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 %%%% \begin{document}  
 %%%%  
 %%%% \tableofcontents  
29    
30  \pagebreak  %tci%\begin{document}
31    
32    %tci%\tableofcontents
33    
 \part{MITgcm basics}  
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 73  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{part1/one_model_figure}
65  \begin{figure}  %% CNHend
 \begin{center}  
 \resizebox{!}{4in}{  
  \rotatebox{90}{  
  \rotatebox{180}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/onemodel.eps}  
  }  
  }  
 }  
 \end{center}  
 \label{fig:onemodel}  
 \end{figure}  
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}
 \marginpar{  
 Fig.2 All scales}\ref{fig:all-scales}  
   
   
 \begin{figure}  
 \begin{center}  
 \resizebox{!}{4in}{  
  \rotatebox{90}{  
  \rotatebox{180}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/scales.eps}  
  }  
  }  
 }  
 \end{center}  
 \label{fig:scales}  
 \end{figure}  
69    
70    %% CNHbegin
71    \input{part1/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{part1/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 130  computational platforms. Line 88  computational platforms.
88  \end{itemize}  \end{itemize}
89    
90  Key publications reporting on and charting the development of the model are  Key publications reporting on and charting the development of the model are
91  listed in an Appendix.  \cite{hill:95,marshall:97a,marshall:97b,adcroft:97,marshall:98,adcroft:99,hill:99,maro-eta:99,adcroft:04a,adcroft:04b,marshall:04}:
92    
93    \begin{verbatim}
94    Hill, C. and J. Marshall, (1995)
95    Application of a Parallel Navier-Stokes Model to Ocean Circulation in
96    Parallel Computational Fluid Dynamics
97    In Proceedings of Parallel Computational Fluid Dynamics: Implementations
98    and Results Using Parallel Computers, 545-552.
99    Elsevier Science B.V.: New York
100    
101    Marshall, J., C. Hill, L. Perelman, and A. Adcroft, (1997)
102    Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling
103    J. Geophysical Res., 102(C3), 5733-5752.
104    
105    Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, (1997)
106    A finite-volume, incompressible Navier Stokes model for studies of the ocean
107    on parallel computers,
108    J. Geophysical Res., 102(C3), 5753-5766.
109    
110    Adcroft, A.J., Hill, C.N. and J. Marshall, (1997)
111    Representation of topography by shaved cells in a height coordinate ocean
112    model
113    Mon Wea Rev, vol 125, 2293-2315
114    
115    Marshall, J., Jones, H. and C. Hill, (1998)
116    Efficient ocean modeling using non-hydrostatic algorithms
117    Journal of Marine Systems, 18, 115-134
118    
119    Adcroft, A., Hill C. and J. Marshall: (1999)
120    A new treatment of the Coriolis terms in C-grid models at both high and low
121    resolutions,
122    Mon. Wea. Rev. Vol 127, pages 1928-1936
123    
124    Hill, C, Adcroft,A., Jamous,D., and J. Marshall, (1999)
125    A Strategy for Terascale Climate Modeling.
126    In Proceedings of the Eighth ECMWF Workshop on the Use of Parallel Processors
127    in Meteorology, pages 406-425
128    World Scientific Publishing Co: UK
129    
130    Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999)
131    Construction of the adjoint MIT ocean general circulation model and
132    application to Atlantic heat transport variability
133    J. Geophysical Res., 104(C12), 29,529-29,547.
134    
135    \end{verbatim}
136    
137  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
138  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  
139    
140  % $Header$  % $Header$
141  % $Name$  % $Name$
142    
143  \section{Illustrations of the model in action}  \section{Illustrations of the model in action}
144    
145  The MITgcm has been designed and used to model a wide range of phenomena,  MITgcm has been designed and used to model a wide range of phenomena,
146  from convection on the scale of meters in the ocean to the global pattern of  from convection on the scale of meters in the ocean to the global pattern of
147  atmospheric winds - see 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
148  kinds of problems the model has been used to study, we briefly describe some  kinds of problems the model has been used to study, we briefly describe some
149  of them here. A more detailed description of the underlying formulation,  of them here. A more detailed description of the underlying formulation,
150  numerical algorithm and implementation that lie behind these calculations is  numerical algorithm and implementation that lie behind these calculations is
151  given later. Indeed it is easy to reproduce the results shown here: simply  given later. Indeed many of the illustrative examples shown below can be
152  download the model (the minimum you need is a PC running linux, together  easily reproduced: simply download the model (the minimum you need is a PC
153  with a FORTRAN\ 77 compiler) and follow the examples.  running Linux, together with a FORTRAN\ 77 compiler) and follow the examples
154    described in detail in the documentation.
155    
156  \subsection{Global atmosphere: `Held-Suarez' benchmark}  \subsection{Global atmosphere: `Held-Suarez' benchmark}
157    \begin{rawhtml}
158    <!-- CMIREDIR:atmospheric_example: -->
159    \end{rawhtml}
160    
 Fig.E1a.\ref{fig:Held-Suarez} is an instaneous plot of the 500$mb$ height  
 field obtained using a 5-level version of the atmospheric pressure isomorph  
 run at 2.8$^{\circ }$ resolution. We see fully developed baroclinic eddies  
 along the northern hemisphere storm track. There are no mountains or  
 land-sea contrast in this calculation, but you can easily put them in. The  
 model is driven by relaxation to a radiative-convective equilibrium profile,  
 following the description set out in Held and Suarez; 1994 designed to test  
 atmospheric hydrodynamical cores - there are no mountains or land-sea  
 contrast. As decribed in Adcroft (2001), a `cubed sphere' is used to  
 descretize the globe permitting a uniform gridding and obviated the need to  
 fourier filter.  
   
 Fig.E1b shows the 5-year mean, zonally averaged potential temperature, zonal  
 wind and meridional overturning streamfunction from the 5-level model.  
   
   
 \begin{figure}  
 \begin{center}  
 \resizebox{!}{4in}{  
  \rotatebox{90}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/hscs.eps}  
  }  
 }  
 \end{center}  
 \label{fig:hscs}  
 \end{figure}  
   
   
 A regular spherical lat-lon grid can also be used.  
   
 \begin{figure}  
 \begin{center}  
 \resizebox{!}{4in}{  
  \rotatebox{90}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/hslatlon.eps}  
  }  
 }  
 \end{center}  
 \label{fig:hslatlon}  
 \end{figure}  
161    
 \subsection{Ocean gyres}  
162    
163  \subsection{Global ocean circulation}  A novel feature of MITgcm is its ability to simulate, using one basic algorithm,
164    both atmospheric and oceanographic flows at both small and large scales.
165  Fig.E2a shows the pattern of ocean currents at the surface of a 4$^{\circ }$  
166  global ocean model run with 15 vertical levels. The model is driven using  Figure \ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$
167  monthly-mean winds with mixed boundary conditions on temperature and  temperature field obtained using the atmospheric isomorph of MITgcm run at
168  salinity at the surface. Fig.E2b shows the overturning (thermohaline)  $2.8^{\circ }$ resolution on the cubed sphere. We see cold air over the pole
169  circulation. Lopped cells are used to represent topography on a regular $%  (blue) and warm air along an equatorial band (red). Fully developed
170  lat-lon$ grid extending from 70$^{\circ }N$ to 70$^{\circ }S$.  baroclinic eddies spawned in the northern hemisphere storm track are
171    evident. There are no mountains or land-sea contrast in this calculation,
172    but you can easily put them in. The model is driven by relaxation to a
173  \begin{figure}  radiative-convective equilibrium profile, following the description set out
174  \begin{center}  in Held and Suarez; 1994 designed to test atmospheric hydrodynamical cores -
175  \resizebox{!}{4in}{  there are no mountains or land-sea contrast.
176  % \rotatebox{90}{  
177    \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/ocean_circ_455_2030.eps}  %% CNHbegin
178  % }  \input{part1/cubic_eddies_figure}
179  }  %% CNHend
180  \end{center}  
181  \label{fig:horizcirc}  As described in Adcroft (2001), a `cubed sphere' is used to discretize the
182  \end{figure}  globe permitting a uniform griding and obviated the need to Fourier filter.
183    The `vector-invariant' form of MITgcm supports any orthogonal curvilinear
184  \begin{figure}  grid, of which the cubed sphere is just one of many choices.
185  \begin{center}  
186  \resizebox{!}{4in}{  Figure \ref{fig:hs_zave_u} shows the 5-year mean, zonally averaged zonal
187   \rotatebox{90}{  wind from a 20-level configuration of
188   \rotatebox{180}{  the model. It compares favorable with more conventional spatial
189    \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/moc.eps}  discretization approaches. The two plots show the field calculated using the
190   }  cube-sphere grid and the flow calculated using a regular, spherical polar
191   }  latitude-longitude grid. Both grids are supported within the model.
