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revision 1.3 by cnh, Wed Oct 10 16:48:45 2001 UTC revision 1.10 by cnh, Tue Nov 13 20:35:51 2001 UTC
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1  % $Header$  % $Header$
2  % $Name$  % $Name$
 %\usepackage{oldgerm}  
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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}
24    %tci%\fancyfoot[RO,LE]{ }
25    %tci%\renewcommand{\headrulewidth}{0.4pt}
26    %tci%\renewcommand{\footrulewidth}{0.4pt}
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    
# Line 77  MITgcm has a number of novel aspects: Line 54  MITgcm has a number of novel aspects:
54  \begin{itemize}  \begin{itemize}
55  \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
56  hydrodynamical kernel is used to drive forward both atmospheric and oceanic  hydrodynamical kernel is used to drive forward both atmospheric and oceanic
57  models - see fig%  models - see fig \ref{fig:onemodel}
 \marginpar{  
 Fig.1 One model}\ref{fig:onemodel}  
58    
59  %% CNHbegin  %% CNHbegin
60  \input{part1/one_model_figure}  \input{part1/one_model_figure}
61  %% CNHend  %% CNHend
62    
63  \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
64  small-scale and large scale processes - see fig %  small-scale and large scale processes - see fig \ref{fig:all-scales}
 \marginpar{  
 Fig.2 All scales}\ref{fig:all-scales}  
65    
66  %% CNHbegin  %% CNHbegin
67  \input{part1/all_scales_figure}  \input{part1/all_scales_figure}
# Line 96  Fig.2 All scales}\ref{fig:all-scales} Line 69  Fig.2 All scales}\ref{fig:all-scales}
69    
70  \item finite volume techniques are employed yielding an intuitive  \item finite volume techniques are employed yielding an intuitive
71  discretization and support for the treatment of irregular geometries using  discretization and support for the treatment of irregular geometries using
72  orthogonal curvilinear grids and shaved cells - see fig %  orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes}
 \marginpar{  
 Fig.3 Finite volumes}\ref{fig:finite-volumes}  
73    
74  %% CNHbegin  %% CNHbegin
75  \input{part1/fvol_figure}  \input{part1/fvol_figure}
# Line 117  listed in an Appendix. Line 88  listed in an Appendix.
88    
89  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
90  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  
91    
92  % $Header$  % $Header$
93  % $Name$  % $Name$
# Line 126  give a feel for the wide range of proble Line 96  give a feel for the wide range of proble
96    
97  The MITgcm has been designed and used to model a wide range of phenomena,  The MITgcm has been designed and used to model a wide range of phenomena,
98  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
99  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
100  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
101  of them here. A more detailed description of the underlying formulation,  of them here. A more detailed description of the underlying formulation,
102  numerical algorithm and implementation that lie behind these calculations is  numerical algorithm and implementation that lie behind these calculations is
103  given later. Indeed many of the illustrative examples shown below can be  given later. Indeed many of the illustrative examples shown below can be
104  easily reproduced: simply download the model (the minimum you need is a PC  easily reproduced: simply download the model (the minimum you need is a PC
105  running linux, together with a FORTRAN\ 77 compiler) and follow the examples  running Linux, together with a FORTRAN\ 77 compiler) and follow the examples
106  described in detail in the documentation.  described in detail in the documentation.
107    
108  \subsection{Global atmosphere: `Held-Suarez' benchmark}  \subsection{Global atmosphere: `Held-Suarez' benchmark}
109    
110  A novel feature of MITgcm is its ability to simulate both atmospheric and  A novel feature of MITgcm is its ability to simulate, using one basic algorithm,
111  oceanographic flows at both small and large scales.  both atmospheric and oceanographic flows at both small and large scales.
112    
113  Fig.E1a.\ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$  Figure \ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$
114  temperature field obtained using the atmospheric isomorph of MITgcm run at  temperature field obtained using the atmospheric isomorph of MITgcm run at
115  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
116  (blue) and warm air along an equatorial band (red). Fully developed  (blue) and warm air along an equatorial band (red). Fully developed
# Line 156  there are no mountains or land-sea contr Line 126  there are no mountains or land-sea contr
126  %% CNHend  %% CNHend
127    
128  As described in Adcroft (2001), a `cubed sphere' is used to discretize the  As described in Adcroft (2001), a `cubed sphere' is used to discretize the
129  globe permitting a uniform gridding and obviated the need to fourier filter.  globe permitting a uniform griding and obviated the need to Fourier filter.
130  The `vector-invariant' form of MITgcm supports any orthogonal curvilinear  The `vector-invariant' form of MITgcm supports any orthogonal curvilinear
131  grid, of which the cubed sphere is just one of many choices.  grid, of which the cubed sphere is just one of many choices.
132    
133  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
134  wind and meridional overturning streamfunction from a 20-level version of  wind from a 20-level configuration of
135  the model. It compares favorable with more conventional spatial  the model. It compares favorable with more conventional spatial
136  discretization approaches.  discretization approaches. The two plots show the field calculated using the
137    cube-sphere grid and the flow calculated using a regular, spherical polar
138  A regular spherical lat-lon grid can also be used.  latitude-longitude grid. Both grids are supported within the model.
139    
140  %% CNHbegin  %% CNHbegin
141  \input{part1/hs_zave_u_figure}  \input{part1/hs_zave_u_figure}
# Line 181  diffusive patterns of ocean currents. Bu Line 151  diffusive patterns of ocean currents. Bu
151  increased until the baroclinic instability process is resolved, numerical  increased until the baroclinic instability process is resolved, numerical
152  solutions of a different and much more realistic kind, can be obtained.  solutions of a different and much more realistic kind, can be obtained.
153    
154  Fig. ?.? shows the surface temperature and velocity field obtained from  Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity
155  MITgcm run at $\frac{1}{6}^{\circ }$ horizontal resolution on a $lat-lon$  field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal
156    resolution on a $lat-lon$
157  grid in which the pole has been rotated by 90$^{\circ }$ on to the equator  grid in which the pole has been rotated by 90$^{\circ }$ on to the equator
158  (to avoid the converging of meridian in northern latitudes). 21 vertical  (to avoid the converging of meridian in northern latitudes). 21 vertical
159  levels are used in the vertical with a `lopped cell' representation of  levels are used in the vertical with a `lopped cell' representation of
160  topography. The development and propagation of anomalously warm and cold  topography. The development and propagation of anomalously warm and cold
161  eddies can be clearly been seen in the Gulf Stream region. The transport of  eddies can be clearly seen in the Gulf Stream region. The transport of
162  warm water northward by the mean flow of the Gulf Stream is also clearly  warm water northward by the mean flow of the Gulf Stream is also clearly
163  visible.  visible.
