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 %%%% \begin{document}  
 %%%%  
 %%%% \tableofcontents  
31    
32  \pagebreak  %tci%\tableofcontents
33    
 \part{MITgcm basics}  
34    
35  % Section: Overview  % Section: Overview
36    
# Line 78  MITgcm has a number of novel aspects: Line 54  MITgcm has a number of novel aspects:
54  \begin{itemize}  \begin{itemize}
55  \item it can be used to study both atmospheric and oceanic phenomena; one  \item it can be used to study both atmospheric and oceanic phenomena; one
56  hydrodynamical kernel is used to drive forward both atmospheric and oceanic  hydrodynamical kernel is used to drive forward both atmospheric and oceanic
57  models - see fig.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 129  studies. Line 83  studies.
83  computational platforms.  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.  
88    \begin{verbatim}
89    
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 Eight ECMWF Workshop on the Use of Parallel Processors
123    in Meteorology
124    
125    Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999)
126    Construction of the adjoint MIT ocean general circulation model and
127    application to Atlantic heat transport variability
128    J. Geophysical Res., 104(C12), 29,529-29,547.
129    
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 an estimate of the time-mean
298    surface elevation of the ocean obtained by bringing the model in to
299    consistency with altimetric and in-situ observations over the period
300    1992-1997. {\bf CHANGE THIS TEXT - FIG FROM PATRICK/CARL/DETLEF}
301    
302    %% CNHbegin
303    \input{part1/globes_figure}
304    %% CNHend
305    
306    \subsection{Ocean biogeochemical cycles}
307    
308    MITgcm is being used to study global biogeochemical cycles in the ocean. For
309    example one can study the effects of interannual changes in meteorological
310    forcing and upper ocean circulation on the fluxes of carbon dioxide and
311    oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows
312    the annual air-sea flux of oxygen and its relation to density outcrops in
313    the southern oceans from a single year of a global, interannually varying
314    simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution
315    telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown).
316    
317    %%CNHbegin
318    \input{part1/biogeo_figure}
319    %%CNHend
320    
321    \subsection{Simulations of laboratory experiments}
322    
323    Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a
324    laboratory experiment inquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An
325    initially homogeneous tank of water ($1m$ in diameter) is driven from its
326    free surface by a rotating heated disk. The combined action of mechanical
327    and thermal forcing creates a lens of fluid which becomes baroclinically
328    unstable. The stratification and depth of penetration of the lens is
329    arrested by its instability in a process analogous to that which sets the
330    stratification of the ACC.
331    
332    %%CNHbegin
333    \input{part1/lab_figure}
334    %%CNHend
335    
336  % $Header$  % $Header$
337  % $Name$  % $Name$
# Line 262  Fig.E4 shows.... Line 340  Fig.E4 shows....
340    
341  To render atmosphere and ocean models from one dynamical core we exploit  To render atmosphere and ocean models from one dynamical core we exploit
342  `isomorphisms' between equation sets that govern the evolution of the  `isomorphisms' between equation sets that govern the evolution of the
343  respective fluids - see fig.4%  respective fluids - see figure \ref{fig:isomorphic-equations}.
344  \marginpar{  One system of hydrodynamical equations is written down
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down  
345  and encoded. The model variables have different interpretations depending on  and encoded. The model variables have different interpretations depending on
346  whether the atmosphere or ocean is being studied. Thus, for example, the  whether the atmosphere or ocean is being studied. Thus, for example, the
347  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are
348  modeling the atmosphere and height, $z$, if we are modeling the ocean.  modeling the atmosphere (left hand side of figure \ref{fig:isomorphic-equations})
349    and height, $z$, if we are modeling the ocean (right hand side of figure
350    \ref{fig:isomorphic-equations}).
351    
352    %%CNHbegin
353    \input{part1/zandpcoord_figure.tex}
354    %%CNHend
355    
356  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
357  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 359  velocity $\vec{\mathbf{v}}$, active trac
359  depend on $\theta $, $S$, and $p$. The equations that govern the evolution  depend on $\theta $, $S$, and $p$. The equations that govern the evolution
360  of these fields, obtained by applying the laws of classical mechanics and  of these fields, obtained by applying the laws of classical mechanics and
361  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of
362  a generic vertical coordinate, $r$, see fig.5%  a generic vertical coordinate, $r$, so that the appropriate