192  }  
193  \end{center}  %% CNHbegin
194  \label{fig:moc}  \input{part1/hs_zave_u_figure}
195  \end{figure}  %% CNHend
   
   
 \subsection{Flow over topography}  
   
 \subsection{Ocean convection}  
   
 Fig.E3 shows convection over a slope using the non-hydrostatic ocean  
 isomorph and lopped cells to respresent topography. .....The grid resolution  
 is  
   
 \subsection{Boundary forced internal waves}  
196    
197  \subsection{Carbon outgassing sensitivity}  \subsection{Ocean gyres}
198    \begin{rawhtml}
199    <!-- CMIREDIR:oceanic_example: -->
200    \end{rawhtml}
201    \begin{rawhtml}
202    <!-- CMIREDIR:ocean_gyres: -->
203    \end{rawhtml}
204    
205    Baroclinic instability is a ubiquitous process in the ocean, as well as the
206    atmosphere. Ocean eddies play an important role in modifying the
207    hydrographic structure and current systems of the oceans. Coarse resolution
208    models of the oceans cannot resolve the eddy field and yield rather broad,
209    diffusive patterns of ocean currents. But if the resolution of our models is
210    increased until the baroclinic instability process is resolved, numerical
211    solutions of a different and much more realistic kind, can be obtained.
212    
213    Figure \ref{fig:ocean-gyres} shows the surface temperature and
214    velocity field obtained from MITgcm run at $\frac{1}{6}^{\circ }$
215    horizontal resolution on a \textit{lat-lon} grid in which the pole has
216    been rotated by $90^{\circ }$ on to the equator (to avoid the
217    converging of meridian in northern latitudes). 21 vertical levels are
218    used in the vertical with a `lopped cell' representation of
219    topography. The development and propagation of anomalously warm and
220    cold eddies can be clearly seen in the Gulf Stream region. The
221    transport of warm water northward by the mean flow of the Gulf Stream
222    is also clearly visible.
223    
224    %% CNHbegin
225    \input{part1/atl6_figure}
226    %% CNHend
227    
 Fig.E4 shows....  
228    
229  \begin{figure}  \subsection{Global ocean circulation}
230  \begin{center}  \begin{rawhtml}
231  \resizebox{!}{4in}{  <!-- CMIREDIR:global_ocean_circulation: -->
232    \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/co209.eps}  \end{rawhtml}
233  }  
234  \end{center}  Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean
235  \label{fig:co2mrt}  currents at the surface of a $4^{\circ }$ global ocean model run with
236  \end{figure}  15 vertical levels. Lopped cells are used to represent topography on a
237    regular \textit{lat-lon} grid extending from $70^{\circ }N$ to
238    $70^{\circ }S$. The model is driven using monthly-mean winds with
239    mixed boundary conditions on temperature and salinity at the surface.
240    The transfer properties of ocean eddies, convection and mixing is
241    parameterized in this model.
242    
243    Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning
244    circulation of the global ocean in Sverdrups.
245    
246    %%CNHbegin
247    \input{part1/global_circ_figure}
248    %%CNHend
249    
250    \subsection{Convection and mixing over topography}
251    \begin{rawhtml}
252    <!-- CMIREDIR:mixing_over_topography: -->
253    \end{rawhtml}
254    
255    
256    Dense plumes generated by localized cooling on the continental shelf of the
257    ocean may be influenced by rotation when the deformation radius is smaller
258    than the width of the cooling region. Rather than gravity plumes, the
259    mechanism for moving dense fluid down the shelf is then through geostrophic
260    eddies. The simulation shown in the figure \ref{fig:convect-and-topo}
261    (blue is cold dense fluid, red is
262    warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to
263    trigger convection by surface cooling. The cold, dense water falls down the
264    slope but is deflected along the slope by rotation. It is found that
265    entrainment in the vertical plane is reduced when rotational control is
266    strong, and replaced by lateral entrainment due to the baroclinic
267    instability of the along-slope current.
268    
269    %%CNHbegin
270    \input{part1/convect_and_topo}
271    %%CNHend
272    
273    \subsection{Boundary forced internal waves}
274    \begin{rawhtml}
275    <!-- CMIREDIR:boundary_forced_internal_waves: -->
276    \end{rawhtml}
277    
278    The unique ability of MITgcm to treat non-hydrostatic dynamics in the
279    presence of complex geometry makes it an ideal tool to study internal wave
280    dynamics and mixing in oceanic canyons and ridges driven by large amplitude
281    barotropic tidal currents imposed through open boundary conditions.
282    
283    Fig. \ref{fig:boundary-forced-wave} shows the influence of cross-slope
284    topographic variations on
285    internal wave breaking - the cross-slope velocity is in color, the density
286    contoured. The internal waves are excited by application of open boundary
287    conditions on the left. They propagate to the sloping boundary (represented
288    using MITgcm's finite volume spatial discretization) where they break under
289    nonhydrostatic dynamics.
290    
291    %%CNHbegin
292    \input{part1/boundary_forced_waves}
293    %%CNHend
294    
295    \subsection{Parameter sensitivity using the adjoint of MITgcm}
296    \begin{rawhtml}
297    <!-- CMIREDIR:parameter_sensitivity: -->
298    \end{rawhtml}
299    
300    Forward and tangent linear counterparts of MITgcm are supported using an
301    `automatic adjoint compiler'. These can be used in parameter sensitivity and
302    data assimilation studies.
303    
304    As one example of application of the MITgcm adjoint, Figure
305    \ref{fig:hf-sensitivity} maps the gradient $\frac{\partial J}{\partial
306      \mathcal{H}}$where $J$ is the magnitude of the overturning
307    stream-function shown in figure \ref{fig:large-scale-circ} at
308    $60^{\circ }N$ and $ \mathcal{H}(\lambda,\varphi)$ is the mean, local
309    air-sea heat flux over a 100 year period. We see that $J$ is sensitive
310    to heat fluxes over the Labrador Sea, one of the important sources of
311    deep water for the thermohaline circulations. This calculation also
312    yields sensitivities to all other model parameters.
313    
314    %%CNHbegin
315    \input{part1/adj_hf_ocean_figure}
316    %%CNHend
317    
318    \subsection{Global state estimation of the ocean}
319    \begin{rawhtml}
320    <!-- CMIREDIR:global_state_estimation: -->
321    \end{rawhtml}
322    
323    
324    An important application of MITgcm is in state estimation of the global
325    ocean circulation. An appropriately defined `cost function', which measures
326    the departure of the model from observations (both remotely sensed and
327    in-situ) over an interval of time, is minimized by adjusting `control
328    parameters' such as air-sea fluxes, the wind field, the initial conditions
329    etc. Figure \ref{fig:assimilated-globes} shows the large scale planetary
330    circulation and a Hopf-Muller plot of Equatorial sea-surface height.
331    Both are obtained from assimilation bringing the model in to
332    consistency with altimetric and in-situ observations over the period
333    1992-1997.
334    
335    %% CNHbegin
336    \input{part1/assim_figure}
337    %% CNHend
338    
339    \subsection{Ocean biogeochemical cycles}
340    \begin{rawhtml}
341    <!-- CMIREDIR:ocean_biogeo_cycles: -->
342    \end{rawhtml}
343    
344    MITgcm is being used to study global biogeochemical cycles in the
345    ocean. For example one can study the effects of interannual changes in
346    meteorological forcing and upper ocean circulation on the fluxes of
347    carbon dioxide and oxygen between the ocean and atmosphere. Figure
348    \ref{fig:biogeo} shows the annual air-sea flux of oxygen and its
349    relation to density outcrops in the southern oceans from a single year
350    of a global, interannually varying simulation. The simulation is run
351    at $1^{\circ}\times1^{\circ}$ resolution telescoping to
352    $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not
353    shown).
354    
355    %%CNHbegin
356    \input{part1/biogeo_figure}
357    %%CNHend
358    
359    \subsection{Simulations of laboratory experiments}
360    \begin{rawhtml}
361    <!-- CMIREDIR:classroom_exp: -->
362    \end{rawhtml}
363    
364    Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a
365    laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An
366    initially homogeneous tank of water ($1m$ in diameter) is driven from its
367    free surface by a rotating heated disk. The combined action of mechanical
368    and thermal forcing creates a lens of fluid which becomes baroclinically
369    unstable. The stratification and depth of penetration of the lens is
370    arrested by its instability in a process analogous to that which sets the
371    stratification of the ACC.