164    
# Line 198  visible. Line 169  visible.
169    
170  \subsection{Global ocean circulation}  \subsection{Global ocean circulation}
171    
172  Fig.E2a shows the pattern of ocean currents at the surface of a 4$^{\circ }$  Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean currents at
173    the surface of a 4$^{\circ }$
174  global ocean model run with 15 vertical levels. Lopped cells are used to  global ocean model run with 15 vertical levels. Lopped cells are used to
175  represent topography on a regular $lat-lon$ grid extending from 70$^{\circ  represent topography on a regular $lat-lon$ grid extending from 70$^{\circ
176  }N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with  }N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with
# Line 206  mixed boundary conditions on temperature Line 178  mixed boundary conditions on temperature
178  transfer properties of ocean eddies, convection and mixing is parameterized  transfer properties of ocean eddies, convection and mixing is parameterized
179  in this model.  in this model.
180    
181  Fig.E2b shows the meridional overturning circulation of the global ocean in  Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning
182  Sverdrups.  circulation of the global ocean in Sverdrups.
183    
184  %%CNHbegin  %%CNHbegin
185  \input{part1/global_circ_figure}  \input{part1/global_circ_figure}
# Line 219  Dense plumes generated by localized cool Line 191  Dense plumes generated by localized cool
191  ocean may be influenced by rotation when the deformation radius is smaller  ocean may be influenced by rotation when the deformation radius is smaller
192  than the width of the cooling region. Rather than gravity plumes, the  than the width of the cooling region. Rather than gravity plumes, the
193  mechanism for moving dense fluid down the shelf is then through geostrophic  mechanism for moving dense fluid down the shelf is then through geostrophic
194  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}
195    (blue is cold dense fluid, red is
196  warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to  warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to
197  trigger convection by surface cooling. The cold, dense water falls down the  trigger convection by surface cooling. The cold, dense water falls down the
198  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 238  presence of complex geometry makes it an Line 211  presence of complex geometry makes it an
211  dynamics and mixing in oceanic canyons and ridges driven by large amplitude  dynamics and mixing in oceanic canyons and ridges driven by large amplitude
212  barotropic tidal currents imposed through open boundary conditions.  barotropic tidal currents imposed through open boundary conditions.
213    
214  Fig. ?.? shows the influence of cross-slope topographic variations on  Fig. \ref{fig:boundary-forced-wave} shows the influence of cross-slope
215    topographic variations on
216  internal wave breaking - the cross-slope velocity is in color, the density  internal wave breaking - the cross-slope velocity is in color, the density
217  contoured. The internal waves are excited by application of open boundary  contoured. The internal waves are excited by application of open boundary
218  conditions on the left.\ They propagate to the sloping boundary (represented  conditions on the left. They propagate to the sloping boundary (represented
219  using MITgcm's finite volume spatial discretization) where they break under  using MITgcm's finite volume spatial discretization) where they break under
220  nonhydrostatic dynamics.  nonhydrostatic dynamics.
221    
# Line 255  Forward and tangent linear counterparts Line 229  Forward and tangent linear counterparts
229  `automatic adjoint compiler'. These can be used in parameter sensitivity and  `automatic adjoint compiler'. These can be used in parameter sensitivity and
230  data assimilation studies.  data assimilation studies.
231    
232  As one example of application of the MITgcm adjoint, Fig.E4 maps the  As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity}
233  gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude  maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude
234  of the overturning streamfunction shown in fig?.? at 40$^{\circ }$N and $%  of the overturning stream-function shown in figure \ref{fig:large-scale-circ}
235  \mathcal{H}$ is the air-sea heat flux 100 years before. We see that $J$ is  at 60$^{\circ }$N and $
236    \mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over
237    a 100 year period. We see that $J$ is
238  sensitive to heat fluxes over the Labrador Sea, one of the important sources  sensitive to heat fluxes over the Labrador Sea, one of the important sources
239  of deep water for the thermohaline circulations. This calculation also  of deep water for the thermohaline circulations. This calculation also
240  yields sensitivities to all other model parameters.  yields sensitivities to all other model parameters.
# Line 272  yields sensitivities to all other model Line 248  yields sensitivities to all other model
248  An important application of MITgcm is in state estimation of the global  An important application of MITgcm is in state estimation of the global
249  ocean circulation. An appropriately defined `cost function', which measures  ocean circulation. An appropriately defined `cost function', which measures
250  the departure of the model from observations (both remotely sensed and  the departure of the model from observations (both remotely sensed and
251  insitu) over an interval of time, is minimized by adjusting `control  in-situ) over an interval of time, is minimized by adjusting `control
252  parameters' such as air-sea fluxes, the wind field, the initial conditions  parameters' such as air-sea fluxes, the wind field, the initial conditions
253  etc. Figure ?.? shows an estimate of the time-mean surface elevation of the  etc. Figure \ref{fig:assimilated-globes} shows an estimate of the time-mean
254  ocean obtained by bringing the model in to consistency with altimetric and  surface elevation of the ocean obtained by bringing the model in to
255  in-situ observations over the period 1992-1997.  consistency with altimetric and in-situ observations over the period
256    1992-1997. {\bf CHANGE THIS TEXT - FIG FROM PATRICK/CARL/DETLEF}
257    
258  %% CNHbegin  %% CNHbegin
259  \input{part1/globes_figure}  \input{part1/globes_figure}
# Line 287  in-situ observations over the period 199 Line 264  in-situ observations over the period 199
264  MITgcm is being used to study global biogeochemical cycles in the ocean. For  MITgcm is being used to study global biogeochemical cycles in the ocean. For
265  example one can study the effects of interannual changes in meteorological  example one can study the effects of interannual changes in meteorological
266  forcing and upper ocean circulation on the fluxes of carbon dioxide and  forcing and upper ocean circulation on the fluxes of carbon dioxide and
267  oxygen between the ocean and atmosphere. The figure shows the annual air-sea  oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows
268  flux of oxygen and its relation to density outcrops in the southern oceans  the annual air-sea flux of oxygen and its relation to density outcrops in
269  from a single year of a global, interannually varying simulation.  the southern oceans from a single year of a global, interannually varying
270    simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution
271    telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown).
272    
273  %%CNHbegin  %%CNHbegin
274  \input{part1/biogeo_figure}  \input{part1/biogeo_figure}
# Line 297  from a single year of a global, interann Line 276  from a single year of a global, interann
276    
277  \subsection{Simulations of laboratory experiments}  \subsection{Simulations of laboratory experiments}
278    
279  Figure ?.? shows MITgcm being used to simulate a laboratory experiment  Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a
280  enquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An  laboratory experiment inquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An
281  initially homogeneous tank of water ($1m$ in diameter) is driven from its  initially homogeneous tank of water ($1m$ in diameter) is driven from its
282  free surface by a rotating heated disk. The combined action of mechanical  free surface by a rotating heated disk. The combined action of mechanical
283  and thermal forcing creates a lens of fluid which becomes baroclinically  and thermal forcing creates a lens of fluid which becomes baroclinically
284  unstable. The stratification and depth of penetration of the lens is  unstable. The stratification and depth of penetration of the lens is
285  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
286  stratification of the ACC.  stratification of the ACC.
