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 %%%% \begin{document}  
 %%%%  
 %%%% \tableofcontents  
31    
32  \pagebreak  %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    
52  MITgcm has a number of novel aspects:  MITgcm has a number of novel aspects:
53    
54  \begin{itemize}  \begin{itemize}
55  \item it can be used to study both atmospheric and oceanic phenomena; one  \item it can be used to study both atmospheric and oceanic phenomena; one
56  hydrodynamical kernel is used to drive forward both atmospheric and oceanic  hydrodynamical kernel is used to drive forward both atmospheric and oceanic
57  models - see fig.1%  models - see fig \ref{fig:onemodel}
58  \marginpar{  
59  Fig.1 One model}\ref{fig:onemodel}  %% CNHbegin
60    \input{part1/one_model_figure}
61  \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}  
62    
63  \item it has a non-hydrostatic capability and so can be used to study both  \item it has a non-hydrostatic capability and so can be used to study both
64  small-scale and large scale processes - see fig.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}  
65    
66    %% CNHbegin
67    \input{part1/all_scales_figure}
68    %% CNHend
69    
70  \item finite volume techniques are employed yielding an intuitive  \item finite volume techniques are employed yielding an intuitive
71  discretization and support for the treatment of irregular geometries using  discretization and support for the treatment of irregular geometries using
72  orthogonal curvilinear grids and shaved cells - see fig.3%  orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes}
73  \marginpar{  
74  Fig.3 Finite volumes}\ref{fig:Finite volumes}  %% CNHbegin
75    \input{part1/fvol_figure}
76    %% CNHend
77    
78  \item tangent linear and adjoint counterparts are automatically maintained  \item tangent linear and adjoint counterparts are automatically maintained
79  along with the forward model, permitting sensitivity and optimization  along with the forward model, permitting sensitivity and optimization
# Line 130  computational platforms. Line 84  computational platforms.
84  \end{itemize}  \end{itemize}
85    
86  Key publications reporting on and charting the development of the model are  Key publications reporting on and charting the development of the model are
87  listed in an Appendix.  \cite{hill:95,marshall:97a,marshall:97b,adcroft:97,marshall:98,adcroft:99,hill:99,maro-eta:99}:
88    
89    \begin{verbatim}
90    Hill, C. and J. Marshall, (1995)
91    Application of a Parallel Navier-Stokes Model to Ocean Circulation in
92    Parallel Computational Fluid Dynamics
93    In Proceedings of Parallel Computational Fluid Dynamics: Implementations
94    and Results Using Parallel Computers, 545-552.
95    Elsevier Science B.V.: New York
96    
97    Marshall, J., C. Hill, L. Perelman, and A. Adcroft, (1997)
98    Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling
99    J. Geophysical Res., 102(C3), 5733-5752.
100    
101    Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, (1997)
102    A finite-volume, incompressible Navier Stokes model for studies of the ocean
103    on parallel computers,
104    J. Geophysical Res., 102(C3), 5753-5766.
105    
106    Adcroft, A.J., Hill, C.N. and J. Marshall, (1997)
107    Representation of topography by shaved cells in a height coordinate ocean
108    model
109    Mon Wea Rev, vol 125, 2293-2315
110    
111    Marshall, J., Jones, H. and C. Hill, (1998)
112    Efficient ocean modeling using non-hydrostatic algorithms
113    Journal of Marine Systems, 18, 115-134
114    
115    Adcroft, A., Hill C. and J. Marshall: (1999)
116    A new treatment of the Coriolis terms in C-grid models at both high and low
117    resolutions,
118    Mon. Wea. Rev. Vol 127, pages 1928-1936
119    
120    Hill, C, Adcroft,A., Jamous,D., and J. Marshall, (1999)
121    A Strategy for Terascale Climate Modeling.
122    In Proceedings of the Eighth ECMWF Workshop on the Use of Parallel Processors
123    in Meteorology, pages 406-425
124    World Scientific Publishing Co: UK
125    
126    Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999)
127    Construction of the adjoint MIT ocean general circulation model and
128    application to Atlantic heat transport variability
129    J. Geophysical Res., 104(C12), 29,529-29,547.
130    
131    \end{verbatim}
132    
133  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
134  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  
135    
136  % $Header$  % $Header$
137  % $Name$  % $Name$
# Line 143  give a feel for the wide range of proble Line 140  give a feel for the wide range of proble
140    
141  The MITgcm has been designed and used to model a wide range of phenomena,  The MITgcm has been designed and used to model a wide range of phenomena,
142  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
143  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
144  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
145  of them here. A more detailed description of the underlying formulation,  of them here. A more detailed description of the underlying formulation,
146  numerical algorithm and implementation that lie behind these calculations is  numerical algorithm and implementation that lie behind these calculations is
147  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
148  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
149  with a FORTRAN\ 77 compiler) and follow the examples.  running Linux, together with a FORTRAN\ 77 compiler) and follow the examples
150    described in detail in the documentation.
151    
152  \subsection{Global atmosphere: `Held-Suarez' benchmark}  \subsection{Global atmosphere: `Held-Suarez' benchmark}
153    
154  Fig.E1a.\ref{fig:Held-Suarez} is an instaneous plot of the 500$mb$ height  A novel feature of MITgcm is its ability to simulate, using one basic algorithm,
155  field obtained using a 5-level version of the atmospheric pressure isomorph  both atmospheric and oceanographic flows at both small and large scales.
 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}  
156    
157  \subsection{Ocean gyres}  Figure \ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$
158    temperature field obtained using the atmospheric isomorph of MITgcm run at
159    2.8$^{\circ }$ resolution on the cubed sphere. We see cold air over the pole
160    (blue) and warm air along an equatorial band (red). Fully developed
161    baroclinic eddies spawned in the northern hemisphere storm track are
162    evident. There are no mountains or land-sea contrast in this calculation,
163    but you can easily put them in. The model is driven by relaxation to a
164    radiative-convective equilibrium profile, following the description set out
165    in Held and Suarez; 1994 designed to test atmospheric hydrodynamical cores -
166    there are no mountains or land-sea contrast.
167    
168    %% CNHbegin
169    \input{part1/cubic_eddies_figure}
170    %% CNHend
171    
172    As described in Adcroft (2001), a `cubed sphere' is used to discretize the
173    globe permitting a uniform griding and obviated the need to Fourier filter.
174    The `vector-invariant' form of MITgcm supports any orthogonal curvilinear
175    grid, of which the cubed sphere is just one of many choices.
176    
177    Figure \ref{fig:hs_zave_u} shows the 5-year mean, zonally averaged zonal
178    wind from a 20-level configuration of
179    the model. It compares favorable with more conventional spatial
180    discretization approaches. The two plots show the field calculated using the
181    cube-sphere grid and the flow calculated using a regular, spherical polar
182    latitude-longitude grid. Both grids are supported within the model.