363  \marginpar{  kinematic boundary conditions can be applied isomorphically
364  Fig.5 The vertical coordinate of model}:  see figure \ref{fig:zandp-vert-coord}.
365    
366  \begin{figure}  %%CNHbegin
367  \begin{center}  \input{part1/vertcoord_figure.tex}
368  \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*}  
369    
370  \begin{equation*}  \begin{equation*}
371  \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}}
372  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}}}
373  vertical mtm}  \text{ horizontal mtm} \label{eq:horizontal_mtm}
374  \end{equation*}  \end{equation*}
375    
376  \begin{equation}  \begin{equation}
377  \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{
378  \partial r}=0\text{ continuity}  \label{eq:continuous}  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{
379    vertical mtm} \label{eq:vertical_mtm}
380  \end{equation}  \end{equation}
381    
382  \begin{equation*}  \begin{equation}
383  b=b(\theta ,S,r)\text{ equation of state}  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{
384  \end{equation*}  \partial r}=0\text{ continuity}  \label{eq:continuity}
385    \end{equation}
386    
387  \begin{equation*}  \begin{equation}
388  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{  potential temperature}  b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state}
389  \end{equation*}  \end{equation}
390    
391  \begin{equation*}  \begin{equation}
392  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{  humidity/salinity}  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}
393  \end{equation*}  \label{eq:potential_temperature}
394    \end{equation}
395    
396    \begin{equation}
397    \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}
398    \label{eq:humidity_salt}
399    \end{equation}
400    
401  Here:  Here:
402    
403  \begin{equation*}  \begin{equation*}
404  r\text{ is the vertical coordinate}  r\text{ is the vertical coordinate}
405  \end{equation*}  \end{equation*}
406    
407  \begin{equation*}  \begin{equation*}
408  \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{
409  is the total derivative}  is the total derivative}
410  \end{equation*}  \end{equation*}
411    
412  \begin{equation*}  \begin{equation*}
413  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}%  \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}
414  \text{ is the `grad' operator}  \text{ is the `grad' operator}
415  \end{equation*}  \end{equation*}
416  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}%  with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}
417  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$  \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$
418  is a unit vector in the vertical  is a unit vector in the vertical
419    
420  \begin{equation*}  \begin{equation*}
421  t\text{ is time}  t\text{ is time}
422  \end{equation*}  \end{equation*}
423    
424  \begin{equation*}  \begin{equation*}
425  \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
426  velocity}  velocity}
427  \end{equation*}  \end{equation*}
428    
429  \begin{equation*}  \begin{equation*}
430  \phi \text{ is the `pressure'/`geopotential'}  \phi \text{ is the `pressure'/`geopotential'}
431  \end{equation*}  \end{equation*}
432    
433  \begin{equation*}  \begin{equation*}
434  \vec{\Omega}\text{ is the Earth's rotation}  \vec{\Omega}\text{ is the Earth's rotation}
435  \end{equation*}  \end{equation*}
436    
437  \begin{equation*}  \begin{equation*}
438  b\text{ is the `buoyancy'}  b\text{ is the `buoyancy'}
439  \end{equation*}  \end{equation*}
440    
441  \begin{equation*}  \begin{equation*}
442  \theta \text{ is potential temperature}  \theta \text{ is potential temperature}
443  \end{equation*}  \end{equation*}
444    
445  \begin{equation*}  \begin{equation*}
446  S\text{ is specific humidity in the atmosphere; salinity in the ocean}  S\text{ is specific humidity in the atmosphere; salinity in the ocean}
447  \end{equation*}  \end{equation*}
448    
449  \begin{equation*}  \begin{equation*}
450  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{%  \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{
451  \mathbf{v}}  \mathbf{v}}
452  \end{equation*}  \end{equation*}
453    
454  \begin{equation*}  \begin{equation*}
455  \mathcal{Q}_{\theta }\mathcal{\ }\text{are forcing and dissipation of }%  \mathcal{Q}_{\theta }\mathcal{\ }\text{are forcing and dissipation of }\theta
 \theta  
456  \end{equation*}  \end{equation*}
457    
458  \begin{equation*}  \begin{equation*}
# Line 385  S\text{ is specific humidity in the atmo Line 460  S\text{ is specific humidity in the atmo
460  \end{equation*}  \end{equation*}
461    
462  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
463  extensive `physics' packages for atmosphere and ocean described in Chapter 6.  `physics' and forcing packages for atmosphere and ocean. These are described
464    in later chapters.
