
1420  \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}}
1421  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1422  \label{eq-ztb-hmom} \\  \label{eq-ztb-hmom} \\
1423  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho }{\rho _{c}}+\frac{1}{\rho _{c}}%  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho }{\rho _{c}}+\frac{1}{\rho _{c}}
1424  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1425  \label{eq-ztb-hydro} \\  \label{eq-ztb-hydro} \\
1426  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial w}{\partial z}  \mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial w}{\partial z}
# Line 1287  retain compressibility effects in the de Line 1439  retain compressibility effects in the de
1439  density thus:  density thus:
1440  \begin{equation*}  \begin{equation*}
1441  \rho =\rho _{o}+\rho ^{\prime }  \rho =\rho _{o}+\rho ^{\prime }
1442  \end{equation*}%  \end{equation*}
1443  We then assert that variations with depth of $\rho _{o}$ are unimportant  We then assert that variations with depth of $\rho _{o}$ are unimportant
1444  while the compressible effects in $\rho ^{\prime }$ are:  while the compressible effects in $\rho ^{\prime }$ are:
1445  \begin{equation*}  \begin{equation*}
1446  \rho _{o}=\rho _{c}  \rho _{o}=\rho _{c}
1447  \end{equation*}%  \end{equation*}
1448  \begin{equation*}  \begin{equation*}
1449  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}
1450  \end{equation*}%  \end{equation*}
1451  This then yields what we can call the semi-compressible Boussinesq  This then yields what we can call the semi-compressible Boussinesq
1452  equations:  equations:
1453  \begin{eqnarray}  \begin{eqnarray}
1454  \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}}
1455  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{%  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{
1456  \mathcal{F}}}  \label{eq:ocean-mom} \\  \mathcal{F}}}  \label{eq:ocean-mom} \\
1457  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho ^{\prime }}{\rho _{c}}+\frac{1}{\rho  \epsilon _{nh}\frac{Dw}{Dt}+\frac{g\rho ^{\prime }}{\rho _{c}}+\frac{1}{\rho
1458  _{c}}\frac{\partial p^{\prime }}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  _{c}}\frac{\partial p^{\prime }}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
# Line 1311  _{c}}\frac{\partial p^{\prime }}{\partia Line 1463  _{c}}\frac{\partial p^{\prime }}{\partia
1463  \\  \\
1464  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\
1465  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}
1466  \end{eqnarray}%  \end{eqnarray}
1467  Note that the hydrostatic pressure of the resting fluid, including that  Note that the hydrostatic pressure of the resting fluid, including that
1468  associated with $\rho _{c}$, is subtracted out since it has no effect on the  associated with $\rho _{c}$, is subtracted out since it has no effect on the
1469  dynamics.  dynamics.
# Line 1335  In spherical coordinates, the velocity c Line 1487  In spherical coordinates, the velocity c
1487  and vertical direction respectively, are given by (see Fig.2) :  and vertical direction respectively, are given by (see Fig.2) :
1488    
1489  \begin{equation*}  \begin{equation*}
1490  u=r\cos \phi \frac{D\lambda }{Dt}  u=r\cos \varphi \frac{D\lambda }{Dt}
1491  \end{equation*}  \end{equation*}
1492    
1493  \begin{equation*}  \begin{equation*}
1494  v=r\frac{D\phi }{Dt}\qquad  v=r\frac{D\varphi }{Dt}
1495  \end{equation*}  \end{equation*}
 $\qquad \qquad \qquad \qquad $  
1496    
1497  \begin{equation*}  \begin{equation*}
1498  \dot{r}=\frac{Dr}{Dt}  \dot{r}=\frac{Dr}{Dt}
1499  \end{equation*}  \end{equation*}
1500    
1501  Here $\phi $ is the latitude, $\lambda $ the longitude, $r$ the radial  Here $\varphi $ is the latitude, $\lambda $ the longitude, $r$ the radial
1502  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
1503  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.
1504    
1505  The `grad' ($\nabla $) and `div' ($\nabla $.) operators are defined by, in  The `grad' ($\nabla $) and `div' ($\nabla\cdot$) operators are defined by, in
1506  spherical coordinates:  spherical coordinates:
1507    
1508  \begin{equation*}  \begin{equation*}
1509  \nabla \equiv \left( \frac{1}{r\cos \phi }\frac{\partial }{\partial \lambda }%  \nabla \equiv \left( \frac{1}{r\cos \varphi }\frac{\partial }{\partial \lambda }
1510  ,\frac{1}{r}\frac{\partial }{\partial \phi },\frac{\partial }{\partial r}%  ,\frac{1}{r}\frac{\partial }{\partial \varphi },\frac{\partial }{\partial r}
1511  \right)  \right)
1512  \end{equation*}  \end{equation*}
1513    
1514  \begin{equation*}  \begin{equation*}
1515  \nabla .v\equiv \frac{1}{r\cos \phi }\left\{ \frac{\partial u}{\partial  \nabla\cdot v\equiv \frac{1}{r\cos \varphi }\left\{ \frac{\partial u}{\partial
1516  \lambda }+\frac{\partial }{\partial \phi }\left( v\cos \phi \right) \right\}  \lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\}
1517  +\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}
1518  \end{equation*}  \end{equation*}
1519    
1520  %%%% \end{document}  %tci%\end{document}

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