183    
184    %% CNHbegin
185    \input{part1/hs_zave_u_figure}
186    %% CNHend
187    
188  \subsection{Global ocean circulation}  \subsection{Ocean gyres}
189    
190  Fig.E2a shows the pattern of ocean currents at the surface of a 4$^{\circ }$  Baroclinic instability is a ubiquitous process in the ocean, as well as the
191  global ocean model run with 15 vertical levels. The model is driven using  atmosphere. Ocean eddies play an important role in modifying the
192  monthly-mean winds with mixed boundary conditions on temperature and  hydrographic structure and current systems of the oceans. Coarse resolution
193  salinity at the surface. Fig.E2b shows the overturning (thermohaline)  models of the oceans cannot resolve the eddy field and yield rather broad,
194  circulation. Lopped cells are used to represent topography on a regular $%  diffusive patterns of ocean currents. But if the resolution of our models is
195  lat-lon$ grid extending from 70$^{\circ }N$ to 70$^{\circ }S$.  increased until the baroclinic instability process is resolved, numerical
196    solutions of a different and much more realistic kind, can be obtained.
197    
198  \begin{figure}  Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity
199  \begin{center}  field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal
200  \resizebox{!}{4in}{  resolution on a $lat-lon$
201  % \rotatebox{90}{  grid in which the pole has been rotated by 90$^{\circ }$ on to the equator
202    \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/ocean_circ_455_2030.eps}  (to avoid the converging of meridian in northern latitudes). 21 vertical
203  % }  levels are used in the vertical with a `lopped cell' representation of
204  }  topography. The development and propagation of anomalously warm and cold
205  \end{center}  eddies can be clearly seen in the Gulf Stream region. The transport of
206  \label{fig:horizcirc}  warm water northward by the mean flow of the Gulf Stream is also clearly
207  \end{figure}  visible.
208    
209  \begin{figure}  %% CNHbegin
210  \begin{center}  \input{part1/atl6_figure}
211  \resizebox{!}{4in}{  %% CNHend
  \rotatebox{90}{  
  \rotatebox{180}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/moc.eps}  
  }  
  }  
 }  
 \end{center}  
 \label{fig:moc}  
 \end{figure}  
   
   
 \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  
212    
 \subsection{Boundary forced internal waves}  
213    
214  \subsection{Carbon outgassing sensitivity}  \subsection{Global ocean circulation}
215    
216  Fig.E4 shows....  Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean currents at
217    the surface of a 4$^{\circ }$
218    global ocean model run with 15 vertical levels. Lopped cells are used to
219    represent topography on a regular $lat-lon$ grid extending from 70$^{\circ
220    }N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with
221    mixed boundary conditions on temperature and salinity at the surface. The
222    transfer properties of ocean eddies, convection and mixing is parameterized
223    in this model.
224    
225    Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning
226    circulation of the global ocean in Sverdrups.
227    
228    %%CNHbegin
229    \input{part1/global_circ_figure}
230    %%CNHend
231    
232    \subsection{Convection and mixing over topography}
233    
234    Dense plumes generated by localized cooling on the continental shelf of the
235    ocean may be influenced by rotation when the deformation radius is smaller
236    than the width of the cooling region. Rather than gravity plumes, the
237    mechanism for moving dense fluid down the shelf is then through geostrophic
238    eddies. The simulation shown in the figure \ref{fig:convect-and-topo}
239    (blue is cold dense fluid, red is
240    warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to
241    trigger convection by surface cooling. The cold, dense water falls down the
242    slope but is deflected along the slope by rotation. It is found that
243    entrainment in the vertical plane is reduced when rotational control is
244    strong, and replaced by lateral entrainment due to the baroclinic
245    instability of the along-slope current.
246    
247    %%CNHbegin
248    \input{part1/convect_and_topo}
249    %%CNHend
250    
251  \begin{figure}  \subsection{Boundary forced internal waves}
 \begin{center}  
 \resizebox{!}{4in}{  
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]{part1/co209.eps}  
 }  
 \end{center}  
 \label{fig:co2mrt}  
 \end{figure}  
252    
253    The unique ability of MITgcm to treat non-hydrostatic dynamics in the
254    presence of complex geometry makes it an ideal tool to study internal wave
255    dynamics and mixing in oceanic canyons and ridges driven by large amplitude
256    barotropic tidal currents imposed through open boundary conditions.
257    
258    Fig. \ref{fig:boundary-forced-wave} shows the influence of cross-slope
259    topographic variations on
260    internal wave breaking - the cross-slope velocity is in color, the density
261    contoured. The internal waves are excited by application of open boundary
262    conditions on the left. They propagate to the sloping boundary (represented
263    using MITgcm's finite volume spatial discretization) where they break under
264    nonhydrostatic dynamics.
265    
266    %%CNHbegin
267    \input{part1/boundary_forced_waves}
268    %%CNHend
269    
270    \subsection{Parameter sensitivity using the adjoint of MITgcm}
271    
272    Forward and tangent linear counterparts of MITgcm are supported using an
273    `automatic adjoint compiler'. These can be used in parameter sensitivity and
274    data assimilation studies.
275    
276    As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity}
277    maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude
278    of the overturning stream-function shown in figure \ref{fig:large-scale-circ}
279    at 60$^{\circ }$N and $
280    \mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over
281    a 100 year period. We see that $J$ is
282    sensitive to heat fluxes over the Labrador Sea, one of the important sources
283    of deep water for the thermohaline circulations. This calculation also
284    yields sensitivities to all other model parameters.
285    
286    %%CNHbegin
287    \input{part1/adj_hf_ocean_figure}
288    %%CNHend
289    
290    \subsection{Global state estimation of the ocean}
291    
292    An important application of MITgcm is in state estimation of the global
293    ocean circulation. An appropriately defined `cost function', which measures
294    the departure of the model from observations (both remotely sensed and
295    in-situ) over an interval of time, is minimized by adjusting `control
296    parameters' such as air-sea fluxes, the wind field, the initial conditions
297    etc. Figure \ref{fig:assimilated-globes} shows the large scale planetary
298    circulation and a Hopf-Muller plot of Equatorial sea-surface height.
299    Both are obtained from assimilation bringing the model in to
300    consistency with altimetric and in-situ observations over the period
301    1992-1997.
302    
303    %% CNHbegin
304    \input{part1/assim_figure}
305    %% CNHend
306    
307    \subsection{Ocean biogeochemical cycles}
308    
309    MITgcm is being used to study global biogeochemical cycles in the ocean. For
310    example one can study the effects of interannual changes in meteorological
311    forcing and upper ocean circulation on the fluxes of carbon dioxide and
312    oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows
313    the annual air-sea flux of oxygen and its relation to density outcrops in
314    the southern oceans from a single year of a global, interannually varying
315    simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution
316    telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown).
317    
318    %%CNHbegin
319    \input{part1/biogeo_figure}
320    %%CNHend
321    
322    \subsection{Simulations of laboratory experiments}
323    
324    Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a
325    laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An
326    initially homogeneous tank of water ($1m$ in diameter) is driven from its
327    free surface by a rotating heated disk. The combined action of mechanical
328    and thermal forcing creates a lens of fluid which becomes baroclinically
329    unstable. The stratification and depth of penetration of the lens is
330    arrested by its instability in a process analogous to that which sets the
331    stratification of the ACC.
332    
333    %%CNHbegin
334    \input{part1/lab_figure}
335    %%CNHend
336    
337  % $Header$  % $Header$
338  % $Name$  % $Name$
# Line 262  Fig.E4 shows.... Line 341  Fig.E4 shows....
341    
342  To render atmosphere and ocean models from one dynamical core we exploit  To render atmosphere and ocean models from one dynamical core we exploit
343  `isomorphisms' between equation sets that govern the evolution of the  `isomorphisms' between equation sets that govern the evolution of the
344  respective fluids - see fig.4%  respective fluids - see figure \ref{fig:isomorphic-equations}.