287    
288  %%CNHbegin  %%CNHbegin
# Line 317  stratification of the ACC. Line 296  stratification of the ACC.
296    
297  To render atmosphere and ocean models from one dynamical core we exploit  To render atmosphere and ocean models from one dynamical core we exploit
298  `isomorphisms' between equation sets that govern the evolution of the  `isomorphisms' between equation sets that govern the evolution of the
299  respective fluids - see fig.4%  respective fluids - see figure \ref{fig:isomorphic-equations}.
300  \marginpar{  One system of hydrodynamical equations is written down
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down  
301  and encoded. The model variables have different interpretations depending on  and encoded. The model variables have different interpretations depending on
302  whether the atmosphere or ocean is being studied. Thus, for example, the  whether the atmosphere or ocean is being studied. Thus, for example, the
303  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are
304  modeling the atmosphere and height, $z$, if we are modeling the ocean.  modeling the atmosphere (left hand side of figure \ref{fig:isomorphic-equations})
305    and height, $z$, if we are modeling the ocean (right hand side of figure
306    \ref{fig:isomorphic-equations}).
307    
308  %%CNHbegin  %%CNHbegin
309  \input{part1/zandpcoord_figure.tex}  \input{part1/zandpcoord_figure.tex}
# Line 335  velocity $\vec{\mathbf{v}}$, active trac Line 315  velocity $\vec{\mathbf{v}}$, active trac
315  depend on $\theta $, $S$, and $p$. The equations that govern the evolution  depend on $\theta $, $S$, and $p$. The equations that govern the evolution
316  of these fields, obtained by applying the laws of classical mechanics and  of these fields, obtained by applying the laws of classical mechanics and
317  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of
318  a generic vertical coordinate, $r$, see fig.5%  a generic vertical coordinate, $r$, so that the appropriate
319  \marginpar{  kinematic boundary conditions can be applied isomorphically
320  Fig.5 The vertical coordinate of model}:  see figure \ref{fig:zandp-vert-coord}.
321    
322  %%CNHbegin  %%CNHbegin
323  \input{part1/vertcoord_figure.tex}  \input{part1/vertcoord_figure.tex}
324  %%CNHend  %%CNHend
325    
326  \begin{equation*}  \begin{equation*}
327  \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}%  \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}
328  \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}%  \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}
329  \text{ horizontal mtm}  \text{ horizontal mtm} \label{eq:horizontal_mtm}
330  \end{equation*}  \end{equation*}
331    
332  \begin{equation*}  \begin{equation}
333  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{%  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{
334  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{
335  vertical mtm}  vertical mtm} \label{eq:vertical_mtm}
336  \end{equation*}  \end{equation}
337    
338  \begin{equation}  \begin{equation}
339  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{%  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{
340  \partial r}=0\text{ continuity}  \label{eq:continuous}  \partial r}=0\text{ continuity}  \label{eq:continuity}
341  \end{equation}  \end{equation}
342    
343  \begin{equation*}  \begin{equation}
344  b=b(\theta ,S,r)\text{ equation of state}  b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state}
345  \end{equation*}  \end{equation}
346    
347  \begin{equation*}  \begin{equation}
348  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}
349  \end{equation*}  \label{eq:potential_temperature}
350    \end{equation}
351    
352  \begin{equation*}  \begin{equation}
353  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}
354  \end{equation*}  \label{eq:humidity_salt}
355    \end{equation}
356    
357  Here:  Here:
358    
# Line 384  is the total derivative} Line 366  is the total derivative}
366  \end{equation*}  \end{equation*}
367    
368  \begin{equation*}  \begin{equation*}
369  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}%  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}
370  \text{ is the `grad' operator}  \text{ is the `grad' operator}
371  \end{equation*}  \end{equation*}
372  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}%  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}
373  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$
374  is a unit vector in the vertical  is a unit vector in the vertical
375    
# Line 421  S\text{ is specific humidity in the atmo Line 403  S\text{ is specific humidity in the atmo
403  \end{equation*}  \end{equation*}
404    
405  \begin{equation*}  \begin{equation*}
406  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{%  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{
407  \mathbf{v}}  \mathbf{v}}
408  \end{equation*}  \end{equation*}
409    
# Line 434  S\text{ is specific humidity in the atmo Line 416  S\text{ is specific humidity in the atmo
416  \end{equation*}  \end{equation*}
417    
418  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
419  extensive `physics' packages for atmosphere and ocean described in Chapter 6.  `physics' and forcing packages for atmosphere and ocean. These are described
420    in later chapters.
421    
422  \subsection{Kinematic Boundary conditions}  \subsection{Kinematic Boundary conditions}
423    
424  \subsubsection{vertical}  \subsubsection{vertical}
425    
426  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}):
427    
428  \begin{equation}  \begin{equation}
429  \dot{r}=0atr=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)}  \dot{r}=0atr=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)}
# Line 449  at fixed and moving $r$ surfaces we set Line 432  at fixed and moving $r$ surfaces we set
432    
433  \begin{equation}  \begin{equation}
434  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \
435  (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc}  (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc}
436  \end{equation}  \end{equation}
437    
438  Here  Here
# Line 466  of motion. Line 449  of motion.
449    
450  \begin{equation}  \begin{equation}
451  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}
452  \end{equation}%  \end{equation}
453  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.
454    
455  \subsection{Atmosphere}  \subsection{Atmosphere}
456    
457  In the atmosphere, see fig.5, we interpret:  In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret:
458    
459  \begin{equation}  \begin{equation}
460  r=p\text{ is the pressure}  \label{eq:atmos-r}  r=p\text{ is the pressure}  \label{eq:atmos-r}
# Line 503  where Line 486  where
486    
487  \begin{equation*}  \begin{equation*}
488  T\text{ is absolute temperature}  T\text{ is absolute temperature}
489  \end{equation*}%  \end{equation*}
490  \begin{equation*}  \begin{equation*}
491  p\text{ is the pressure}  p\text{ is the pressure}
492  \end{equation*}%  \end{equation*}
493  \begin{eqnarray*}  \begin{eqnarray*}
494  &&z\text{ is the height of the pressure surface} \\  &&z\text{ is the height of the pressure surface} \\
495  &&g\text{ is the acceleration due to gravity}  &&g\text{ is the acceleration due to gravity}
# Line 516  In the above the ideal gas law, $p=\rho Line 499  In the above the ideal gas law, $p=\rho
499  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)
500  \begin{equation}  \begin{equation}
501  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}
502  \end{equation}%  \end{equation}
503  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
504  constant and $c_{p}$ the specific heat of air at constant pressure.  constant and $c_{p}$ the specific heat of air at constant pressure.
505    
# Line 542  The boundary conditions at top and botto Line 525  The boundary conditions at top and botto
525  atmosphere)}  \label{eq:moving-bc-atmos}  atmosphere)}  \label{eq:moving-bc-atmos}
526  \end{eqnarray}  \end{eqnarray}
527    
528  Then the (hydrostatic form of) eq(\ref{eq:continuous}) yields a consistent  Then the (hydrostatic form of) equations (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt})
529  set of atmospheric equations which, for convenience, are written out in $p$  yields a consistent set of atmospheric equations which, for convenience, are written out in $p$
530  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).