372    
373    %%CNHbegin
374    \input{part1/lab_figure}
375    %%CNHend
376    
377  % $Header$  % $Header$
378  % $Name$  % $Name$
379    
380  \section{Continuous equations in `r' coordinates}  \section{Continuous equations in `r' coordinates}
381    \begin{rawhtml}
382    <!-- CMIREDIR:z-p_isomorphism: -->
383    \end{rawhtml}
384    
385  To render atmosphere and ocean models from one dynamical core we exploit  To render atmosphere and ocean models from one dynamical core we exploit
386  `isomorphisms' between equation sets that govern the evolution of the  `isomorphisms' between equation sets that govern the evolution of the
387  respective fluids - see fig.4%  respective fluids - see figure \ref{fig:isomorphic-equations}.
388  \marginpar{  One system of hydrodynamical equations is written down
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down  
389  and encoded. The model variables have different interpretations depending on  and encoded. The model variables have different interpretations depending on
390  whether the atmosphere or ocean is being studied. Thus, for example, the  whether the atmosphere or ocean is being studied. Thus, for example, the
391  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are
392  modeling the atmosphere and height, $z$, if we are modeling the ocean.  modeling the atmosphere (right hand side of figure \ref{fig:isomorphic-equations})
393    and height, $z$, if we are modeling the ocean (left hand side of figure
394    \ref{fig:isomorphic-equations}).
395    
396    %%CNHbegin
397    \input{part1/zandpcoord_figure.tex}
398    %%CNHend
399    
400  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
401  velocity $\vec{\mathbf{v}}$, active tracers $\theta $ and $S$, a  velocity $\vec{\mathbf{v}}$, active tracers $\theta $ and $S$, a
# Line 276  velocity $\vec{\mathbf{v}}$, active trac Line 403  velocity $\vec{\mathbf{v}}$, active trac
403  depend on $\theta $, $S$, and $p$. The equations that govern the evolution  depend on $\theta $, $S$, and $p$. The equations that govern the evolution
404  of these fields, obtained by applying the laws of classical mechanics and  of these fields, obtained by applying the laws of classical mechanics and
405  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of
406  a generic vertical coordinate, $r$, see fig.5%  a generic vertical coordinate, $r$, so that the appropriate
407  \marginpar{  kinematic boundary conditions can be applied isomorphically
408  Fig.5 The vertical coordinate of model}:  see figure \ref{fig:zandp-vert-coord}.
   
 \begin{figure}  
 \begin{center}  
 \resizebox{!}{4in}{  
  \rotatebox{90}{  
  \rotatebox{180}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/vertcoord.eps}  
  }  
  }  
 }  
 \end{center}  
 \label{fig:vertcoord}  
 \end{figure}  
   
 \begin{equation*}  
 \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}%  
 \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}%  
 \text{ horizontal mtm}  
 \end{equation*}  
409    
410  \begin{equation*}  %%CNHbegin
411  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{%  \input{part1/vertcoord_figure.tex}
412    %%CNHend
413    
414    \begin{equation}
415    \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}
416    \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}
417    \text{ horizontal mtm} \label{eq:horizontal_mtm}
418    \end{equation}
419    
420    \begin{equation}
421    \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{
422  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{
423  vertical mtm}  vertical mtm} \label{eq:vertical_mtm}
424  \end{equation*}  \end{equation}
425    
426  \begin{equation}  \begin{equation}
427  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{%  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{
428  \partial r}=0\text{ continuity}  \label{eq:continuous}  \partial r}=0\text{ continuity}  \label{eq:continuity}
429  \end{equation}  \end{equation}
430    
431  \begin{equation*}  \begin{equation}
432  b=b(\theta ,S,r)\text{ equation of state}  b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state}
433  \end{equation*}  \end{equation}
434    
435  \begin{equation*}  \begin{equation}
436  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{  potential temperature}  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}
437  \end{equation*}  \label{eq:potential_temperature}
438    \end{equation}
439    
440  \begin{equation*}  \begin{equation}
441  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{  humidity/salinity}  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}
442  \end{equation*}  \label{eq:humidity_salt}
443    \end{equation}
444    
445  Here:  Here:
446    
447  \begin{equation*}  \begin{equation*}
448  r\text{ is the vertical coordinate}  r\text{ is the vertical coordinate}
449  \end{equation*}  \end{equation*}
450    
451  \begin{equation*}  \begin{equation*}
452  \frac{D}{Dt}=\frac{\partial }{\partial t}+\vec{\mathbf{v}}\cdot \nabla \text{  \frac{D}{Dt}=\frac{\partial }{\partial t}+\vec{\mathbf{v}}\cdot \nabla \text{
453  is the total derivative}  is the total derivative}
454  \end{equation*}  \end{equation*}
455    
456  \begin{equation*}  \begin{equation*}
457  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}%  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}
458  \text{ is the `grad' operator}  \text{ is the `grad' operator}
459  \end{equation*}  \end{equation*}
460  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}%  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}
461  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$
462  is a unit vector in the vertical  is a unit vector in the vertical
463    
464  \begin{equation*}  \begin{equation*}
465  t\text{ is time}  t\text{ is time}
466  \end{equation*}  \end{equation*}
467    
468  \begin{equation*}  \begin{equation*}
469  \vec{\mathbf{v}}=(u,v,\dot{r})=(\vec{\mathbf{v}}_{h},\dot{r})\text{ is the  \vec{\mathbf{v}}=(u,v,\dot{r})=(\vec{\mathbf{v}}_{h},\dot{r})\text{ is the
470  velocity}  velocity}
471  \end{equation*}  \end{equation*}
472    
473  \begin{equation*}  \begin{equation*}
474  \phi \text{ is the `pressure'/`geopotential'}  \phi \text{ is the `pressure'/`geopotential'}
475  \end{equation*}  \end{equation*}
476    
477  \begin{equation*}  \begin{equation*}
478  \vec{\Omega}\text{ is the Earth's rotation}  \vec{\Omega}\text{ is the Earth's rotation}
479  \end{equation*}  \end{equation*}
480    
481  \begin{equation*}  \begin{equation*}
482  b\text{ is the `buoyancy'}  b\text{ is the `buoyancy'}
483  \end{equation*}  \end{equation*}
484    
485  \begin{equation*}  \begin{equation*}
486  \theta \text{ is potential temperature}  \theta \text{ is potential temperature}
487  \end{equation*}  \end{equation*}
488    
489  \begin{equation*}  \begin{equation*}
490  S\text{ is specific humidity in the atmosphere; salinity in the ocean}  S\text{ is specific humidity in the atmosphere; salinity in the ocean}
491  \end{equation*}  \end{equation*}
492    
493  \begin{equation*}  \begin{equation*}
494  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{%  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{
495  \mathbf{v}}  \mathbf{v}}
496  \end{equation*}  \end{equation*}
497    
498  \begin{equation*}  \begin{equation*}
499  \mathcal{Q}_{\theta }\mathcal{\ }\text{are forcing and dissipation of }%  \mathcal{Q}_{\theta }\mathcal{\ }\text{are forcing and dissipation of }\theta
 \theta  
500  \end{equation*}  \end{equation*}
501    
502  \begin{equation*}  \begin{equation*}
# Line 385  S\text{ is specific humidity in the atmo Line 504  S\text{ is specific humidity in the atmo
504  \end{equation*}  \end{equation*}
505    
506  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
507  extensive `physics' packages for atmosphere and ocean described in Chapter 6.  `physics' and forcing packages for atmosphere and ocean. These are described
508    in later chapters.
509    
510  \subsection{Kinematic Boundary conditions}  \subsection{Kinematic Boundary conditions}
511    
512  \subsubsection{vertical}  \subsubsection{vertical}
513    
514  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}):
515    
516  \begin{equation}  \begin{equation}
517  \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)}
518  \label{eq:fixedbc}  \label{eq:fixedbc}
519  \end{equation}  \end{equation}
520    
521  \begin{equation}  \begin{equation}
522  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \  \dot{r}=\frac{Dr}{Dt} \text{\ at\ } r=R_{moving}\text{ \
523  (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc}  (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc}
524  \end{equation}  \end{equation}
525    
526  Here  Here
527    
528  \begin{equation*}  \begin{equation*}
529  R_{moving}=R_{o}+\eta  R_{moving}=R_{o}+\eta
530  \end{equation*}  \end{equation*}
531  where $R_{o}(x,y)$ is the `$r-$value' (height or pressure, depending on  where $R_{o}(x,y)$ is the `$r-$value' (height or pressure, depending on
532  whether we are in the atmosphere or ocean) of the `moving surface' in the  whether we are in the atmosphere or ocean) of the `moving surface' in the
# Line 417  of motion. Line 537  of motion.
537    
538  \begin{equation}  \begin{equation}
539  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}
540  \end{equation}%  \end{equation}
541  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.