345  \marginpar{  One system of hydrodynamical equations is written down
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down  
346  and encoded. The model variables have different interpretations depending on  and encoded. The model variables have different interpretations depending on
347  whether the atmosphere or ocean is being studied. Thus, for example, the  whether the atmosphere or ocean is being studied. Thus, for example, the
348  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are
349  modeling the atmosphere and height, $z$, if we are modeling the ocean.  modeling the atmosphere (right hand side of figure \ref{fig:isomorphic-equations})
350    and height, $z$, if we are modeling the ocean (left hand side of figure
351    \ref{fig:isomorphic-equations}).
352    
353    %%CNHbegin
354    \input{part1/zandpcoord_figure.tex}
355    %%CNHend
356    
357  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
358  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 360  velocity $\vec{\mathbf{v}}$, active trac
360  depend on $\theta $, $S$, and $p$. The equations that govern the evolution  depend on $\theta $, $S$, and $p$. The equations that govern the evolution
361  of these fields, obtained by applying the laws of classical mechanics and  of these fields, obtained by applying the laws of classical mechanics and
362  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of
363  a generic vertical coordinate, $r$, see fig.5%  a generic vertical coordinate, $r$, so that the appropriate
364  \marginpar{  kinematic boundary conditions can be applied isomorphically
365  Fig.5 The vertical coordinate of model}:  see figure \ref{fig:zandp-vert-coord}.
366    
367  \begin{figure}  %%CNHbegin
368  \begin{center}  \input{part1/vertcoord_figure.tex}
369  \resizebox{!}{4in}{  %%CNHend
  \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*}  
370    
371  \begin{equation*}  \begin{equation*}
372  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{%  \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}
373  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{  \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}
374  vertical mtm}  \text{ horizontal mtm} \label{eq:horizontal_mtm}
375  \end{equation*}  \end{equation*}
376    
377  \begin{equation}  \begin{equation}
378  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{%  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{
379  \partial r}=0\text{ continuity}  \label{eq:continuous}  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{
380    vertical mtm} \label{eq:vertical_mtm}
381  \end{equation}  \end{equation}
382    
383  \begin{equation*}  \begin{equation}
384  b=b(\theta ,S,r)\text{ equation of state}  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{
385  \end{equation*}  \partial r}=0\text{ continuity}  \label{eq:continuity}
386    \end{equation}
387    
388  \begin{equation*}  \begin{equation}
389  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{  potential temperature}  b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state}
390  \end{equation*}  \end{equation}
391    
392  \begin{equation*}  \begin{equation}
393  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{  humidity/salinity}  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}
394  \end{equation*}  \label{eq:potential_temperature}
395    \end{equation}
396    
397    \begin{equation}
398    \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}
399    \label{eq:humidity_salt}
400    \end{equation}
401    
402  Here:  Here:
403    
404  \begin{equation*}  \begin{equation*}
405  r\text{ is the vertical coordinate}  r\text{ is the vertical coordinate}
406  \end{equation*}  \end{equation*}
407    
408  \begin{equation*}  \begin{equation*}
409  \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{
410  is the total derivative}  is the total derivative}
411  \end{equation*}  \end{equation*}
412    
413  \begin{equation*}  \begin{equation*}
414  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}%  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}
415  \text{ is the `grad' operator}  \text{ is the `grad' operator}
416  \end{equation*}  \end{equation*}
417  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}%  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}
418  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$
419  is a unit vector in the vertical  is a unit vector in the vertical
420    
421  \begin{equation*}  \begin{equation*}
422  t\text{ is time}  t\text{ is time}
423  \end{equation*}  \end{equation*}
424    
425  \begin{equation*}  \begin{equation*}
426  \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
427  velocity}  velocity}
428  \end{equation*}  \end{equation*}
429    
430  \begin{equation*}  \begin{equation*}
431  \phi \text{ is the `pressure'/`geopotential'}  \phi \text{ is the `pressure'/`geopotential'}
432  \end{equation*}  \end{equation*}
433    
434  \begin{equation*}  \begin{equation*}
435  \vec{\Omega}\text{ is the Earth's rotation}  \vec{\Omega}\text{ is the Earth's rotation}
436  \end{equation*}  \end{equation*}
437    
438  \begin{equation*}  \begin{equation*}
439  b\text{ is the `buoyancy'}  b\text{ is the `buoyancy'}
440  \end{equation*}  \end{equation*}
441    
442  \begin{equation*}  \begin{equation*}
443  \theta \text{ is potential temperature}  \theta \text{ is potential temperature}
444  \end{equation*}  \end{equation*}
445    
446  \begin{equation*}  \begin{equation*}
447  S\text{ is specific humidity in the atmosphere; salinity in the ocean}  S\text{ is specific humidity in the atmosphere; salinity in the ocean}
448  \end{equation*}  \end{equation*}
449    
450  \begin{equation*}  \begin{equation*}
451  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{%  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{
452  \mathbf{v}}  \mathbf{v}}
453  \end{equation*}  \end{equation*}
454    
455  \begin{equation*}  \begin{equation*}
456  \mathcal{Q}_{\theta }\mathcal{\ }\text{are forcing and dissipation of }%  \mathcal{Q}_{\theta }\mathcal{\ }\text{are forcing and dissipation of }\theta
 \theta  
457  \end{equation*}  \end{equation*}
458    
459  \begin{equation*}  \begin{equation*}
# Line 385  S\text{ is specific humidity in the atmo Line 461  S\text{ is specific humidity in the atmo
461  \end{equation*}  \end{equation*}
462    
463  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
464  extensive `physics' packages for atmosphere and ocean described in Chapter 6.  `physics' and forcing packages for atmosphere and ocean. These are described
465    in later chapters.
466    
467  \subsection{Kinematic Boundary conditions}  \subsection{Kinematic Boundary conditions}
468    
469  \subsubsection{vertical}  \subsubsection{vertical}
470    
471  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}):
472    
473  \begin{equation}  \begin{equation}
474  \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)}
475  \label{eq:fixedbc}  \label{eq:fixedbc}
476  \end{equation}  \end{equation}
477    
478  \begin{equation}  \begin{equation}
479  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \  \dot{r}=\frac{Dr}{Dt} \text{\ at\ } r=R_{moving}\text{ \
480  (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc}  (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc}
481  \end{equation}  \end{equation}
482    
483  Here  Here
484    
485  \begin{equation*}  \begin{equation*}
486  R_{moving}=R_{o}+\eta  R_{moving}=R_{o}+\eta
487  \end{equation*}  \end{equation*}
488  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
489  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 494  of motion.
494    
495  \begin{equation}  \begin{equation}
496  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}
497  \end{equation}%  \end{equation}
498  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.
499    
500  \subsection{Atmosphere}  \subsection{Atmosphere}
501    
502  In the atmosphere, see fig.5, we interpret:  In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret:
503    
504  \begin{equation}  \begin{equation}
505  r=p\text{ is the pressure}  \label{eq:atmos-r}  r=p\text{ is the pressure}  \label{eq:atmos-r}
# Line 454  where Line 531  where
531    
532  \begin{equation*}  \begin{equation*}
533  T\text{ is absolute temperature}  T\text{ is absolute temperature}
534  \end{equation*}%  \end{equation*}
535  \begin{equation*}  \begin{equation*}
536  p\text{ is the pressure}  p\text{ is the pressure}
537  \end{equation*}%  \end{equation*}
538  \begin{eqnarray*}  \begin{eqnarray*}
539  &&z\text{ is the height of the pressure surface} \\  &&z\text{ is the height of the pressure surface} \\
540  &&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 544  In the above the ideal gas law, $p=\rho
544  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)
545  \begin{equation}  \begin{equation}
546  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}
547  \end{equation}%  \end{equation}
548  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
549  constant and $c_{p}$ the specific heat of air at constant pressure.  constant and $c_{p}$ the specific heat of air at constant pressure.