465    
466  \subsection{Kinematic Boundary conditions}  \subsection{Kinematic Boundary conditions}
467    
468  \subsubsection{vertical}  \subsubsection{vertical}
469    
470  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}):
471    
472  \begin{equation}  \begin{equation}
473  \dot{r}=0atr=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)}  \dot{r}=0atr=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)}
# Line 400  at fixed and moving $r$ surfaces we set Line 476  at fixed and moving $r$ surfaces we set
476    
477  \begin{equation}  \begin{equation}
478  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \
479  (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc}  (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc}
480  \end{equation}  \end{equation}
481    
482  Here  Here
483    
484  \begin{equation*}  \begin{equation*}
485  R_{moving}=R_{o}+\eta  R_{moving}=R_{o}+\eta
486  \end{equation*}  \end{equation*}
487  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
488  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 493  of motion.
493    
494  \begin{equation}  \begin{equation}
495  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}  \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow}
496  \end{equation}%  \end{equation}
497  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.  where $\vec{\mathbf{n}}$ is the normal to a solid boundary.
498    
499  \subsection{Atmosphere}  \subsection{Atmosphere}
500    
501  In the atmosphere, see fig.5, we interpret:  In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret:
502    
503  \begin{equation}  \begin{equation}
504  r=p\text{ is the pressure}  \label{eq:atmos-r}  r=p\text{ is the pressure}  \label{eq:atmos-r}
# Line 454  where Line 530  where
530    
531  \begin{equation*}  \begin{equation*}
532  T\text{ is absolute temperature}  T\text{ is absolute temperature}
533  \end{equation*}%  \end{equation*}
534  \begin{equation*}  \begin{equation*}
535  p\text{ is the pressure}  p\text{ is the pressure}
536  \end{equation*}%  \end{equation*}
537  \begin{eqnarray*}  \begin{eqnarray*}
538  &&z\text{ is the height of the pressure surface} \\  &&z\text{ is the height of the pressure surface} \\
539  &&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 543  In the above the ideal gas law, $p=\rho
543  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)
544  \begin{equation}  \begin{equation}
545  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner}
546  \end{equation}%  \end{equation}
547  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
548  constant and $c_{p}$ the specific heat of air at constant pressure.  constant and $c_{p}$ the specific heat of air at constant pressure.
549    
550  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):
551    
552  \begin{equation*}  \begin{equation*}
553  R_{fixed}=p_{top}=0  R_{fixed}=p_{top}=0
554  \end{equation*}  \end{equation*}
555  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
556  given by  given by
557  \begin{equation*}  \begin{equation*}
558  R_{moving}=R_{o}(x,y)=p_{o}(x,y)  R_{moving}=R_{o}(x,y)=p_{o}(x,y)
559  \end{equation*}  \end{equation*}
560  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
561  atmosphere.  atmosphere.
# Line 493  The boundary conditions at top and botto Line 569  The boundary conditions at top and botto
569  atmosphere)}  \label{eq:moving-bc-atmos}  atmosphere)}  \label{eq:moving-bc-atmos}
570  \end{eqnarray}  \end{eqnarray}
571    
572  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})
573  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 $p$
574  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).
575    
576  \subsection{Ocean}  \subsection{Ocean}
# Line 517  At the bottom of the ocean: $R_{fixed}(x Line 593  At the bottom of the ocean: $R_{fixed}(x
593    
594  The surface of the ocean is given by: $R_{moving}=\eta $  The surface of the ocean is given by: $R_{moving}=\eta $
595    
596  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 $
597  R_{o}=Z_{o}=0$.  R_{o}=Z_{o}=0$.
598    
599  Boundary conditions are:  Boundary conditions are:
# Line 525  Boundary conditions are: Line 601  Boundary conditions are:
601  \begin{eqnarray}  \begin{eqnarray}
602  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}
603  \\  \\
604  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)
605  \label{eq:moving-bc-ocean}}  \label{eq:moving-bc-ocean}}
606  \end{eqnarray}  \end{eqnarray}
607  where $\eta $ is the elevation of the free surface.  where $\eta $ is the elevation of the free surface.
608    
609  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
610    of oceanic equations
611  which, for convenience, are written out in $z$ coordinates in Appendix Ocean  which, for convenience, are written out in $z$ coordinates in Appendix Ocean
612  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).