531    
532  \subsection{Ocean}  \subsection{Ocean}
# Line 566  At the bottom of the ocean: $R_{fixed}(x Line 549  At the bottom of the ocean: $R_{fixed}(x
549    
550  The surface of the ocean is given by: $R_{moving}=\eta $  The surface of the ocean is given by: $R_{moving}=\eta $
551    
552  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 $
553  R_{o}=Z_{o}=0$.  R_{o}=Z_{o}=0$.
554    
555  Boundary conditions are:  Boundary conditions are:
# Line 574  Boundary conditions are: Line 557  Boundary conditions are:
557  \begin{eqnarray}  \begin{eqnarray}
558  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}
559  \\  \\
560  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)
561  \label{eq:moving-bc-ocean}}  \label{eq:moving-bc-ocean}}
562  \end{eqnarray}  \end{eqnarray}
563  where $\eta $ is the elevation of the free surface.  where $\eta $ is the elevation of the free surface.
564    
565  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
566    of oceanic equations
567  which, for convenience, are written out in $z$ coordinates in Appendix Ocean  which, for convenience, are written out in $z$ coordinates in Appendix Ocean
568  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).
569    
# Line 591  Let us separate $\phi $ in to surface, h Line 575  Let us separate $\phi $ in to surface, h
575  \begin{equation}  \begin{equation}
576  \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)
577  \label{eq:phi-split}  \label{eq:phi-split}
578  \end{equation}%  \end{equation}
579  and write eq(\ref{incompressible}a,b) in the form:  and write eq(\ref{eq:incompressible}) in the form:
580    
581  \begin{equation}  \begin{equation}
582  \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 605  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l Line 589  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l
589  \end{equation}  \end{equation}
590    
591  \begin{equation}  \begin{equation}
592  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{%  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{
593  \partial r}=G_{\dot{r}}  \label{eq:mom-w}  \partial r}=G_{\dot{r}}  \label{eq:mom-w}
594  \end{equation}  \end{equation}
595  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.
596    
597  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
598  {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
599  terms in the momentum equations. In spherical coordinates they take the form%  terms in the momentum equations. In spherical coordinates they take the form
600  \footnote{%  \footnote{
601  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms
602  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref%  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref
603  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in
604  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (%  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (
605  \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
606  discussion:  discussion:
607    
# Line 625  discussion: Line 609  discussion:
609  \left.  \left.
610  \begin{tabular}{l}  \begin{tabular}{l}
611  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\
612  $-\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\} $
613  \\  \\
614  $-\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\} $
615  \\  \\
616  $+\mathcal{F}_{u}$%  $+\mathcal{F}_{u}$
617  \end{tabular}%  \end{tabular}
618  \ \right\} \left\{  \ \right\} \left\{
619  \begin{tabular}{l}  \begin{tabular}{l}
620  \textit{advection} \\  \textit{advection} \\
621  \textit{metric} \\  \textit{metric} \\
622  \textit{Coriolis} \\  \textit{Coriolis} \\
623  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
624  \end{tabular}%  \end{tabular}
625  \ \right. \qquad  \label{eq:gu-speherical}  \ \right. \qquad  \label{eq:gu-speherical}
626  \end{equation}  \end{equation}
627    
# Line 645  $+\mathcal{F}_{u}$% Line 629  $+\mathcal{F}_{u}$%
629  \left.  \left.
630  \begin{tabular}{l}  \begin{tabular}{l}
631  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\
632  $-\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\}
633  $ \\  $ \\
634  $-\left\{ -2\Omega u\sin lat\right\} $ \\  $-\left\{ -2\Omega u\sin \varphi \right\} $ \\
635  $+\mathcal{F}_{v}$%  $+\mathcal{F}_{v}$
636  \end{tabular}%  \end{tabular}
637  \ \right\} \left\{  \ \right\} \left\{
638  \begin{tabular}{l}  \begin{tabular}{l}
639  \textit{advection} \\  \textit{advection} \\
640  \textit{metric} \\  \textit{metric} \\
641  \textit{Coriolis} \\  \textit{Coriolis} \\
642  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
643  \end{tabular}%  \end{tabular}
644  \ \right. \qquad  \label{eq:gv-spherical}  \ \right. \qquad  \label{eq:gv-spherical}
645  \end{equation}%  \end{equation}
646  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
647    
648  \begin{equation}  \begin{equation}
# Line 666  $+\mathcal{F}_{v}$% Line 650  $+\mathcal{F}_{v}$%
650  \begin{tabular}{l}  \begin{tabular}{l}
651  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\
652  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\
653  ${+}\underline{{2\Omega u\cos lat}}$ \\  ${+}\underline{{2\Omega u\cos \varphi}}$ \\
654  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$%  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$
655  \end{tabular}%  \end{tabular}
656  \ \right\} \left\{  \ \right\} \left\{
657  \begin{tabular}{l}  \begin{tabular}{l}
658  \textit{advection} \\  \textit{advection} \\
659  \textit{metric} \\  \textit{metric} \\
660  \textit{Coriolis} \\  \textit{Coriolis} \\
661  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
662  \end{tabular}%  \end{tabular}
663  \ \right.  \label{eq:gw-spherical}  \ \right.  \label{eq:gw-spherical}
664  \end{equation}%  \end{equation}
665  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
666    
667  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 `$\varphi$
668  ' is latitude.  ' is latitude.
669    
670  Grad and div operators in spherical coordinates are defined in appendix  Grad and div operators in spherical coordinates are defined in appendix
671  OPERATORS.%  OPERATORS.
 \marginpar{  
 Fig.6 Spherical polar coordinate system.}  
672    
673  %%CNHbegin  %%CNHbegin
674  \input{part1/sphere_coord_figure.tex}  \input{part1/sphere_coord_figure.tex}
# Line 700  hydrostatic balance and the `traditional Line 682  hydrostatic balance and the `traditional
682  Coriolis force is treated approximately and the shallow atmosphere  Coriolis force is treated approximately and the shallow atmosphere
683  approximation is made.\ The MITgcm need not make the `traditional  approximation is made.\ The MITgcm need not make the `traditional
684  approximation'. To be able to support consistent non-hydrostatic forms the  approximation'. To be able to support consistent non-hydrostatic forms the
685  shallow atmosphere approximation can be relaxed - when dividing through by $%  shallow atmosphere approximation can be relaxed - when dividing through by $
686  r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$,  r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$,
687  the radius of the earth.  the radius of the earth.
688    
689  \subsubsection{Hydrostatic and quasi-hydrostatic forms}  \subsubsection{Hydrostatic and quasi-hydrostatic forms}
690    \label{sec:hydrostatic_and_quasi-hydrostatic_forms}
691    
692  These are discussed at length in Marshall et al (1997a).  These are discussed at length in Marshall et al (1997a).
693    
# Line 713  terms in Eqs. (\ref{eq:gu-speherical} $\ Line 696  terms in Eqs. (\ref{eq:gu-speherical} $\
696  are neglected and `${r}$' is replaced by `$a$', the mean radius of the  are neglected and `${r}$' is replaced by `$a$', the mean radius of the
697  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
698  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
699  computed at all other levels by integration of the hydrostatic relation, eq(%  computed at all other levels by integration of the hydrostatic relation, eq(
700  \ref{eq:hydrostatic}).  \ref{eq:hydrostatic}).