550    
551  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):
552    
553  \begin{equation*}  \begin{equation*}
554  R_{fixed}=p_{top}=0  R_{fixed}=p_{top}=0
555  \end{equation*}  \end{equation*}
556  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
557  given by  given by
558  \begin{equation*}  \begin{equation*}
559  R_{moving}=R_{o}(x,y)=p_{o}(x,y)  R_{moving}=R_{o}(x,y)=p_{o}(x,y)
560  \end{equation*}  \end{equation*}
561  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
562  atmosphere.  atmosphere.
# Line 493  The boundary conditions at top and botto Line 570  The boundary conditions at top and botto
570  atmosphere)}  \label{eq:moving-bc-atmos}  atmosphere)}  \label{eq:moving-bc-atmos}
571  \end{eqnarray}  \end{eqnarray}
572    
573  Then the (hydrostatic form of) eq(\ref{eq:continuous}) yields a consistent  Then the (hydrostatic form of) equations (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt})
574  set of atmospheric equations which, for convenience, are written out in $p$  yields a consistent set of atmospheric equations which, for convenience, are written out in $p$
575  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).
576    
577  \subsection{Ocean}  \subsection{Ocean}
# Line 517  At the bottom of the ocean: $R_{fixed}(x Line 594  At the bottom of the ocean: $R_{fixed}(x
594    
595  The surface of the ocean is given by: $R_{moving}=\eta $  The surface of the ocean is given by: $R_{moving}=\eta $
596    
597  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 $
598  R_{o}=Z_{o}=0$.  R_{o}=Z_{o}=0$.
599    
600  Boundary conditions are:  Boundary conditions are:
# Line 525  Boundary conditions are: Line 602  Boundary conditions are:
602  \begin{eqnarray}  \begin{eqnarray}
603  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}
604  \\  \\
605  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)
606  \label{eq:moving-bc-ocean}}  \label{eq:moving-bc-ocean}}
607  \end{eqnarray}  \end{eqnarray}
608  where $\eta $ is the elevation of the free surface.  where $\eta $ is the elevation of the free surface.
609    
610  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
611    of oceanic equations
612  which, for convenience, are written out in $z$ coordinates in Appendix Ocean  which, for convenience, are written out in $z$ coordinates in Appendix Ocean
613  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).
614    
# Line 542  Let us separate $\phi $ in to surface, h Line 620  Let us separate $\phi $ in to surface, h
620  \begin{equation}  \begin{equation}
621  \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)
622  \label{eq:phi-split}  \label{eq:phi-split}
623  \end{equation}%  \end{equation}
624  and write eq(\ref{incompressible}a,b) in the form:  and write eq(\ref{eq:incompressible}) in the form:
625    
626  \begin{equation}  \begin{equation}
627  \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 634  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l
634  \end{equation}  \end{equation}
635    
636  \begin{equation}  \begin{equation}
637  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{%  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{
638  \partial r}=G_{\dot{r}}  \label{eq:mom-w}  \partial r}=G_{\dot{r}}  \label{eq:mom-w}
639  \end{equation}  \end{equation}
640  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.
641    
642  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
643  {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
644  terms in the momentum equations. In spherical coordinates they take the form%  terms in the momentum equations. In spherical coordinates they take the form
645  \footnote{%  \footnote{
646  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms
647  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref%  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref
648  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in
649  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (%  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (
650  \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
651  discussion:  discussion:
652    
# Line 576  discussion: Line 654  discussion:
654  \left.  \left.
655  \begin{tabular}{l}  \begin{tabular}{l}
656  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\
657  $-\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\} $
658  \\  \\
659  $-\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\} $
660  \\  \\
661  $+\mathcal{F}_{u}$%  $+\mathcal{F}_{u}$
662  \end{tabular}%  \end{tabular}
663  \ \right\} \left\{  \ \right\} \left\{
664  \begin{tabular}{l}  \begin{tabular}{l}
665  \textit{advection} \\  \textit{advection} \\
666  \textit{metric} \\  \textit{metric} \\
667  \textit{Coriolis} \\  \textit{Coriolis} \\
668  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
669  \end{tabular}%  \end{tabular}
670  \ \right. \qquad   \label{eq:gu-speherical}  \ \right. \qquad  \label{eq:gu-speherical}
671  \end{equation}  \end{equation}
672    
673  \begin{equation}  \begin{equation}
674  \left.  \left.
675  \begin{tabular}{l}  \begin{tabular}{l}
676  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\
677  $-\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\}
678  $ \\  $ \\
679  $-\left\{ -2\Omega u\sin lat\right\} $ \\  $-\left\{ -2\Omega u\sin \varphi \right\} $ \\
680  $+\mathcal{F}_{v}$%  $+\mathcal{F}_{v}$
681  \end{tabular}%  \end{tabular}
682  \ \right\} \left\{  \ \right\} \left\{
683  \begin{tabular}{l}  \begin{tabular}{l}
684  \textit{advection} \\  \textit{advection} \\
685  \textit{metric} \\  \textit{metric} \\
686  \textit{Coriolis} \\  \textit{Coriolis} \\
687  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
688  \end{tabular}%  \end{tabular}
689  \ \right. \qquad   \label{eq:gv-spherical}  \ \right. \qquad  \label{eq:gv-spherical}
690  \end{equation}%  \end{equation}
691  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
692    
693  \begin{equation}  \begin{equation}
694  \left.  \left.
695  \begin{tabular}{l}  \begin{tabular}{l}
696  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\
697  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\
698  ${+}\underline{{2\Omega u\cos lat}}$ \\  ${+}\underline{{2\Omega u\cos \varphi}}$ \\
699  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$%  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$
700  \end{tabular}%  \end{tabular}
701  \ \right\} \left\{  \ \right\} \left\{
702  \begin{tabular}{l}  \begin{tabular}{l}
703  \textit{advection} \\  \textit{advection} \\
704  \textit{metric} \\  \textit{metric} \\
705  \textit{Coriolis} \\  \textit{Coriolis} \\
706  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
707  \end{tabular}%  \end{tabular}
708  \ \right.   \label{eq:gw-spherical}  \ \right.  \label{eq:gw-spherical}
709  \end{equation}%  \end{equation}
710  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
711    
712  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 `$\varphi$
713  ' is latitude.  ' is latitude.