542    
543  \subsection{Atmosphere}  \subsection{Atmosphere}
544    
545  In the atmosphere, see fig.5, we interpret:  In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret:
546    
547  \begin{equation}  \begin{equation}
548  r=p\text{ is the pressure}  \label{eq:atmos-r}  r=p\text{ is the pressure}  \label{eq:atmos-r}
# Line 454  where Line 574  where
574    
575  \begin{equation*}  \begin{equation*}
576  T\text{ is absolute temperature}  T\text{ is absolute temperature}
577  \end{equation*}%  \end{equation*}
578  \begin{equation*}  \begin{equation*}
579  p\text{ is the pressure}  p\text{ is the pressure}
580  \end{equation*}%  \end{equation*}
581  \begin{eqnarray*}  \begin{eqnarray*}
582  &&z\text{ is the height of the pressure surface} \\  &&z\text{ is the height of the pressure surface} \\
583  &&g\text{ is the acceleration due to gravity}  &&g\text{ is the acceleration due to gravity}
# Line 467  In the above the ideal gas law, $p=\rho Line 587  In the above the ideal gas law, $p=\rho
587  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)
588  \begin{equation}  \begin{equation}
589  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}
590  \end{equation}%  \end{equation}
591  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
592  constant and $c_{p}$ the specific heat of air at constant pressure.  constant and $c_{p}$ the specific heat of air at constant pressure.
593    
594  At the top of the atmosphere (which is `fixed' in our $r$ coordinate):  At the top of the atmosphere (which is `fixed' in our $r$ coordinate):
595    
596  \begin{equation*}  \begin{equation*}
597  R_{fixed}=p_{top}=0  R_{fixed}=p_{top}=0
598  \end{equation*}  \end{equation*}
599  In a resting atmosphere the elevation of the mountains at the bottom is  In a resting atmosphere the elevation of the mountains at the bottom is
600  given by  given by
601  \begin{equation*}  \begin{equation*}
602  R_{moving}=R_{o}(x,y)=p_{o}(x,y)  R_{moving}=R_{o}(x,y)=p_{o}(x,y)
603  \end{equation*}  \end{equation*}
604  i.e. the (hydrostatic) pressure at the top of the mountains in a resting  i.e. the (hydrostatic) pressure at the top of the mountains in a resting
605  atmosphere.  atmosphere.
# Line 493  The boundary conditions at top and botto Line 613  The boundary conditions at top and botto
613  atmosphere)}  \label{eq:moving-bc-atmos}  atmosphere)}  \label{eq:moving-bc-atmos}
614  \end{eqnarray}  \end{eqnarray}
615    
616  Then the (hydrostatic form of) eq(\ref{eq:continuous}) yields a consistent  Then the (hydrostatic form of) equations
617  set of atmospheric equations which, for convenience, are written out in $p$  (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt}) yields a consistent
618  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).  set of atmospheric equations which, for convenience, are written out
619    in $p$ coordinates in Appendix Atmosphere - see
620    eqs(\ref{eq:atmos-prime}).
621    
622  \subsection{Ocean}  \subsection{Ocean}
623    
# Line 517  At the bottom of the ocean: $R_{fixed}(x Line 639  At the bottom of the ocean: $R_{fixed}(x
639    
640  The surface of the ocean is given by: $R_{moving}=\eta $  The surface of the ocean is given by: $R_{moving}=\eta $
641    
642  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 $
643  R_{o}=Z_{o}=0$.  R_{o}=Z_{o}=0$.
644    
645  Boundary conditions are:  Boundary conditions are:
# Line 525  Boundary conditions are: Line 647  Boundary conditions are:
647  \begin{eqnarray}  \begin{eqnarray}
648  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}
649  \\  \\
650  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)
651  \label{eq:moving-bc-ocean}}  \label{eq:moving-bc-ocean}}
652  \end{eqnarray}  \end{eqnarray}
653  where $\eta $ is the elevation of the free surface.  where $\eta $ is the elevation of the free surface.
654    
655  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
656    of oceanic equations
657  which, for convenience, are written out in $z$ coordinates in Appendix Ocean  which, for convenience, are written out in $z$ coordinates in Appendix Ocean
658  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).
659    
660  \subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and  \subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and
661  Non-hydrostatic forms}  Non-hydrostatic forms}
662    \begin{rawhtml}
663    <!-- CMIREDIR:non_hydrostatic: -->
664    \end{rawhtml}
665    
666    
667  Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms:  Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms:
668    
669  \begin{equation}  \begin{equation}
670  \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)
671  \label{eq:phi-split}  \label{eq:phi-split}
672  \end{equation}%  \end{equation}
673  and write eq(\ref{incompressible}a,b) in the form:  %and write eq(\ref{eq:incompressible}) in the form:
674    %                  ^- this eq is missing (jmc) ; replaced with:
675    and write eq( \ref{eq:horizontal_mtm}) in the form:
676    
677  \begin{equation}  \begin{equation}
678  \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 556  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l Line 685  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l
685  \end{equation}  \end{equation}
686    
687  \begin{equation}  \begin{equation}
688  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{%  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{
689  \partial r}=G_{\dot{r}}  \label{eq:mom-w}  \partial r}=G_{\dot{r}}  \label{eq:mom-w}
690  \end{equation}  \end{equation}
691  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.
692    
693  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
694  {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
695  terms in the momentum equations. In spherical coordinates they take the form%  terms in the momentum equations. In spherical coordinates they take the form
696  \footnote{%  \footnote{
697  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms
698  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref%  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref
699  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in
700  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (%  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (
701  \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
702  discussion:  discussion:
703    
# Line 576  discussion: Line 705  discussion:
705  \left.  \left.
706  \begin{tabular}{l}  \begin{tabular}{l}
707  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\
708  $-\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\} $
709  \\  \\
710  $-\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\} $
711  \\  \\
712  $+\mathcal{F}_{u}$%  $+\mathcal{F}_{u}$
713  \end{tabular}%  \end{tabular}
714  \ \right\} \left\{  \ \right\} \left\{
715  \begin{tabular}{l}  \begin{tabular}{l}
716  \textit{advection} \\  \textit{advection} \\
717  \textit{metric} \\  \textit{metric} \\
718  \textit{Coriolis} \\  \textit{Coriolis} \\
719  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
720  \end{tabular}%  \end{tabular}
721  \ \right. \qquad   \label{eq:gu-speherical}  \ \right. \qquad  \label{eq:gu-speherical}
722  \end{equation}  \end{equation}
723    
724  \begin{equation}  \begin{equation}
725  \left.  \left.
726  \begin{tabular}{l}  \begin{tabular}{l}
727  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\
728  $-\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\}
729  $ \\  $ \\
730  $-\left\{ -2\Omega u\sin lat\right\} $ \\  $-\left\{ -2\Omega u\sin \varphi \right\} $ \\
731  $+\mathcal{F}_{v}$%  $+\mathcal{F}_{v}$
732  \end{tabular}%  \end{tabular}
733  \ \right\} \left\{  \ \right\} \left\{
734  \begin{tabular}{l}  \begin{tabular}{l}
735  \textit{advection} \\  \textit{advection} \\
736  \textit{metric} \\  \textit{metric} \\
737  \textit{Coriolis} \\  \textit{Coriolis} \\
738  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
739  \end{tabular}%  \end{tabular}
740  \ \right. \qquad   \label{eq:gv-spherical}  \ \right. \qquad  \label{eq:gv-spherical}
741  \end{equation}%  \end{equation}
742  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
743    
744  \begin{equation}  \begin{equation}
745  \left.  \left.
746  \begin{tabular}{l}  \begin{tabular}{l}
747  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\
748  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\
749  ${+}\underline{{2\Omega u\cos lat}}$ \\  ${+}\underline{{2\Omega u\cos \varphi}}$ \\
750  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$%  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$
751  \end{tabular}%  \end{tabular}
752  \ \right\} \left\{  \ \right\} \left\{
753  \begin{tabular}{l}  \begin{tabular}{l}
754  \textit{advection} \\  \textit{advection} \\
755  \textit{metric} \\  \textit{metric} \\
756  \textit{Coriolis} \\  \textit{Coriolis} \\
757  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
758  \end{tabular}%  \end{tabular}
759  \ \right.   \label{eq:gw-spherical}  \ \right.  \label{eq:gw-spherical}
760  \end{equation}%  \end{equation}
761  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
762    
763  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 `$\varphi$
764  ' is latitude.  ' is latitude.