701    
702  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between
703  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
704  \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
705  contribution to the pressure field: only the terms underlined twice in Eqs. (%  contribution to the pressure field: only the terms underlined twice in Eqs. (
706  \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
707  and, simultaneously, the shallow atmosphere approximation is relaxed. In  and, simultaneously, the shallow atmosphere approximation is relaxed. In
708  \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 727  variation of the radial position of a pa Line 710  variation of the radial position of a pa
710  vertical momentum equation (\ref{eq:mom-w}) becomes:  vertical momentum equation (\ref{eq:mom-w}) becomes:
711    
712  \begin{equation*}  \begin{equation*}
713  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos lat  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos \varphi
714  \end{equation*}  \end{equation*}
715  making a small correction to the hydrostatic pressure.  making a small correction to the hydrostatic pressure.
716    
# Line 743  only a quasi-non-hydrostatic atmospheric Line 726  only a quasi-non-hydrostatic atmospheric
726    
727  \paragraph{Non-hydrostatic Ocean}  \paragraph{Non-hydrostatic Ocean}
728    
729  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref%  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref
730  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A
731  three dimensional elliptic equation must be solved subject to Neumann  three dimensional elliptic equation must be solved subject to Neumann
732  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
733  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
734  incompressible condition eq(\ref{eq:continuous})c has already filtered out  incompressible condition eq(\ref{eq:continuity}) has already filtered out
735  acoustic modes. It does, however, ensure that the gravity waves are treated  acoustic modes. It does, however, ensure that the gravity waves are treated
736  accurately with an exact dispersion relation. The \textbf{NH} set has a  accurately with an exact dispersion relation. The \textbf{NH} set has a
737  complete angular momentum principle and consistent energetics - see White  complete angular momentum principle and consistent energetics - see White
# Line 756  and Bromley, 1995; Marshall et.al.\ 1997 Line 739  and Bromley, 1995; Marshall et.al.\ 1997
739    
740  \paragraph{Quasi-nonhydrostatic Atmosphere}  \paragraph{Quasi-nonhydrostatic Atmosphere}
741    
742  In the non-hydrostatic version of our atmospheric model we approximate $\dot{%  In the non-hydrostatic version of our atmospheric model we approximate $\dot{
743  r}$ 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})
744  (but only here) by:  (but only here) by:
745    
746  \begin{equation}  \begin{equation}
747  \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}
748  \end{equation}%  \end{equation}
749  where $p_{hy}$ is the hydrostatic pressure.  where $p_{hy}$ is the hydrostatic pressure.
750    
751  \subsubsection{Summary of equation sets supported by model}  \subsubsection{Summary of equation sets supported by model}
# Line 790  equations in $z-$coordinates are support Line 773  equations in $z-$coordinates are support
773    
774  \subparagraph{Non-hydrostatic}  \subparagraph{Non-hydrostatic}
775    
776  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$%  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$
777  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref%  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref
778  {eq:ocean-salt}).  {eq:ocean-salt}).
779    
780  \subsection{Solution strategy}  \subsection{Solution strategy}
781    
782  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{
783  NH} models is summarized in Fig.7.%  NH} models is summarized in Figure \ref{fig:solution-strategy}.
784  \marginpar{  Under all dynamics, a 2-d elliptic equation is
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is  
785  first solved to find the surface pressure and the hydrostatic pressure at  first solved to find the surface pressure and the hydrostatic pressure at
786  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
787  \textbf{QH} dynamics, the horizontal momentum equations are then stepped  \textbf{QH} dynamics, the horizontal momentum equations are then stepped
# Line 813  stepping forward the vertical momentum e Line 795  stepping forward the vertical momentum e
795  %%CNHend  %%CNHend
796    
797  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
798  course, some complication that goes with the inclusion of $\cos \phi \ $%  course, some complication that goes with the inclusion of $\cos \varphi \ $
799  Coriolis terms and the relaxation of the shallow atmosphere approximation.  Coriolis terms and the relaxation of the shallow atmosphere approximation.
800  But this leads to negligible increase in computation. In \textbf{NH}, in  But this leads to negligible increase in computation. In \textbf{NH}, in
801  contrast, one additional elliptic equation - a three-dimensional one - must  contrast, one additional elliptic equation - a three-dimensional one - must
# Line 823  Marshall et al, 1997) resulting in a non Line 805  Marshall et al, 1997) resulting in a non
805  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.
806    
807  \subsection{Finding the pressure field}  \subsection{Finding the pressure field}
808    \label{sec:finding_the_pressure_field}
809    
810  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the
811  pressure field must be obtained diagnostically. We proceed, as before, by  pressure field must be obtained diagnostically. We proceed, as before, by
# Line 837  Hydrostatic pressure is obtained by inte Line 820  Hydrostatic pressure is obtained by inte
820  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:
821    
822  \begin{equation*}  \begin{equation*}
823  \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}
824  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr
825  \end{equation*}  \end{equation*}
826  and so  and so
# Line 855  atmospheric pressure pushing down on the Line 838  atmospheric pressure pushing down on the
838    
839  \subsubsection{Surface pressure}  \subsubsection{Surface pressure}
840    
841  The surface pressure equation can be obtained by integrating continuity, (%  The surface pressure equation can be obtained by integrating continuity,
842  \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$  (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$
843    
844  \begin{equation*}  \begin{equation*}
845  \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}
846  }_{h}+\partial _{r}\dot{r}\right) dr=0  }_{h}+\partial _{r}\dot{r}\right) dr=0
847  \end{equation*}  \end{equation*}
848    
# Line 867  Thus: Line 850  Thus:
850    
851  \begin{equation*}  \begin{equation*}
852  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta
853  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}%  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}
854  _{h}dr=0  _{h}dr=0
855  \end{equation*}  \end{equation*}
856  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 $
857  r $. The above can be rearranged to yield, using Leibnitz's theorem:  r $. The above can be rearranged to yield, using Leibnitz's theorem:
858    
859  \begin{equation}  \begin{equation}
860  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot
861  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}
862  \label{eq:free-surface}  \label{eq:free-surface}
863  \end{equation}%  \end{equation}
864  where we have incorporated a source term.  where we have incorporated a source term.
865    
866  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential
867  (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can  (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can
868  be written  be written
869  \begin{equation}  \begin{equation}
870  \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)
871  \label{eq:phi-surf}  \label{eq:phi-surf}
872  \end{equation}%  \end{equation}
873  where $b_{s}$ is the buoyancy at the surface.  where $b_{s}$ is the buoyancy at the surface.
874    
875  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
876  {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
877  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free
878  surface' and `rigid lid' approaches are available.  surface' and `rigid lid' approaches are available.