714    
715  Grad and div operators in spherical coordinates are defined in appendix  Grad and div operators in spherical coordinates are defined in appendix
716  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}  
717    
718    %%CNHbegin
719    \input{part1/sphere_coord_figure.tex}
720    %%CNHend
721    
722  \subsubsection{Shallow atmosphere approximation}  \subsubsection{Shallow atmosphere approximation}
723    
# Line 661  hydrostatic balance and the `traditional Line 727  hydrostatic balance and the `traditional
727  Coriolis force is treated approximately and the shallow atmosphere  Coriolis force is treated approximately and the shallow atmosphere
728  approximation is made.\ The MITgcm need not make the `traditional  approximation is made.\ The MITgcm need not make the `traditional
729  approximation'. To be able to support consistent non-hydrostatic forms the  approximation'. To be able to support consistent non-hydrostatic forms the
730  shallow atmosphere approximation can be relaxed - when dividing through by $r  shallow atmosphere approximation can be relaxed - when dividing through by $
731  $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$,  r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$,
732  the radius of the earth.  the radius of the earth.
733    
734  \subsubsection{Hydrostatic and quasi-hydrostatic forms}  \subsubsection{Hydrostatic and quasi-hydrostatic forms}
735    \label{sec:hydrostatic_and_quasi-hydrostatic_forms}
736    
737  These are discussed at length in Marshall et al (1997a).  These are discussed at length in Marshall et al (1997a).
738    
# Line 674  terms in Eqs. (\ref{eq:gu-speherical} $\ Line 741  terms in Eqs. (\ref{eq:gu-speherical} $\
741  are neglected and `${r}$' is replaced by `$a$', the mean radius of the  are neglected and `${r}$' is replaced by `$a$', the mean radius of the
742  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
743  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
744  computed at all other levels by integration of the hydrostatic relation, eq(%  computed at all other levels by integration of the hydrostatic relation, eq(
745  \ref{eq:hydrostatic}).  \ref{eq:hydrostatic}).
746    
747  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between
748  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
749  \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
750  contribution to the pressure field: only the terms underlined twice in Eqs. (%  contribution to the pressure field: only the terms underlined twice in Eqs. (
751  \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
752  and, simultaneously, the shallow atmosphere approximation is relaxed. In  and, simultaneously, the shallow atmosphere approximation is relaxed. In
753  \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 755  variation of the radial position of a pa
755  vertical momentum equation (\ref{eq:mom-w}) becomes:  vertical momentum equation (\ref{eq:mom-w}) becomes:
756    
757  \begin{equation*}  \begin{equation*}
758  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos lat  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos \varphi
759  \end{equation*}  \end{equation*}
760  making a small correction to the hydrostatic pressure.  making a small correction to the hydrostatic pressure.
761    
# Line 704  only a quasi-non-hydrostatic atmospheric Line 771  only a quasi-non-hydrostatic atmospheric
771    
772  \paragraph{Non-hydrostatic Ocean}  \paragraph{Non-hydrostatic Ocean}
773    
774  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref%  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref
775  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A
776  three dimensional elliptic equation must be solved subject to Neumann  three dimensional elliptic equation must be solved subject to Neumann
777  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
778  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
779  incompressible condition eq(\ref{eq:continuous})c has already filtered out  incompressible condition eq(\ref{eq:continuity}) has already filtered out
780  acoustic modes. It does, however, ensure that the gravity waves are treated  acoustic modes. It does, however, ensure that the gravity waves are treated
781  accurately with an exact dispersion relation. The \textbf{NH} set has a  accurately with an exact dispersion relation. The \textbf{NH} set has a
782  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 784  and Bromley, 1995; Marshall et.al.\ 1997
784    
785  \paragraph{Quasi-nonhydrostatic Atmosphere}  \paragraph{Quasi-nonhydrostatic Atmosphere}
786    
787  In the non-hydrostatic version of our atmospheric model we approximate $\dot{%  In the non-hydrostatic version of our atmospheric model we approximate $\dot{
788  r}$ 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})
789  (but only here) by:  (but only here) by:
790    
791  \begin{equation}  \begin{equation}
792  \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}
793  \end{equation}%  \end{equation}
794  where $p_{hy}$ is the hydrostatic pressure.  where $p_{hy}$ is the hydrostatic pressure.
795    
796  \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 818  equations in $z-$coordinates are support
818    
819  \subparagraph{Non-hydrostatic}  \subparagraph{Non-hydrostatic}
820    
821  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$%  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$
822  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref%  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref
823  {eq:ocean-salt}).  {eq:ocean-salt}).
824    
825  \subsection{Solution strategy}  \subsection{Solution strategy}
826    
827  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{
828  NH} models is summarized in Fig.7.%  NH} models is summarized in Figure \ref{fig:solution-strategy}.
829  \marginpar{  Under all dynamics, a 2-d elliptic equation is
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is  
830  first solved to find the surface pressure and the hydrostatic pressure at  first solved to find the surface pressure and the hydrostatic pressure at
831  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
832  \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 835  forward and $\dot{r}$ found from continu
835  stepping forward the horizontal momentum equations; $\dot{r}$ is found by  stepping forward the horizontal momentum equations; $\dot{r}$ is found by
836  stepping forward the vertical momentum equation.  stepping forward the vertical momentum equation.
837    
838  \begin{figure}  %%CNHbegin
839  \begin{center}  \input{part1/solution_strategy_figure.tex}
840  \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}  
   
841    
842  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
843  course, some complication that goes with the inclusion of $\cos \phi \ $%  course, some complication that goes with the inclusion of $\cos \varphi \ $
844  Coriolis terms and the relaxation of the shallow atmosphere approximation.  Coriolis terms and the relaxation of the shallow atmosphere approximation.
845  But this leads to negligible increase in computation. In \textbf{NH}, in  But this leads to negligible increase in computation. In \textbf{NH}, in
846  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 850  Marshall et al, 1997) resulting in a non
850  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.
851    
852  \subsection{Finding the pressure field}  \subsection{Finding the pressure field}
853    \label{sec:finding_the_pressure_field}
854    
855  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the
856  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 865  Hydrostatic pressure is obtained by inte
865  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:
866    
867  \begin{equation*}  \begin{equation*}
868  \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}
869  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr
870  \end{equation*}  \end{equation*}
871  and so  and so
872    
# Line 826  atmospheric pressure pushing down on the Line 883  atmospheric pressure pushing down on the
883    
884  \subsubsection{Surface pressure}  \subsubsection{Surface pressure}
885    
886  The surface pressure equation can be obtained by integrating continuity, (%  The surface pressure equation can be obtained by integrating continuity,
887  \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$  (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$
888    
889  \begin{equation*}  \begin{equation*}
890  \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}
891  }_{h}+\partial _{r}\dot{r}\right) dr=0  }_{h}+\partial _{r}\dot{r}\right) dr=0
892  \end{equation*}  \end{equation*}
893    
894  Thus:  Thus:
895    
896  \begin{equation*}  \begin{equation*}
897  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta
898  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}%  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}
899  _{h}dr=0  _{h}dr=0
900  \end{equation*}  \end{equation*}
901  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 $
902  r $. The above can be rearranged to yield, using Leibnitz's theorem:  r $. The above can be rearranged to yield, using Leibnitz's theorem:
903    
904  \begin{equation}  \begin{equation}
905  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot
906  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}
907  \label{eq:free-surface}  \label{eq:free-surface}
908  \end{equation}%  \end{equation}
909  where we have incorporated a source term.  where we have incorporated a source term.
910    
911  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential
912  (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can  (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can
913  be written  be written
914  \begin{equation}  \begin{equation}
915  \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)
916  \label{eq:phi-surf}  \label{eq:phi-surf}
917  \end{equation}%  \end{equation}
918  where $b_{s}$ is the buoyancy at the surface.  where $b_{s}$ is the buoyancy at the surface.