765    
766  Grad and div operators in spherical coordinates are defined in appendix  Grad and div operators in spherical coordinates are defined in appendix
767  OPERATORS.%  OPERATORS.
 \marginpar{  
 Fig.6 Spherical polar coordinate system.}  
   
 \begin{figure}  
 \begin{center}  
 \resizebox{!}{4in}{  
  \rotatebox{90}{  
  \rotatebox{180}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/spherical-polar.eps}  
  }  
  }  
 }  
 \end{center}  
 \label{fig:spcoord}  
 \end{figure}  
768    
769    %%CNHbegin
770    \input{part1/sphere_coord_figure.tex}
771    %%CNHend
772    
773  \subsubsection{Shallow atmosphere approximation}  \subsubsection{Shallow atmosphere approximation}
774    
775  Most models are based on the `hydrostatic primitive equations' (HPE's) in  Most models are based on the `hydrostatic primitive equations' (HPE's)
776  which the vertical momentum equation is reduced to a statement of  in which the vertical momentum equation is reduced to a statement of
777  hydrostatic balance and the `traditional approximation' is made in which the  hydrostatic balance and the `traditional approximation' is made in
778  Coriolis force is treated approximately and the shallow atmosphere  which the Coriolis force is treated approximately and the shallow
779  approximation is made.\ The MITgcm need not make the `traditional  atmosphere approximation is made.  MITgcm need not make the
780  approximation'. To be able to support consistent non-hydrostatic forms the  `traditional approximation'. To be able to support consistent
781  shallow atmosphere approximation can be relaxed - when dividing through by $r  non-hydrostatic forms the shallow atmosphere approximation can be
782  $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$,  relaxed - when dividing through by $ r $ in, for example,
783  the radius of the earth.  (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, the radius of
784    the earth.
785    
786  \subsubsection{Hydrostatic and quasi-hydrostatic forms}  \subsubsection{Hydrostatic and quasi-hydrostatic forms}
787    \label{sec:hydrostatic_and_quasi-hydrostatic_forms}
788    
789  These are discussed at length in Marshall et al (1997a).  These are discussed at length in Marshall et al (1997a).
790    
# Line 674  terms in Eqs. (\ref{eq:gu-speherical} $\ Line 793  terms in Eqs. (\ref{eq:gu-speherical} $\
793  are neglected and `${r}$' is replaced by `$a$', the mean radius of the  are neglected and `${r}$' is replaced by `$a$', the mean radius of the
794  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
795  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
796  computed at all other levels by integration of the hydrostatic relation, eq(%  computed at all other levels by integration of the hydrostatic relation, eq(
797  \ref{eq:hydrostatic}).  \ref{eq:hydrostatic}).
798    
799  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between
800  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
801  \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
802  contribution to the pressure field: only the terms underlined twice in Eqs. (%  contribution to the pressure field: only the terms underlined twice in Eqs. (
803  \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
804  and, simultaneously, the shallow atmosphere approximation is relaxed. In  and, simultaneously, the shallow atmosphere approximation is relaxed. In
805  \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 688  variation of the radial position of a pa Line 807  variation of the radial position of a pa
807  vertical momentum equation (\ref{eq:mom-w}) becomes:  vertical momentum equation (\ref{eq:mom-w}) becomes:
808    
809  \begin{equation*}  \begin{equation*}
810  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos lat  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos \varphi
811  \end{equation*}  \end{equation*}
812  making a small correction to the hydrostatic pressure.  making a small correction to the hydrostatic pressure.
813    
# Line 699  et.al., 1997a. As in \textbf{HPE }only a Line 818  et.al., 1997a. As in \textbf{HPE }only a
818    
819  \subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms}  \subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms}
820    
821  The MIT model presently supports a full non-hydrostatic ocean isomorph, but  MITgcm presently supports a full non-hydrostatic ocean isomorph, but
822  only a quasi-non-hydrostatic atmospheric isomorph.  only a quasi-non-hydrostatic atmospheric isomorph.
823    
824  \paragraph{Non-hydrostatic Ocean}  \paragraph{Non-hydrostatic Ocean}
825    
826  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref%  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref
827  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A
828  three dimensional elliptic equation must be solved subject to Neumann  three dimensional elliptic equation must be solved subject to Neumann
829  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
830  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
831  incompressible condition eq(\ref{eq:continuous})c has already filtered out  incompressible condition eq(\ref{eq:continuity}) has already filtered out
832  acoustic modes. It does, however, ensure that the gravity waves are treated  acoustic modes. It does, however, ensure that the gravity waves are treated
833  accurately with an exact dispersion relation. The \textbf{NH} set has a  accurately with an exact dispersion relation. The \textbf{NH} set has a
834  complete angular momentum principle and consistent energetics - see White  complete angular momentum principle and consistent energetics - see White
# Line 717  and Bromley, 1995; Marshall et.al.\ 1997 Line 836  and Bromley, 1995; Marshall et.al.\ 1997
836    
837  \paragraph{Quasi-nonhydrostatic Atmosphere}  \paragraph{Quasi-nonhydrostatic Atmosphere}
838    
839  In the non-hydrostatic version of our atmospheric model we approximate $\dot{%  In the non-hydrostatic version of our atmospheric model we approximate $\dot{
840  r}$ 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})
841  (but only here) by:  (but only here) by:
842    
843  \begin{equation}  \begin{equation}
844  \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}
845  \end{equation}%  \end{equation}
846  where $p_{hy}$ is the hydrostatic pressure.  where $p_{hy}$ is the hydrostatic pressure.
847    
848  \subsubsection{Summary of equation sets supported by model}  \subsubsection{Summary of equation sets supported by model}
# Line 751  equations in $z-$coordinates are support Line 870  equations in $z-$coordinates are support
870    
871  \subparagraph{Non-hydrostatic}  \subparagraph{Non-hydrostatic}
872    
873  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$%  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$
874  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref%  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref
875  {eq:ocean-salt}).  {eq:ocean-salt}).
876    
877  \subsection{Solution strategy}  \subsection{Solution strategy}
878    
879  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{
880  NH} models is summarized in Fig.7.%  NH} models is summarized in Figure \ref{fig:solution-strategy}.
881  \marginpar{  Under all dynamics, a 2-d elliptic equation is
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is  
882  first solved to find the surface pressure and the hydrostatic pressure at  first solved to find the surface pressure and the hydrostatic pressure at
883  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
884  \textbf{QH} dynamics, the horizontal momentum equations are then stepped  \textbf{QH} dynamics, the horizontal momentum equations are then stepped
# Line 769  forward and $\dot{r}$ found from continu Line 887  forward and $\dot{r}$ found from continu
887  stepping forward the horizontal momentum equations; $\dot{r}$ is found by  stepping forward the horizontal momentum equations; $\dot{r}$ is found by
888  stepping forward the vertical momentum equation.  stepping forward the vertical momentum equation.
889    
890  \begin{figure}  %%CNHbegin
891  \begin{center}  \input{part1/solution_strategy_figure.tex}
892  \resizebox{!}{4in}{  %%CNHend
  \rotatebox{90}{  
  \rotatebox{180}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/soln_strategy.eps}  
  }  
  }  
 }  
 \end{center}  
 \label{fig:solnstart}  
 \end{figure}  
   
893    
894  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
895  course, some complication that goes with the inclusion of $\cos \phi \ $%  course, some complication that goes with the inclusion of $\cos \varphi \ $
896  Coriolis terms and the relaxation of the shallow atmosphere approximation.  Coriolis terms and the relaxation of the shallow atmosphere approximation.
897  But this leads to negligible increase in computation. In \textbf{NH}, in  But this leads to negligible increase in computation. In \textbf{NH}, in
898  contrast, one additional elliptic equation - a three-dimensional one - must  contrast, one additional elliptic equation - a three-dimensional one - must
# Line 794  Marshall et al, 1997) resulting in a non Line 902  Marshall et al, 1997) resulting in a non
902  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.