879    
880  \subsubsection{Non-hydrostatic pressure}  \subsubsection{Non-hydrostatic pressure}
881    
882  Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{%  Taking the horizontal divergence of (\ref{eq:mom-h}) and adding
883  \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation  $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation
884  (\ref{incompressible}), we deduce that:  (\ref{eq:continuity}), we deduce that:
885    
886  \begin{equation}  \begin{equation}
887  \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{
888  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .%  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .
889  \vec{\mathbf{F}}  \label{eq:3d-invert}  \vec{\mathbf{F}}  \label{eq:3d-invert}
890  \end{equation}  \end{equation}
891    
# Line 922  coasts (in the ocean) and the bottom: Line 905  coasts (in the ocean) and the bottom:
905  \end{equation}  \end{equation}
906  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
907  kinematic condition (\ref{nonormalflow}) is also applied to the vertical  kinematic condition (\ref{nonormalflow}) is also applied to the vertical
908  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 $
909  \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
910  tangential component of velocity, $v_{T}$, at all solid boundaries,  tangential component of velocity, $v_{T}$, at all solid boundaries,
911  depending on the form chosen for the dissipative terms in the momentum  depending on the form chosen for the dissipative terms in the momentum
912  equations - see below.  equations - see below.
913    
914  Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that:  Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that:
915    
916  \begin{equation}  \begin{equation}
917  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}
# Line 939  where Line 922  where
922  \begin{equation*}  \begin{equation*}
923  \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
924  _{s}+\mathbf{\nabla }\phi _{hyd}\right)  _{s}+\mathbf{\nabla }\phi _{hyd}\right)
925  \end{equation*}%  \end{equation*}
926  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem
927  (\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
928  exploit classical 3D potential theory and, by introducing an appropriately  exploit classical 3D potential theory and, by introducing an appropriately
929  chosen $\delta $-function sheet of `source-charge', replace the  chosen $\delta $-function sheet of `source-charge', replace the
930  inhomogeneous boundary condition on pressure by a homogeneous one. The  inhomogeneous boundary condition on pressure by a homogeneous one. The
931  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 $
932  \vec{\mathbf{F}}.$ By simultaneously setting $%  \vec{\mathbf{F}}.$ By simultaneously setting $
933  \begin{array}{l}  \begin{array}{l}
934  \widehat{n}.\vec{\mathbf{F}}%  \widehat{n}.\vec{\mathbf{F}}
935  \end{array}%  \end{array}
936  =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
937  self-consistent but simpler homogenized Elliptic problem is obtained:  self-consistent but simpler homogenized Elliptic problem is obtained:
938    
939  \begin{equation*}  \begin{equation*}
940  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad
941  \end{equation*}%  \end{equation*}
942  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such
943  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
944  {eq:inhom-neumann-nh}) the modified boundary condition becomes:  {eq:inhom-neumann-nh}) the modified boundary condition becomes:
945    
946  \begin{equation}  \begin{equation}
# Line 968  If the flow is `close' to hydrostatic ba Line 951  If the flow is `close' to hydrostatic ba
951  converges rapidly because $\phi _{nh}\ $is then only a small correction to  converges rapidly because $\phi _{nh}\ $is then only a small correction to
952  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).
953    
954  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})
955  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.
956    
957  \subsection{Forcing/dissipation}  \subsection{Forcing/dissipation}
# Line 976  does not vanish at $r=R_{moving}$, and s Line 959  does not vanish at $r=R_{moving}$, and s
959  \subsubsection{Forcing}  \subsubsection{Forcing}
960    
961  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
962  `physics packages' described in detail in chapter ??.  `physics packages' and forcing packages. These are described later on.
963    
964  \subsubsection{Dissipation}  \subsubsection{Dissipation}
965    
# Line 986  Many forms of momentum dissipation are a Line 969  Many forms of momentum dissipation are a
969  biharmonic frictions are commonly used:  biharmonic frictions are commonly used:
970    
971  \begin{equation}  \begin{equation}
972  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}}
973  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}
974  \end{equation}  \end{equation}
975  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 997  friction. These coefficients are the sam Line 980  friction. These coefficients are the sam
980    
981  The mixing terms for the temperature and salinity equations have a similar  The mixing terms for the temperature and salinity equations have a similar
982  form to that of momentum except that the diffusion tensor can be  form to that of momentum except that the diffusion tensor can be
983  non-diagonal and have varying coefficients. $\qquad $%  non-diagonal and have varying coefficients. $\qquad $
984  \begin{equation}  \begin{equation}
985  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
986  _{h}^{4}(T,S)  \label{eq:diffusion}  _{h}^{4}(T,S)  \label{eq:diffusion}
987  \end{equation}  \end{equation}
988  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $%  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $
989  horizontal coefficient for biharmonic diffusion. In the simplest case where  horizontal coefficient for biharmonic diffusion. In the simplest case where
990  the subgrid-scale fluxes of heat and salt are parameterized with constant  the subgrid-scale fluxes of heat and salt are parameterized with constant
991  horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$,  horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$,
# Line 1013  reduces to a diagonal matrix with consta Line 996  reduces to a diagonal matrix with consta
996  \begin{array}{ccc}  \begin{array}{ccc}
997  K_{h} & 0 & 0 \\  K_{h} & 0 & 0 \\
998  0 & K_{h} & 0 \\  0 & K_{h} & 0 \\
999  0 & 0 & K_{v}%  0 & 0 & K_{v}
1000  \end{array}  \end{array}
1001  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}
1002  \end{equation}  \end{equation}
# Line 1023  salinity ... ). Line 1006  salinity ... ).
1006    
1007  \subsection{Vector invariant form}  \subsection{Vector invariant form}
1008    
1009  For some purposes it is advantageous to write momentum advection in eq(\ref%  For some purposes it is advantageous to write momentum advection in eq(\ref
1010  {hor-mtm}) and (\ref{vertmtm}) in the (so-called) `vector invariant' form:  {eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the (so-called) `vector invariant' form:
1011    
1012  \begin{equation}  \begin{equation}
1013  \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}
1014  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla %  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla
1015  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]
1016  \label{eq:vi-identity}  \label{eq:vi-identity}
1017  \end{equation}%  \end{equation}
1018  This permits alternative numerical treatments of the non-linear terms based  This permits alternative numerical treatments of the non-linear terms based
1019  on their representation as a vorticity flux. Because gradients of coordinate  on their representation as a vorticity flux. Because gradients of coordinate
1020  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
1021  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref%  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref
1022  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information
1023  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
1024  to discretize the model.  to discretize the model.
1025    
1026  \subsection{Adjoint}  \subsection{Adjoint}
1027    
1028  Tangent linear and adjoint counterparts of the forward model and described  Tangent linear and adjoint counterparts of the forward model are described
1029  in Chapter 5.  in Chapter 5.