919    
920  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
921  {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
922  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free
923  surface' and `rigid lid' approaches are available.  surface' and `rigid lid' approaches are available.
924    
925  \subsubsection{Non-hydrostatic pressure}  \subsubsection{Non-hydrostatic pressure}
926    
927  Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{%  Taking the horizontal divergence of (\ref{eq:mom-h}) and adding
928  \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation  $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation
929  (\ref{incompressible}), we deduce that:  (\ref{eq:continuity}), we deduce that:
930    
931  \begin{equation}  \begin{equation}
932  \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{
933  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .%  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .
934  \vec{\mathbf{F}}  \label{eq:3d-invert}  \vec{\mathbf{F}}  \label{eq:3d-invert}
935  \end{equation}  \end{equation}
936    
# Line 893  coasts (in the ocean) and the bottom: Line 950  coasts (in the ocean) and the bottom:
950  \end{equation}  \end{equation}
951  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
952  kinematic condition (\ref{nonormalflow}) is also applied to the vertical  kinematic condition (\ref{nonormalflow}) is also applied to the vertical
953  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 $
954  \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
955  tangential component of velocity, $v_{T}$, at all solid boundaries,  tangential component of velocity, $v_{T}$, at all solid boundaries,
956  depending on the form chosen for the dissipative terms in the momentum  depending on the form chosen for the dissipative terms in the momentum
957  equations - see below.  equations - see below.
958    
959  Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that:  Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that:
960    
961  \begin{equation}  \begin{equation}
962  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}
# Line 910  where Line 967  where
967  \begin{equation*}  \begin{equation*}
968  \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
969  _{s}+\mathbf{\nabla }\phi _{hyd}\right)  _{s}+\mathbf{\nabla }\phi _{hyd}\right)
970  \end{equation*}%  \end{equation*}
971  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem
972  (\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
973  exploit classical 3D potential theory and, by introducing an appropriately  exploit classical 3D potential theory and, by introducing an appropriately
974  chosen $\delta $-function sheet of `source-charge', replace the inhomogenous  chosen $\delta $-function sheet of `source-charge', replace the
975  boundary condition on pressure by a homogeneous one. The source term $rhs$  inhomogeneous boundary condition on pressure by a homogeneous one. The
976  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 $
977  By simultaneously setting $%  \vec{\mathbf{F}}.$ By simultaneously setting $
978  \begin{array}{l}  \begin{array}{l}
979  \widehat{n}.\vec{\mathbf{F}}%  \widehat{n}.\vec{\mathbf{F}}
980  \end{array}%  \end{array}
981  =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
982  self-consistent but simpler homogenised Elliptic problem is obtained:  self-consistent but simpler homogenized Elliptic problem is obtained:
983    
984  \begin{equation*}  \begin{equation*}
985  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad
986  \end{equation*}%  \end{equation*}
987  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such
988  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
989  {eq:inhom-neumann-nh}) the modified boundary condition becomes:  {eq:inhom-neumann-nh}) the modified boundary condition becomes:
990    
991  \begin{equation}  \begin{equation}
# Line 939  If the flow is `close' to hydrostatic ba Line 996  If the flow is `close' to hydrostatic ba
996  converges rapidly because $\phi _{nh}\ $is then only a small correction to  converges rapidly because $\phi _{nh}\ $is then only a small correction to
997  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).
998    
999  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})
1000  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.
1001    
1002  \subsection{Forcing/dissipation}  \subsection{Forcing/dissipation}
# Line 947  does not vanish at $r=R_{moving}$, and s Line 1004  does not vanish at $r=R_{moving}$, and s
1004  \subsubsection{Forcing}  \subsubsection{Forcing}
1005    
1006  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
1007  `physics packages' described in detail in chapter ??.  `physics packages' and forcing packages. These are described later on.
1008    
1009  \subsubsection{Dissipation}  \subsubsection{Dissipation}
1010    
# Line 957  Many forms of momentum dissipation are a Line 1014  Many forms of momentum dissipation are a
1014  biharmonic frictions are commonly used:  biharmonic frictions are commonly used:
1015    
1016  \begin{equation}  \begin{equation}
1017  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}}
1018  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}
1019  \end{equation}  \end{equation}
1020  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 1025  friction. These coefficients are the sam
1025    
1026  The mixing terms for the temperature and salinity equations have a similar  The mixing terms for the temperature and salinity equations have a similar
1027  form to that of momentum except that the diffusion tensor can be  form to that of momentum except that the diffusion tensor can be
1028  non-diagonal and have varying coefficients. $\qquad $%  non-diagonal and have varying coefficients. $\qquad $
1029  \begin{equation}  \begin{equation}
1030  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
1031  _{h}^{4}(T,S)  \label{eq:diffusion}  _{h}^{4}(T,S)  \label{eq:diffusion}
1032  \end{equation}  \end{equation}
1033  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $%  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $
1034  horizontal coefficient for biharmonic diffusion. In the simplest case where  horizontal coefficient for biharmonic diffusion. In the simplest case where
1035  the subgrid-scale fluxes of heat and salt are parameterized with constant  the subgrid-scale fluxes of heat and salt are parameterized with constant
1036  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 1041  reduces to a diagonal matrix with consta
1041  \begin{array}{ccc}  \begin{array}{ccc}
1042  K_{h} & 0 & 0 \\  K_{h} & 0 & 0 \\
1043  0 & K_{h} & 0 \\  0 & K_{h} & 0 \\
1044  0 & 0 & K_{v}%  0 & 0 & K_{v}
1045  \end{array}  \end{array}
1046  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}
1047  \end{equation}  \end{equation}
# Line 994  salinity ... ). Line 1051  salinity ... ).
1051    
1052  \subsection{Vector invariant form}  \subsection{Vector invariant form}
1053    
1054  For some purposes it is advantageous to write momentum advection in eq(\ref%  For some purposes it is advantageous to write momentum advection in eq(\ref
1055  {hor-mtm}) and (\ref{vertmtm}) in the (so-called) `vector invariant' form:  {eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the (so-called) `vector invariant' form:
1056    
1057  \begin{equation}  \begin{equation}
1058  \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}
1059  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla %  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla
1060  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]
1061  \label{eq:vi-identity}  \label{eq:vi-identity}
1062  \end{equation}%  \end{equation}
1063  This permits alternative numerical treatments of the non-linear terms based  This permits alternative numerical treatments of the non-linear terms based
1064  on their representation as a vorticity flux. Because gradients of coordinate  on their representation as a vorticity flux. Because gradients of coordinate
1065  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
1066  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref%  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref
1067  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information
1068  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
1069  to discretize the model.  to discretize the model.