903    
904  \subsection{Finding the pressure field}  \subsection{Finding the pressure field}
905    \label{sec:finding_the_pressure_field}
906    
907  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the
908  pressure field must be obtained diagnostically. We proceed, as before, by  pressure field must be obtained diagnostically. We proceed, as before, by
# Line 808  Hydrostatic pressure is obtained by inte Line 917  Hydrostatic pressure is obtained by inte
917  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:
918    
919  \begin{equation*}  \begin{equation*}
920  \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}
921  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr
922  \end{equation*}  \end{equation*}
923  and so  and so
924    
# Line 826  atmospheric pressure pushing down on the Line 935  atmospheric pressure pushing down on the
935    
936  \subsubsection{Surface pressure}  \subsubsection{Surface pressure}
937    
938  The surface pressure equation can be obtained by integrating continuity, (%  The surface pressure equation can be obtained by integrating continuity,
939  \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$  (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$
940    
941  \begin{equation*}  \begin{equation*}
942  \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}
943  }_{h}+\partial _{r}\dot{r}\right) dr=0  }_{h}+\partial _{r}\dot{r}\right) dr=0
944  \end{equation*}  \end{equation*}
945    
946  Thus:  Thus:
947    
948  \begin{equation*}  \begin{equation*}
949  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta
950  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}%  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}
951  _{h}dr=0  _{h}dr=0
952  \end{equation*}  \end{equation*}
953  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 $
954  r $. The above can be rearranged to yield, using Leibnitz's theorem:  r $. The above can be rearranged to yield, using Leibnitz's theorem:
955    
956  \begin{equation}  \begin{equation}
957  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot
958  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}
959  \label{eq:free-surface}  \label{eq:free-surface}
960  \end{equation}%  \end{equation}
961  where we have incorporated a source term.  where we have incorporated a source term.
962    
963  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential
964  (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can  (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can
965  be written  be written
966  \begin{equation}  \begin{equation}
967  \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)
968  \label{eq:phi-surf}  \label{eq:phi-surf}
969  \end{equation}%  \end{equation}
970  where $b_{s}$ is the buoyancy at the surface.  where $b_{s}$ is the buoyancy at the surface.
971    
972  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
973  {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
974  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free
975  surface' and `rigid lid' approaches are available.  surface' and `rigid lid' approaches are available.
976    
977  \subsubsection{Non-hydrostatic pressure}  \subsubsection{Non-hydrostatic pressure}
978    
979  Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{%  Taking the horizontal divergence of (\ref{eq:mom-h}) and adding
980  \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation  $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation
981  (\ref{incompressible}), we deduce that:  (\ref{eq:continuity}), we deduce that:
982    
983  \begin{equation}  \begin{equation}
984  \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{
985  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .%  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .
986  \vec{\mathbf{F}}  \label{eq:3d-invert}  \vec{\mathbf{F}}  \label{eq:3d-invert}
987  \end{equation}  \end{equation}
988    
# Line 893  coasts (in the ocean) and the bottom: Line 1002  coasts (in the ocean) and the bottom:
1002  \end{equation}  \end{equation}
1003  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
1004  kinematic condition (\ref{nonormalflow}) is also applied to the vertical  kinematic condition (\ref{nonormalflow}) is also applied to the vertical
1005  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 $
1006  \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
1007  tangential component of velocity, $v_{T}$, at all solid boundaries,  tangential component of velocity, $v_{T}$, at all solid boundaries,
1008  depending on the form chosen for the dissipative terms in the momentum  depending on the form chosen for the dissipative terms in the momentum
1009  equations - see below.  equations - see below.
1010    
1011  Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that:  Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that:
1012    
1013  \begin{equation}  \begin{equation}
1014  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}
# Line 910  where Line 1019  where
1019  \begin{equation*}  \begin{equation*}
1020  \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
1021  _{s}+\mathbf{\nabla }\phi _{hyd}\right)  _{s}+\mathbf{\nabla }\phi _{hyd}\right)
1022  \end{equation*}%  \end{equation*}
1023  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem
1024  (\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
1025  exploit classical 3D potential theory and, by introducing an appropriately  exploit classical 3D potential theory and, by introducing an appropriately
1026  chosen $\delta $-function sheet of `source-charge', replace the inhomogenous  chosen $\delta $-function sheet of `source-charge', replace the
1027  boundary condition on pressure by a homogeneous one. The source term $rhs$  inhomogeneous boundary condition on pressure by a homogeneous one. The
1028  in (\ref{eq:3d-invert}) is the divergence of the vector $\vec{\mathbf{F}}.$  source term $rhs$ in (\ref{eq:3d-invert}) is the divergence of the vector $
1029  By simultaneously setting $%  \vec{\mathbf{F}}.$ By simultaneously setting $
1030  \begin{array}{l}  \begin{array}{l}
1031  \widehat{n}.\vec{\mathbf{F}}%  \widehat{n}.\vec{\mathbf{F}}
1032  \end{array}%  \end{array}
1033  =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
1034  self-consistent but simpler homogenised Elliptic problem is obtained:  self-consistent but simpler homogenized Elliptic problem is obtained:
1035    
1036  \begin{equation*}  \begin{equation*}
1037  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad
1038  \end{equation*}%  \end{equation*}
1039  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such
1040  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
1041  {eq:inhom-neumann-nh}) the modified boundary condition becomes:  {eq:inhom-neumann-nh}) the modified boundary condition becomes:
1042    
1043  \begin{equation}  \begin{equation}
# Line 939  If the flow is `close' to hydrostatic ba Line 1048  If the flow is `close' to hydrostatic ba
1048  converges rapidly because $\phi _{nh}\ $is then only a small correction to  converges rapidly because $\phi _{nh}\ $is then only a small correction to
1049  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).
1050    
1051  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})
1052  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.
1053    
1054  \subsection{Forcing/dissipation}  \subsection{Forcing/dissipation}
# Line 947  does not vanish at $r=R_{moving}$, and s Line 1056  does not vanish at $r=R_{moving}$, and s
1056  \subsubsection{Forcing}  \subsubsection{Forcing}
1057    
1058  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
1059  `physics packages' described in detail in chapter ??.  `physics packages' and forcing packages. These are described later on.
1060    
1061  \subsubsection{Dissipation}  \subsubsection{Dissipation}
1062    
# Line 957  Many forms of momentum dissipation are a Line 1066  Many forms of momentum dissipation are a
1066  biharmonic frictions are commonly used:  biharmonic frictions are commonly used:
1067    
1068  \begin{equation}  \begin{equation}
1069  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}}
1070  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}
1071  \end{equation}  \end{equation}
1072  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 968  friction. These coefficients are the sam Line 1077  friction. These coefficients are the sam
1077    
1078  The mixing terms for the temperature and salinity equations have a similar  The mixing terms for the temperature and salinity equations have a similar
1079  form to that of momentum except that the diffusion tensor can be  form to that of momentum except that the diffusion tensor can be
1080  non-diagonal and have varying coefficients. $\qquad $%  non-diagonal and have varying coefficients. $\qquad $
1081  \begin{equation}  \begin{equation}
1082  D_{T,S}=\nabla .[\underline{\underline{K}}\nabla (T,S)]+K_{4}\nabla  D_{T,S}=\nabla .[\underline{\underline{K}}\nabla (T,S)]+K_{4}\nabla
1083  _{h}^{4}(T,S)  \label{eq:diffusion}  _{h}^{4}(T,S)  \label{eq:diffusion}
1084  \end{equation}  \end{equation}
1085  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $%  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $
1086  horizontal coefficient for biharmonic diffusion. In the simplest case where  horizontal coefficient for biharmonic diffusion. In the simplest case where
1087  the subgrid-scale fluxes of heat and salt are parameterized with constant  the subgrid-scale fluxes of heat and salt are parameterized with constant
1088  horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$,  horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$,
# Line 984  reduces to a diagonal matrix with consta Line 1093  reduces to a diagonal matrix with consta
1093  \begin{array}{ccc}  \begin{array}{ccc}
1094  K_{h} & 0 & 0 \\  K_{h} & 0 & 0 \\
1095  0 & K_{h} & 0 \\  0 & K_{h} & 0 \\
1096  0 & 0 & K_{v}%  0 & 0 & K_{v}
1097  \end{array}  \end{array}
1098  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}
1099  \end{equation}  \end{equation}
# Line 994  salinity ... ). Line 1103  salinity ... ).
1103    
1104  \subsection{Vector invariant form}  \subsection{Vector invariant form}
1105    
1106  For some purposes it is advantageous to write momentum advection in eq(\ref%  For some purposes it is advantageous to write momentum advection in
1107  {hor-mtm}) and (\ref{vertmtm}) in the (so-called) `vector invariant' form:  eq(\ref {eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the
1108    (so-called) `vector invariant' form:
1109    
1110  \begin{equation}  \begin{equation}
1111  \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}
1112  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla %  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla
1113  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]
1114  \label{eq:vi-identity}  \label{eq:vi-identity}
1115  \end{equation}%  \end{equation}
1116  This permits alternative numerical treatments of the non-linear terms based  This permits alternative numerical treatments of the non-linear terms based
1117  on their representation as a vorticity flux. Because gradients of coordinate  on their representation as a vorticity flux. Because gradients of coordinate
1118  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
1119  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref%  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref
1120  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information
1121  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
1122  to discretize the model.  to discretize the model.