1030    
1031  % $Header$  % $Header$
# Line 1057  coordinates} Line 1040  coordinates}
1040    
1041  The hydrostatic primitive equations (HPEs) in p-coordinates are:  The hydrostatic primitive equations (HPEs) in p-coordinates are:
1042  \begin{eqnarray}  \begin{eqnarray}
1043  \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}}
1044  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}
1045  \label{eq:atmos-mom} \\  \label{eq:atmos-mom} \\
1046  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\
1047  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1048  \partial p} &=&0  \label{eq:atmos-cont} \\  \partial p} &=&0  \label{eq:atmos-cont} \\
1049  p\alpha &=&RT  \label{eq:atmos-eos} \\  p\alpha &=&RT  \label{eq:atmos-eos} \\
1050  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}
1051  \end{eqnarray}%  \end{eqnarray}
1052  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
1053  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot
1054  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total
1055  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
1056  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp%  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp
1057  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref%  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref
1058  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $%  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $
1059  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 $
1060  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.
1061    
1062  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 1081  $\theta $ so that it looks more like a g Line 1064  $\theta $ so that it looks more like a g
1064  Differentiating (\ref{eq:atmos-eos}) we get:  Differentiating (\ref{eq:atmos-eos}) we get:
1065  \begin{equation*}  \begin{equation*}
1066  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}
1067  \end{equation*}%  \end{equation*}
1068  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 $
1069  c_{p}=c_{v}+R$, gives:  c_{p}=c_{v}+R$, gives:
1070  \begin{equation}  \begin{equation}
1071  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}
1072  \label{eq-p-heat-interim}  \label{eq-p-heat-interim}
1073  \end{equation}%  \end{equation}
1074  Potential temperature is defined:  Potential temperature is defined:
1075  \begin{equation}  \begin{equation}
1076  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}
1077  \end{equation}%  \end{equation}
1078  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
1079  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:
1080  \begin{equation}  \begin{equation}
1081  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}
1082  \end{equation}%  \end{equation}
1083  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
1084  the Exner function:  the Exner function:
1085  \begin{equation*}  \begin{equation*}
1086  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
1087  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{%  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{
1088  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}%  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}
1089  \frac{Dp}{Dt}  \frac{Dp}{Dt}
1090  \end{equation*}%  \end{equation*}
1091  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.
1092    
1093  The heat equation is obtained by noting that  The heat equation is obtained by noting that
# Line 1119  and on substituting into (\ref{eq-p-heat Line 1102  and on substituting into (\ref{eq-p-heat
1102  \end{equation}  \end{equation}
1103  which is in conservative form.  which is in conservative form.
1104    
1105  For convenience in the model we prefer to step forward (\ref%  For convenience in the model we prefer to step forward (\ref
1106  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).
1107    
1108  \subsubsection{Boundary conditions}  \subsubsection{Boundary conditions}
# Line 1163  _{o}(p_{o})=g~Z_{topo}$, defined: Line 1146  _{o}(p_{o})=g~Z_{topo}$, defined:
1146    
1147  The final form of the HPE's in p coordinates is then:  The final form of the HPE's in p coordinates is then:
1148  \begin{eqnarray}  \begin{eqnarray}
1149  \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}}
1150  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \label{eq:atmos-prime} \\
1151  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\
1152  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1153  \partial p} &=&0 \\  \partial p} &=&0 \\
1154  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\
1155  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime}  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }
1156  \end{eqnarray}  \end{eqnarray}
1157    
1158  % $Header$  % $Header$
# Line 1183  We review here the method by which the s Line 1166  We review here the method by which the s
1166  HPE's for the ocean written in z-coordinates are obtained. The  HPE's for the ocean written in z-coordinates are obtained. The
1167  non-Boussinesq equations for oceanic motion are:  non-Boussinesq equations for oceanic motion are:
1168  \begin{eqnarray}  \begin{eqnarray}
1169  \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}}
1170  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\
1171  \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}
1172  &=&\epsilon _{nh}\mathcal{F}_{w} \\  &=&\epsilon _{nh}\mathcal{F}_{w} \\
1173  \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}}
1174  _{h}+\frac{\partial w}{\partial z} &=&0 \\  _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\
1175  \rho &=&\rho (\theta ,S,p) \\  \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\
1176  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\
1177  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt}
1178  \end{eqnarray}%  \label{eq:non-boussinesq}
1179    \end{eqnarray}
1180  These equations permit acoustics modes, inertia-gravity waves,  These equations permit acoustics modes, inertia-gravity waves,
1181  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline
1182  mode. As written, they cannot be integrated forward consistently - if we  mode. As written, they cannot be integrated forward consistently - if we
1183  step $\rho $ forward in (\ref{eq-zns-cont}), the answer will not be  step $\rho $ forward in (\ref{eq-zns-cont}), the answer will not be
1184  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref%  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref
1185  {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
1186  therefore necessary to manipulate the system as follows. Differentiating the  therefore necessary to manipulate the system as follows. Differentiating the
1187  EOS (equation of state) gives:  EOS (equation of state) gives:
# Line 1210  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp Line 1194  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp
1194  \end{equation}  \end{equation}
1195    
1196  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 the
1197  reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref%  reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref{eq-zns-cont} gives:
 {eq-zns-cont} gives:  
1198  \begin{equation}  \begin{equation}
1199  \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{
1200  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}
1201  \end{equation}  \end{equation}
1202  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 1221  adiabatic motion, dropping the $\frac{D\ Line 1204  adiabatic motion, dropping the $\frac{D\
1204  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
1205  can be explicitly integrated forward:  can be explicitly integrated forward:
1206  \begin{eqnarray}  \begin{eqnarray}
1207  \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}}
1208  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1209  \label{eq-cns-hmom} \\  \label{eq-cns-hmom} \\
1210  \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}
1211  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\
1212  \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{
1213  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\
1214  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\
1215  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\
# Line 1240  wherever it appears in a product (ie. no Line 1223  wherever it appears in a product (ie. no
1223  `Boussinesq assumption'. The only term that then retains the full variation  `Boussinesq assumption'. The only term that then retains the full variation
1224  in $\rho $ is the gravitational acceleration:  in $\rho $ is the gravitational acceleration:
1225  \begin{eqnarray}  \begin{eqnarray}
1226  \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}}
1227  _{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}}}
1228  \label{eq-zcb-hmom} \\  \label{eq-zcb-hmom} \\
1229  \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}}
1230  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1231  \label{eq-zcb-hydro} \\  \label{eq-zcb-hydro} \\
1232  \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{
1233  \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} \\
1234  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\
1235  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\
1236  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}
1237  \end{eqnarray}  \end{eqnarray}
1238  These equations still retain acoustic modes. But, because the  These equations still retain acoustic modes. But, because the
1239  ``compressible'' terms are linearized, the pressure equation \ref%  ``compressible'' terms are linearized, the pressure equation \ref
1240  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent
1241  term appears as a Helmholtz term in the non-hydrostatic pressure equation).  term appears as a Helmholtz term in the non-hydrostatic pressure equation).
1242  These are the \emph{truly} compressible Boussinesq equations. Note that the  These are the \emph{truly} compressible Boussinesq equations. Note that the
1243  EOS must have the same pressure dependency as the linearized pressure term,  EOS must have the same pressure dependency as the linearized pressure term,
1244  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{%  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{
1245  c_{s}^{2}}$, for consistency.  c_{s}^{2}}$, for consistency.