1070    
1071  \subsection{Adjoint}  \subsection{Adjoint}
1072    
1073  Tangent linear and adoint counterparts of the forward model and described in  Tangent linear and adjoint counterparts of the forward model are described
1074  Chapter 5.  in Chapter 5.
1075    
1076  % $Header$  % $Header$
1077  % $Name$  % $Name$
# Line 1028  coordinates} Line 1085  coordinates}
1085    
1086  The hydrostatic primitive equations (HPEs) in p-coordinates are:  The hydrostatic primitive equations (HPEs) in p-coordinates are:
1087  \begin{eqnarray}  \begin{eqnarray}
1088  \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}}
1089  _{h}+\mathbf{\nabla }_{p}\phi  &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}
1090  \label{eq:atmos-mom} \\  \label{eq:atmos-mom} \\
1091  \frac{\partial \phi }{\partial p}+\alpha  &=&0  \label{eq-p-hydro-start} \\  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\
1092  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1093  \partial p} &=&0  \label{eq:atmos-cont} \\  \partial p} &=&0  \label{eq:atmos-cont} \\
1094  p\alpha  &=&RT  \label{eq:atmos-eos} \\  p\alpha &=&RT  \label{eq:atmos-eos} \\
1095  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}
1096  \end{eqnarray}%  \end{eqnarray}
1097  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
1098  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot
1099  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total
1100  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
1101  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp%  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp
1102  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref%  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref
1103  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $%  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $
1104  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 $
1105  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.
1106    
1107  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 1109  $\theta $ so that it looks more like a g
1109  Differentiating (\ref{eq:atmos-eos}) we get:  Differentiating (\ref{eq:atmos-eos}) we get:
1110  \begin{equation*}  \begin{equation*}
1111  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}
1112  \end{equation*}%  \end{equation*}
1113  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 $
1114  c_{p}=c_{v}+R$, gives:  c_{p}=c_{v}+R$, gives:
1115  \begin{equation}  \begin{equation}
1116  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}
1117  \label{eq-p-heat-interim}  \label{eq-p-heat-interim}
1118  \end{equation}%  \end{equation}
1119  Potential temperature is defined:  Potential temperature is defined:
1120  \begin{equation}  \begin{equation}
1121  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}
1122  \end{equation}%  \end{equation}
1123  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
1124  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:
1125  \begin{equation}  \begin{equation}
1126  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}
1127  \end{equation}%  \end{equation}
1128  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
1129  the Exner function:  the Exner function:
1130  \begin{equation*}  \begin{equation*}
1131  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
1132  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{%  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{
1133  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}%  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}
1134  \frac{Dp}{Dt}  \frac{Dp}{Dt}
1135  \end{equation*}%  \end{equation*}
1136  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.
1137    
1138  The heat equation is obtained by noting that  The heat equation is obtained by noting that
1139  \begin{equation*}  \begin{equation*}
1140  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
1141  \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}
1142  \end{equation*}  \end{equation*}
1143  and on substituting into (\ref{eq-p-heat-interim}) gives:  and on substituting into (\ref{eq-p-heat-interim}) gives:
1144  \begin{equation}  \begin{equation}
# Line 1090  and on substituting into (\ref{eq-p-heat Line 1147  and on substituting into (\ref{eq-p-heat
1147  \end{equation}  \end{equation}
1148  which is in conservative form.  which is in conservative form.
1149    
1150  For convenience in the model we prefer to step forward (\ref%  For convenience in the model we prefer to step forward (\ref
1151  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).
1152    
1153  \subsubsection{Boundary conditions}  \subsubsection{Boundary conditions}
# Line 1134  _{o}(p_{o})=g~Z_{topo}$, defined: Line 1191  _{o}(p_{o})=g~Z_{topo}$, defined:
1191    
1192  The final form of the HPE's in p coordinates is then:  The final form of the HPE's in p coordinates is then:
1193  \begin{eqnarray}  \begin{eqnarray}
1194  \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}}
1195  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \label{eq:atmos-prime} \\
1196  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\
1197  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1198  \partial p} &=&0 \\  \partial p} &=&0 \\
1199  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\
1200  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime}  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }
1201  \end{eqnarray}  \end{eqnarray}
1202    
1203  % $Header$  % $Header$
# Line 1154  We review here the method by which the s Line 1211  We review here the method by which the s
1211  HPE's for the ocean written in z-coordinates are obtained. The  HPE's for the ocean written in z-coordinates are obtained. The
1212  non-Boussinesq equations for oceanic motion are:  non-Boussinesq equations for oceanic motion are:
1213  \begin{eqnarray}  \begin{eqnarray}
1214  \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}}
1215  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\
1216  \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}
1217  &=&\epsilon _{nh}\mathcal{F}_{w} \\  &=&\epsilon _{nh}\mathcal{F}_{w} \\
1218  \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}}
1219  _{h}+\frac{\partial w}{\partial z} &=&0 \\  _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\
1220  \rho  &=&\rho (\theta ,S,p) \\  \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\
1221  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\
1222  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt}
1223  \end{eqnarray}%  \label{eq:non-boussinesq}
1224    \end{eqnarray}
1225  These equations permit acoustics modes, inertia-gravity waves,  These equations permit acoustics modes, inertia-gravity waves,
1226  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline
1227  mode. As written, they cannot be integrated forward consistently - if we  mode. As written, they cannot be integrated forward consistently - if we
1228  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
1229  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref%  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref
1230  {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
1231  therefore necessary to manipulate the system as follows. Differentiating the  therefore necessary to manipulate the system as follows. Differentiating the
1232  EOS (equation of state) gives:  EOS (equation of state) gives:
# Line 1181  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp Line 1239  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp
1239  \end{equation}  \end{equation}
1240    
1241  Note that $\frac{\partial \rho }{\partial p}=\frac{1}{c_{s}^{2}}$ is the  Note that $\frac{\partial \rho }{\partial p}=\frac{1}{c_{s}^{2}}$ is the
1242  reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref%  reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref{eq-zns-cont} gives:
 {eq-zns-cont} gives:  
1243  \begin{equation}  \begin{equation}
1244  \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{
1245  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}
1246  \end{equation}  \end{equation}
1247  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 1249  adiabatic motion, dropping the $\frac{D\
1249  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
1250  can be explicitly integrated forward:  can be explicitly integrated forward:
1251  \begin{eqnarray}  \begin{eqnarray}
1252  \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}}
1253  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1254  \label{eq-cns-hmom} \\  \label{eq-cns-hmom} \\
1255  \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}
1256  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\
1257  \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{
1258  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\
1259  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\
1260  \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 1268  wherever it appears in a product (ie. no
1268  `Boussinesq assumption'. The only term that then retains the full variation  `Boussinesq assumption'. The only term that then retains the full variation
1269  in $\rho $ is the gravitational acceleration:  in $\rho $ is the gravitational acceleration:
1270  \begin{eqnarray}  \begin{eqnarray}
1271  \frac{D\vec{\mathbf{v}}_{h}}{Dt}+f\hat{\mathbf{k}}\times \vec{\mathbf{v}}%  \frac{D\vec{\mathbf{v}}_{h}}{Dt}+f\hat{\mathbf{k}}\times \vec{\mathbf{v}}
1272  _{h}+\frac{1}{\rho _{o}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho _{o}}\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1273  \label{eq-zcb-hmom} \\  \label{eq-zcb-hmom} \\
1274  \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}}
1275  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1276  \label{eq-zcb-hydro} \\  \label{eq-zcb-hydro} \\
1277  \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{
1278  \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} \\
1279  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\
1280  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\
1281  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}
1282  \end{eqnarray}  \end{eqnarray}
1283  These equations still retain acoustic modes. But, because the  These equations still retain acoustic modes. But, because the
1284  ``compressible'' terms are linearized, the pressure equation \ref%  ``compressible'' terms are linearized, the pressure equation \ref
1285  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent
1286  term appears as a Helmholtz term in the non-hydrostatic pressure equation).  term appears as a Helmholtz term in the non-hydrostatic pressure equation).