1123    
1124  \subsection{Adjoint}  \subsection{Adjoint}
1125    
1126  Tangent linear and adoint counterparts of the forward model and described in  Tangent linear and adjoint counterparts of the forward model are described
1127  Chapter 5.  in Chapter 5.
1128    
1129  % $Header$  % $Header$
1130  % $Name$  % $Name$
# Line 1028  coordinates} Line 1138  coordinates}
1138    
1139  The hydrostatic primitive equations (HPEs) in p-coordinates are:  The hydrostatic primitive equations (HPEs) in p-coordinates are:
1140  \begin{eqnarray}  \begin{eqnarray}
1141  \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}}
1142  _{h}+\mathbf{\nabla }_{p}\phi  &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}
1143  \label{eq:atmos-mom} \\  \label{eq:atmos-mom} \\
1144  \frac{\partial \phi }{\partial p}+\alpha  &=&0  \label{eq-p-hydro-start} \\  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\
1145  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1146  \partial p} &=&0  \label{eq:atmos-cont} \\  \partial p} &=&0  \label{eq:atmos-cont} \\
1147  p\alpha  &=&RT  \label{eq:atmos-eos} \\  p\alpha &=&RT  \label{eq:atmos-eos} \\
1148  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}
1149  \end{eqnarray}%  \end{eqnarray}
1150  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
1151  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot
1152  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total
1153  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
1154  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp%  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp
1155  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref%  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref
1156  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $%  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $
1157  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 $
1158  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.
1159    
1160  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 1052  $\theta $ so that it looks more like a g Line 1162  $\theta $ so that it looks more like a g
1162  Differentiating (\ref{eq:atmos-eos}) we get:  Differentiating (\ref{eq:atmos-eos}) we get:
1163  \begin{equation*}  \begin{equation*}
1164  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}
1165  \end{equation*}%  \end{equation*}
1166  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 $
1167  c_{p}=c_{v}+R$, gives:  c_{p}=c_{v}+R$, gives:
1168  \begin{equation}  \begin{equation}
1169  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}
1170  \label{eq-p-heat-interim}  \label{eq-p-heat-interim}
1171  \end{equation}%  \end{equation}
1172  Potential temperature is defined:  Potential temperature is defined:
1173  \begin{equation}  \begin{equation}
1174  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}
1175  \end{equation}%  \end{equation}
1176  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
1177  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:
1178  \begin{equation}  \begin{equation}
1179  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}
1180  \end{equation}%  \end{equation}
1181  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
1182  the Exner function:  the Exner function:
1183  \begin{equation*}  \begin{equation*}
1184  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
1185  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{%  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{
1186  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}%  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}
1187  \frac{Dp}{Dt}  \frac{Dp}{Dt}
1188  \end{equation*}%  \end{equation*}
1189  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.
1190    
1191  The heat equation is obtained by noting that  The heat equation is obtained by noting that
1192  \begin{equation*}  \begin{equation*}
1193  c_{p}\frac{DT}{Dt}=\frac{D(\Pi \theta )}{Dt}=\Pi \frac{D\theta }{Dt}+\theta  c_{p}\frac{DT}{Dt}=\frac{D(\Pi \theta )}{Dt}=\Pi \frac{D\theta }{Dt}+\theta
1194  \frac{D\Pi }{Dt}=\Pi \frac{D\theta }{Dt}+\alpha \frac{Dp}{Dt}  \frac{D\Pi }{Dt}=\Pi \frac{D\theta }{Dt}+\alpha \frac{Dp}{Dt}
1195  \end{equation*}  \end{equation*}
1196  and on substituting into (\ref{eq-p-heat-interim}) gives:  and on substituting into (\ref{eq-p-heat-interim}) gives:
1197  \begin{equation}  \begin{equation}
# Line 1090  and on substituting into (\ref{eq-p-heat Line 1200  and on substituting into (\ref{eq-p-heat
1200  \end{equation}  \end{equation}
1201  which is in conservative form.  which is in conservative form.
1202    
1203  For convenience in the model we prefer to step forward (\ref%  For convenience in the model we prefer to step forward (\ref
1204  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).
1205    
1206  \subsubsection{Boundary conditions}  \subsubsection{Boundary conditions}
# Line 1106  In $p$-coordinates, the upper boundary a Line 1216  In $p$-coordinates, the upper boundary a
1216  surface ($\phi $ is imposed and $\omega \neq 0$).  surface ($\phi $ is imposed and $\omega \neq 0$).
1217    
1218  \subsubsection{Splitting the geo-potential}  \subsubsection{Splitting the geo-potential}
1219    \label{sec:hpe-p-geo-potential-split}
1220    
1221  For the purposes of initialization and reducing round-off errors, the model  For the purposes of initialization and reducing round-off errors, the model
1222  deals with perturbations from reference (or ``standard'') profiles. For  deals with perturbations from reference (or ``standard'') profiles. For
# Line 1134  _{o}(p_{o})=g~Z_{topo}$, defined: Line 1245  _{o}(p_{o})=g~Z_{topo}$, defined:
1245    
1246  The final form of the HPE's in p coordinates is then:  The final form of the HPE's in p coordinates is then:
1247  \begin{eqnarray}  \begin{eqnarray}
1248  \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}}
1249  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}}
1250    \label{eq:atmos-prime} \\
1251  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\
1252  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1253  \partial p} &=&0 \\  \partial p} &=&0 \\
1254  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\
1255  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime}  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }
1256  \end{eqnarray}  \end{eqnarray}
1257    
1258  % $Header$  % $Header$
# Line 1154  We review here the method by which the s Line 1266  We review here the method by which the s
1266  HPE's for the ocean written in z-coordinates are obtained. The  HPE's for the ocean written in z-coordinates are obtained. The
1267  non-Boussinesq equations for oceanic motion are:  non-Boussinesq equations for oceanic motion are:
1268  \begin{eqnarray}  \begin{eqnarray}
1269  \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}}
1270  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\
1271  \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}
1272  &=&\epsilon _{nh}\mathcal{F}_{w} \\  &=&\epsilon _{nh}\mathcal{F}_{w} \\
1273  \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}}
1274  _{h}+\frac{\partial w}{\partial z} &=&0 \\  _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\
1275  \rho  &=&\rho (\theta ,S,p) \\  \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\
1276  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\
1277  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt}
1278  \end{eqnarray}%  \label{eq:non-boussinesq}
1279    \end{eqnarray}
1280  These equations permit acoustics modes, inertia-gravity waves,  These equations permit acoustics modes, inertia-gravity waves,
1281  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline
1282  mode. As written, they cannot be integrated forward consistently - if we  mode. As written, they cannot be integrated forward consistently - if we
1283  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
1284  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref%  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref
1285  {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
1286  therefore necessary to manipulate the system as follows. Differentiating the  therefore necessary to manipulate the system as follows. Differentiating the
1287  EOS (equation of state) gives:  EOS (equation of state) gives:
# Line 1180  _{\theta ,p}\frac{DS}{Dt}+\left. \frac{\ Line 1293  _{\theta ,p}\frac{DS}{Dt}+\left. \frac{\
1293  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexpansion}  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexpansion}
1294  \end{equation}  \end{equation}
1295    
1296  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
1297  reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref%  the reciprocal of the sound speed ($c_{s}$) squared. Substituting into
1298  {eq-zns-cont} gives:  \ref{eq-zns-cont} gives:
1299  \begin{equation}  \begin{equation}
1300  \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{
1301  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}
1302  \end{equation}  \end{equation}
1303  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 1192  adiabatic motion, dropping the $\frac{D\ Line 1305  adiabatic motion, dropping the $\frac{D\
1305  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
1306  can be explicitly integrated forward:  can be explicitly integrated forward:
1307  \begin{eqnarray}  \begin{eqnarray}
1308  \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}}
1309  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1310  \label{eq-cns-hmom} \\  \label{eq-cns-hmom} \\
1311  \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}
1312  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\
1313  \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{
1314  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\
1315  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\
1316  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\
# Line 1211  wherever it appears in a product (ie. no Line 1324  wherever it appears in a product (ie. no
1324  `Boussinesq assumption'. The only term that then retains the full variation  `Boussinesq assumption'. The only term that then retains the full variation
1325  in $\rho $ is the gravitational acceleration:  in $\rho $ is the gravitational acceleration:
1326  \begin{eqnarray}  \begin{eqnarray}
1327  \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}}
1328  _{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}}}
1329  \label{eq-zcb-hmom} \\  \label{eq-zcb-hmom} \\
1330  \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}}
1331  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1332  \label{eq-zcb-hydro} \\  \label{eq-zcb-hydro} \\
1333  \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{
1334  \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} \\
1335  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\
1336  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\
1337  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}
1338  \end{eqnarray}  \end{eqnarray}
1339  These equations still retain acoustic modes. But, because the  These equations still retain acoustic modes. But, because the
1340  ``compressible'' terms are linearized, the pressure equation \ref%  ``compressible'' terms are linearized, the pressure equation \ref
1341  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent
1342  term appears as a Helmholtz term in the non-hydrostatic pressure equation).  term appears as a Helmholtz term in the non-hydrostatic pressure equation).