1246    
1247  \subsubsection{`Anelastic' z-coordinate equations}  \subsubsection{`Anelastic' z-coordinate equations}
1248    
1249  The anelastic approximation filters the acoustic mode by removing the  The anelastic approximation filters the acoustic mode by removing the
1250  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}%  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}
1251  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}%  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}
1252  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between
1253  continuity and EOS. A better solution is to change the dependency on  continuity and EOS. A better solution is to change the dependency on
1254  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 1276  height and a perturbation: Line 1259  height and a perturbation:
1259  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from
1260  differentiating the EOS, the continuity equation then becomes:  differentiating the EOS, the continuity equation then becomes:
1261  \begin{equation*}  \begin{equation*}
1262  \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{
1263  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+%  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+
1264  \frac{\partial w}{\partial z}=0  \frac{\partial w}{\partial z}=0
1265  \end{equation*}  \end{equation*}
1266  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
1267  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},%  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},
1268  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and
1269  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{%  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{
1270  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta
1271  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon
1272  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation
1273  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
1274  anelastic continuity equation:  anelastic continuity equation:
1275  \begin{equation}  \begin{equation}
1276  \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}-
1277  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}
1278  \end{equation}  \end{equation}
1279  A slightly different route leads to the quasi-Boussinesq continuity equation  A slightly different route leads to the quasi-Boussinesq continuity equation
1280  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+%  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+
1281  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }%  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }
1282  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:
1283  \begin{equation}  \begin{equation}
1284  \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{
1285  \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}
1286  \end{equation}  \end{equation}
1287  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 1307  equation if: Line 1290  equation if:
1290  \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}}
1291  \end{equation}  \end{equation}
1292  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$
1293  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 $\frac{
1294  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The
1295  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are
1296  then:  then:
1297  \begin{eqnarray}  \begin{eqnarray}
1298  \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}}
1299  _{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}}}
1300  \label{eq-zab-hmom} \\  \label{eq-zab-hmom} \\
1301  \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}}
1302  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1303  \label{eq-zab-hydro} \\  \label{eq-zab-hydro} \\
1304  \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{
1305  \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} \\
1306  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\
1307  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\
# Line 1331  Here, the objective is to drop the depth Line 1314  Here, the objective is to drop the depth
1314  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
1315  yield the ``truly'' incompressible Boussinesq equations:  yield the ``truly'' incompressible Boussinesq equations:
1316  \begin{eqnarray}  \begin{eqnarray}
1317  \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}}
1318  _{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}}}
1319  \label{eq-ztb-hmom} \\  \label{eq-ztb-hmom} \\
1320  \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}}
1321  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1322  \label{eq-ztb-hydro} \\  \label{eq-ztb-hydro} \\
1323  \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 1353  retain compressibility effects in the de Line 1336  retain compressibility effects in the de
1336  density thus:  density thus:
1337  \begin{equation*}  \begin{equation*}
1338  \rho =\rho _{o}+\rho ^{\prime }  \rho =\rho _{o}+\rho ^{\prime }
1339  \end{equation*}%  \end{equation*}
1340  We then assert that variations with depth of $\rho _{o}$ are unimportant  We then assert that variations with depth of $\rho _{o}$ are unimportant
1341  while the compressible effects in $\rho ^{\prime }$ are:  while the compressible effects in $\rho ^{\prime }$ are:
1342  \begin{equation*}  \begin{equation*}
1343  \rho _{o}=\rho _{c}  \rho _{o}=\rho _{c}
1344  \end{equation*}%  \end{equation*}
1345  \begin{equation*}  \begin{equation*}
1346  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}
1347  \end{equation*}%  \end{equation*}
1348  This then yields what we can call the semi-compressible Boussinesq  This then yields what we can call the semi-compressible Boussinesq
1349  equations:  equations:
1350  \begin{eqnarray}  \begin{eqnarray}
1351  \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}}
1352  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{%  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{
1353  \mathcal{F}}}  \label{eq:ocean-mom} \\  \mathcal{F}}}  \label{eq:ocean-mom} \\
1354  \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
1355  _{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 1377  _{c}}\frac{\partial p^{\prime }}{\partia Line 1360  _{c}}\frac{\partial p^{\prime }}{\partia
1360  \\  \\
1361  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\
1362  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}
1363  \end{eqnarray}%  \end{eqnarray}
1364  Note that the hydrostatic pressure of the resting fluid, including that  Note that the hydrostatic pressure of the resting fluid, including that
1365  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
1366  dynamics.  dynamics.
# Line 1401  In spherical coordinates, the velocity c Line 1384  In spherical coordinates, the velocity c
1384  and vertical direction respectively, are given by (see Fig.2) :  and vertical direction respectively, are given by (see Fig.2) :
1385    
1386  \begin{equation*}  \begin{equation*}
1387  u=r\cos \phi \frac{D\lambda }{Dt}  u=r\cos \varphi \frac{D\lambda }{Dt}
1388  \end{equation*}  \end{equation*}
1389    
1390  \begin{equation*}  \begin{equation*}
1391  v=r\frac{D\phi }{Dt}\qquad  v=r\frac{D\varphi }{Dt}\qquad
1392  \end{equation*}  \end{equation*}
1393  $\qquad \qquad \qquad \qquad $  $\qquad \qquad \qquad \qquad $
1394    
# Line 1413  $\qquad \qquad \qquad \qquad $ Line 1396  $\qquad \qquad \qquad \qquad $
1396  \dot{r}=\frac{Dr}{Dt}  \dot{r}=\frac{Dr}{Dt}
1397  \end{equation*}  \end{equation*}
1398    
1399  Here $\phi $ is the latitude, $\lambda $ the longitude, $r$ the radial  Here $\varphi $ is the latitude, $\lambda $ the longitude, $r$ the radial
1400  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
1401  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.
1402    
# Line 1421  The `grad' ($\nabla $) and `div' ($\nabl Line 1404  The `grad' ($\nabla $) and `div' ($\nabl
1404  spherical coordinates:  spherical coordinates:
1405    
1406  \begin{equation*}  \begin{equation*}
1407  \nabla \equiv \left( \frac{1}{r\cos \phi }\frac{\partial }{\partial \lambda }%  \nabla \equiv \left( \frac{1}{r\cos \varphi }\frac{\partial }{\partial \lambda }
1408  ,\frac{1}{r}\frac{\partial }{\partial \phi },\frac{\partial }{\partial r}%  ,\frac{1}{r}\frac{\partial }{\partial \varphi },\frac{\partial }{\partial r}
1409  \right)  \right)
1410  \end{equation*}  \end{equation*}
1411    
1412  \begin{equation*}  \begin{equation*}
1413  \nabla .v\equiv \frac{1}{r\cos \phi }\left\{ \frac{\partial u}{\partial  \nabla .v\equiv \frac{1}{r\cos \varphi }\left\{ \frac{\partial u}{\partial
1414  \lambda }+\frac{\partial }{\partial \phi }\left( v\cos \phi \right) \right\}  \lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\}
1415  +\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}
1416  \end{equation*}  \end{equation*}
1417    
1418  %%%% \end{document}  %tci%\end{document}

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