1287  These are the \emph{truly} compressible Boussinesq equations. Note that the  These are the \emph{truly} compressible Boussinesq equations. Note that the
1288  EOS must have the same pressure dependency as the linearized pressure term,  EOS must have the same pressure dependency as the linearized pressure term,
1289  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{%  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{
1290  c_{s}^{2}}$, for consistency.  c_{s}^{2}}$, for consistency.
1291    
1292  \subsubsection{`Anelastic' z-coordinate equations}  \subsubsection{`Anelastic' z-coordinate equations}
1293    
1294  The anelastic approximation filters the acoustic mode by removing the  The anelastic approximation filters the acoustic mode by removing the
1295  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}%  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}
1296  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}%  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}
1297  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between
1298  continuity and EOS. A better solution is to change the dependency on  continuity and EOS. A better solution is to change the dependency on
1299  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
1300  height and a perturbation:  height and a perturbation:
1301  \begin{equation*}  \begin{equation*}
1302  \rho =\rho (\theta ,S,p_{o}(z)+\epsilon _{s}p^{\prime })  \rho =\rho (\theta ,S,p_{o}(z)+\epsilon _{s}p^{\prime })
1303  \end{equation*}  \end{equation*}
1304  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from
1305  differentiating the EOS, the continuity equation then becomes:  differentiating the EOS, the continuity equation then becomes:
1306  \begin{equation*}  \begin{equation*}
1307  \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{
1308  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+%  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+
1309  \frac{\partial w}{\partial z}=0  \frac{\partial w}{\partial z}=0
1310  \end{equation*}  \end{equation*}
1311  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
1312  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},%  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},
1313  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and
1314  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{%  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{
1315  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta
1316  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon
1317  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation
1318  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
1319  anelastic continuity equation:  anelastic continuity equation:
1320  \begin{equation}  \begin{equation}
1321  \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}-
1322  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}
1323  \end{equation}  \end{equation}
1324  A slightly different route leads to the quasi-Boussinesq continuity equation  A slightly different route leads to the quasi-Boussinesq continuity equation
1325  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+%  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+
1326  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }%  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }
1327  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:
1328  \begin{equation}  \begin{equation}
1329  \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{
1330  \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}
1331  \end{equation}  \end{equation}
1332  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 1335  equation if:
1335  \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}}
1336  \end{equation}  \end{equation}
1337  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$
1338  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 $\frac{
1339  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The
1340  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are
1341  then:  then:
1342  \begin{eqnarray}  \begin{eqnarray}
1343  \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}}
1344  _{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}}}
1345  \label{eq-zab-hmom} \\  \label{eq-zab-hmom} \\
1346  \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}}
1347  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1348  \label{eq-zab-hydro} \\  \label{eq-zab-hydro} \\
1349  \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{
1350  \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} \\
1351  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\
1352  \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 1359  Here, the objective is to drop the depth
1359  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
1360  yield the ``truly'' incompressible Boussinesq equations:  yield the ``truly'' incompressible Boussinesq equations:
1361  \begin{eqnarray}  \begin{eqnarray}
1362  \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}}
1363  _{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}}}
1364  \label{eq-ztb-hmom} \\  \label{eq-ztb-hmom} \\
1365  \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}}
1366  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1367  \label{eq-ztb-hydro} \\  \label{eq-ztb-hydro} \\
1368  \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 1381  retain compressibility effects in the de
1381  density thus:  density thus:
1382  \begin{equation*}  \begin{equation*}
1383  \rho =\rho _{o}+\rho ^{\prime }  \rho =\rho _{o}+\rho ^{\prime }
1384  \end{equation*}%  \end{equation*}
1385  We then assert that variations with depth of $\rho _{o}$ are unimportant  We then assert that variations with depth of $\rho _{o}$ are unimportant
1386  while the compressible effects in $\rho ^{\prime }$ are:  while the compressible effects in $\rho ^{\prime }$ are:
1387  \begin{equation*}  \begin{equation*}
1388  \rho _{o}=\rho _{c}  \rho _{o}=\rho _{c}
1389  \end{equation*}%  \end{equation*}
1390  \begin{equation*}  \begin{equation*}
1391  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}
1392  \end{equation*}%  \end{equation*}
1393  This then yields what we can call the semi-compressible Boussinesq  This then yields what we can call the semi-compressible Boussinesq
1394  equations:  equations:
1395  \begin{eqnarray}  \begin{eqnarray}
1396  \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}}
1397  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{%  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{
1398  \mathcal{F}}}  \label{eq:ocean-mom} \\  \mathcal{F}}}  \label{eq:ocean-mom} \\
1399  \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
1400  _{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 1405  _{c}}\frac{\partial p^{\prime }}{\partia
1405  \\  \\
1406  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\
1407  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}
1408  \end{eqnarray}%  \end{eqnarray}
1409  Note that the hydrostatic pressure of the resting fluid, including that  Note that the hydrostatic pressure of the resting fluid, including that
1410  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
1411  dynamics.  dynamics.
# Line 1372  In spherical coordinates, the velocity c Line 1429  In spherical coordinates, the velocity c
1429  and vertical direction respectively, are given by (see Fig.2) :  and vertical direction respectively, are given by (see Fig.2) :
1430    
1431  \begin{equation*}  \begin{equation*}
1432  u=r\cos \phi \frac{D\lambda }{Dt}  u=r\cos \varphi \frac{D\lambda }{Dt}
1433  \end{equation*}  \end{equation*}
1434    
1435  \begin{equation*}  \begin{equation*}
1436  v=r\frac{D\phi }{Dt}\qquad  v=r\frac{D\varphi }{Dt}\qquad
1437  \end{equation*}  \end{equation*}
1438  $\qquad \qquad \qquad \qquad $  $\qquad \qquad \qquad \qquad $
1439    
1440  \begin{equation*}  \begin{equation*}
1441  \dot{r}=\frac{Dr}{Dt}  \dot{r}=\frac{Dr}{Dt}
1442  \end{equation*}  \end{equation*}
1443    
1444  Here $\phi $ is the latitude, $\lambda $ the longitude, $r$ the radial  Here $\varphi $ is the latitude, $\lambda $ the longitude, $r$ the radial
1445  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
1446  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.
1447    
# Line 1392  The `grad' ($\nabla $) and `div' ($\nabl Line 1449  The `grad' ($\nabla $) and `div' ($\nabl
1449  spherical coordinates:  spherical coordinates:
1450    
1451  \begin{equation*}  \begin{equation*}
1452  \nabla \equiv \left( \frac{1}{r\cos \phi }\frac{\partial }{\partial \lambda }%  \nabla \equiv \left( \frac{1}{r\cos \varphi }\frac{\partial }{\partial \lambda }
1453  ,\frac{1}{r}\frac{\partial }{\partial \phi },\frac{\partial }{\partial r}%  ,\frac{1}{r}\frac{\partial }{\partial \varphi },\frac{\partial }{\partial r}
1454  \right)  \right)
1455  \end{equation*}  \end{equation*}
1456    
1457  \begin{equation*}  \begin{equation*}
1458  \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
1459  \lambda }+\frac{\partial }{\partial \phi }\left( v\cos \phi \right) \right\}  \lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\}
1460  +\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}
1461  \end{equation*}  \end{equation*}
1462    
1463  %%%% \end{document}  %tci%\end{document}

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