1343  These are the \emph{truly} compressible Boussinesq equations. Note that the  These are the \emph{truly} compressible Boussinesq equations. Note that the
1344  EOS must have the same pressure dependency as the linearized pressure term,  EOS must have the same pressure dependency as the linearized pressure term,
1345  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{%  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{
1346  c_{s}^{2}}$, for consistency.  c_{s}^{2}}$, for consistency.
1347    
1348  \subsubsection{`Anelastic' z-coordinate equations}  \subsubsection{`Anelastic' z-coordinate equations}
1349    
1350  The anelastic approximation filters the acoustic mode by removing the  The anelastic approximation filters the acoustic mode by removing the
1351  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}%  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}
1352  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}%  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}
1353  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between
1354  continuity and EOS. A better solution is to change the dependency on  continuity and EOS. A better solution is to change the dependency on
1355  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
1356  height and a perturbation:  height and a perturbation:
1357  \begin{equation*}  \begin{equation*}
1358  \rho =\rho (\theta ,S,p_{o}(z)+\epsilon _{s}p^{\prime })  \rho =\rho (\theta ,S,p_{o}(z)+\epsilon _{s}p^{\prime })
1359  \end{equation*}  \end{equation*}
1360  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from
1361  differentiating the EOS, the continuity equation then becomes:  differentiating the EOS, the continuity equation then becomes:
1362  \begin{equation*}  \begin{equation*}
1363  \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{
1364  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+%  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+
1365  \frac{\partial w}{\partial z}=0  \frac{\partial w}{\partial z}=0
1366  \end{equation*}  \end{equation*}
1367  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
1368  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},%  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},
1369  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and
1370  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{%  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{
1371  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta
1372  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon
1373  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation
1374  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
1375  anelastic continuity equation:  anelastic continuity equation:
1376  \begin{equation}  \begin{equation}
1377  \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}-
1378  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}
1379  \end{equation}  \end{equation}
1380  A slightly different route leads to the quasi-Boussinesq continuity equation  A slightly different route leads to the quasi-Boussinesq continuity equation
1381  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+%  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+
1382  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }%  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }
1383  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:
1384  \begin{equation}  \begin{equation}
1385  \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{
1386  \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}
1387  \end{equation}  \end{equation}
1388  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 1278  equation if: Line 1391  equation if:
1391  \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}}
1392  \end{equation}  \end{equation}
1393  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$
1394  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 $\frac{
1395  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The
1396  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are
1397  then:  then:
1398  \begin{eqnarray}  \begin{eqnarray}
1399  \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}}
1400  _{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}}}
1401  \label{eq-zab-hmom} \\  \label{eq-zab-hmom} \\
1402  \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}}
1403  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1404  \label{eq-zab-hydro} \\  \label{eq-zab-hydro} \\
1405  \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{
1406  \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} \\
1407  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\
1408  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\
# Line 1302  Here, the objective is to drop the depth Line 1415  Here, the objective is to drop the depth
1415  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
1416  yield the ``truly'' incompressible Boussinesq equations:  yield the ``truly'' incompressible Boussinesq equations:
1417  \begin{eqnarray}  \begin{eqnarray}
1418  \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}}
1419  _{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}}}
1420  \label{eq-ztb-hmom} \\  \label{eq-ztb-hmom} \\
1421  \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}}
1422  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1423  \label{eq-ztb-hydro} \\  \label{eq-ztb-hydro} \\
1424  \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 1324  retain compressibility effects in the de Line 1437  retain compressibility effects in the de
1437  density thus:  density thus:
1438  \begin{equation*}  \begin{equation*}
1439  \rho =\rho _{o}+\rho ^{\prime }  \rho =\rho _{o}+\rho ^{\prime }
1440  \end{equation*}%  \end{equation*}
1441  We then assert that variations with depth of $\rho _{o}$ are unimportant  We then assert that variations with depth of $\rho _{o}$ are unimportant
1442  while the compressible effects in $\rho ^{\prime }$ are:  while the compressible effects in $\rho ^{\prime }$ are:
1443  \begin{equation*}  \begin{equation*}
1444  \rho _{o}=\rho _{c}  \rho _{o}=\rho _{c}
1445  \end{equation*}%  \end{equation*}
1446  \begin{equation*}  \begin{equation*}
1447  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}
1448  \end{equation*}%  \end{equation*}
1449  This then yields what we can call the semi-compressible Boussinesq  This then yields what we can call the semi-compressible Boussinesq
1450  equations:  equations:
1451  \begin{eqnarray}  \begin{eqnarray}
1452  \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}}
1453  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{%  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{
1454  \mathcal{F}}}  \label{eq:ocean-mom} \\  \mathcal{F}}}  \label{eq:ocean-mom} \\
1455  \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
1456  _{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 1348  _{c}}\frac{\partial p^{\prime }}{\partia Line 1461  _{c}}\frac{\partial p^{\prime }}{\partia
1461  \\  \\
1462  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\
1463  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}
1464  \end{eqnarray}%  \end{eqnarray}
1465  Note that the hydrostatic pressure of the resting fluid, including that  Note that the hydrostatic pressure of the resting fluid, including that
1466  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
1467  dynamics.  dynamics.
# Line 1372  In spherical coordinates, the velocity c Line 1485  In spherical coordinates, the velocity c
1485  and vertical direction respectively, are given by (see Fig.2) :  and vertical direction respectively, are given by (see Fig.2) :
1486    
1487  \begin{equation*}  \begin{equation*}
1488  u=r\cos \phi \frac{D\lambda }{Dt}  u=r\cos \varphi \frac{D\lambda }{Dt}
1489  \end{equation*}  \end{equation*}
1490    
1491  \begin{equation*}  \begin{equation*}
1492  v=r\frac{D\phi }{Dt}\qquad  v=r\frac{D\varphi }{Dt}\qquad
1493  \end{equation*}  \end{equation*}
1494  $\qquad \qquad \qquad \qquad $  $\qquad \qquad \qquad \qquad $
1495    
1496  \begin{equation*}  \begin{equation*}
1497  \dot{r}=\frac{Dr}{Dt}  \dot{r}=\frac{Dr}{Dt}
1498  \end{equation*}  \end{equation*}
1499    
1500  Here $\phi $ is the latitude, $\lambda $ the longitude, $r$ the radial  Here $\varphi $ is the latitude, $\lambda $ the longitude, $r$ the radial
1501  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
1502  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.
1503    
# Line 1392  The `grad' ($\nabla $) and `div' ($\nabl Line 1505  The `grad' ($\nabla $) and `div' ($\nabl
1505  spherical coordinates:  spherical coordinates:
1506    
1507  \begin{equation*}  \begin{equation*}
1508  \nabla \equiv \left( \frac{1}{r\cos \phi }\frac{\partial }{\partial \lambda }%  \nabla \equiv \left( \frac{1}{r\cos \varphi }\frac{\partial }{\partial \lambda }
1509  ,\frac{1}{r}\frac{\partial }{\partial \phi },\frac{\partial }{\partial r}%  ,\frac{1}{r}\frac{\partial }{\partial \varphi },\frac{\partial }{\partial r}
1510  \right)  \right)
1511  \end{equation*}  \end{equation*}
1512    
1513  \begin{equation*}  \begin{equation*}
1514  \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
1515  \lambda }+\frac{\partial }{\partial \phi }\left( v\cos \phi \right) \right\}  \lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\}
1516  +\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}
1517  \end{equation*}  \end{equation*}
1518    
1519  %%%% \end{document}  %tci%\end{document}

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