613    
# Line 542  Let us separate $\phi $ in to surface, h Line 619  Let us separate $\phi $ in to surface, h
619  \begin{equation}  \begin{equation}
620  \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)
621  \label{eq:phi-split}  \label{eq:phi-split}
622  \end{equation}%  \end{equation}
623  and write eq(\ref{incompressible}a,b) in the form:  and write eq(\ref{eq:incompressible}) in the form:
624    
625  \begin{equation}  \begin{equation}
626  \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 633  _{nh}=\vec{\mathbf{G}}_{\vec{v}_{h}}  \l
633  \end{equation}  \end{equation}
634    
635  \begin{equation}  \begin{equation}
636  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{%  \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{
637  \partial r}=G_{\dot{r}}  \label{eq:mom-w}  \partial r}=G_{\dot{r}}  \label{eq:mom-w}
638  \end{equation}  \end{equation}
639  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.  Here $\epsilon _{nh}$ is a non-hydrostatic parameter.
640    
641  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
642  {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
643  terms in the momentum equations. In spherical coordinates they take the form%  terms in the momentum equations. In spherical coordinates they take the form
644  \footnote{%  \footnote{
645  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms  In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms
646  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref%  in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref
647  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in  {eq:gw-spherical}) are omitted; the singly-underlined terms are included in
648  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (%  the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (
649  \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
650  discussion:  discussion:
651    
# Line 576  discussion: Line 653  discussion:
653  \left.  \left.
654  \begin{tabular}{l}  \begin{tabular}{l}
655  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\
656  $-\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\} $
657  \\  \\
658  $-\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\} $
659  \\  \\
660  $+\mathcal{F}_{u}$%  $+\mathcal{F}_{u}$
661  \end{tabular}%  \end{tabular}
662  \ \right\} \left\{  \ \right\} \left\{
663  \begin{tabular}{l}  \begin{tabular}{l}
664  \textit{advection} \\  \textit{advection} \\
665  \textit{metric} \\  \textit{metric} \\
666  \textit{Coriolis} \\  \textit{Coriolis} \\
667  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
668  \end{tabular}%  \end{tabular}
669  \ \right. \qquad   \label{eq:gu-speherical}  \ \right. \qquad  \label{eq:gu-speherical}
670  \end{equation}  \end{equation}
671    
672  \begin{equation}  \begin{equation}
673  \left.  \left.
674  \begin{tabular}{l}  \begin{tabular}{l}
675  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\
676  $-\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\}
677  $ \\  $ \\
678  $-\left\{ -2\Omega u\sin lat\right\} $ \\  $-\left\{ -2\Omega u\sin \varphi \right\} $ \\
679  $+\mathcal{F}_{v}$%  $+\mathcal{F}_{v}$
680  \end{tabular}%  \end{tabular}
681  \ \right\} \left\{  \ \right\} \left\{
682  \begin{tabular}{l}  \begin{tabular}{l}
683  \textit{advection} \\  \textit{advection} \\
684  \textit{metric} \\  \textit{metric} \\
685  \textit{Coriolis} \\  \textit{Coriolis} \\
686  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
687  \end{tabular}%  \end{tabular}
688  \ \right. \qquad   \label{eq:gv-spherical}  \ \right. \qquad  \label{eq:gv-spherical}
689  \end{equation}%  \end{equation}
690  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
691    
692  \begin{equation}  \begin{equation}
693  \left.  \left.
694  \begin{tabular}{l}  \begin{tabular}{l}
695  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\
696  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\
697  ${+}\underline{{2\Omega u\cos lat}}$ \\  ${+}\underline{{2\Omega u\cos \varphi}}$ \\
698  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$%  $\underline{\underline{\mathcal{F}_{\dot{r}}}}$
699  \end{tabular}%  \end{tabular}
700  \ \right\} \left\{  \ \right\} \left\{
701  \begin{tabular}{l}  \begin{tabular}{l}
702  \textit{advection} \\  \textit{advection} \\
703  \textit{metric} \\  \textit{metric} \\
704  \textit{Coriolis} \\  \textit{Coriolis} \\
705  \textit{\ Forcing/Dissipation}%  \textit{\ Forcing/Dissipation}
706  \end{tabular}%  \end{tabular}
707  \ \right.   \label{eq:gw-spherical}  \ \right.  \label{eq:gw-spherical}
708  \end{equation}%  \end{equation}
709  \qquad \qquad \qquad \qquad \qquad  \qquad \qquad \qquad \qquad \qquad
710    
711  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 `$\varphi$
712  ' is latitude.  ' is latitude.
713    
714  Grad and div operators in spherical coordinates are defined in appendix  Grad and div operators in spherical coordinates are defined in appendix
715  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}  
716    
717    %%CNHbegin
718    \input{part1/sphere_coord_figure.tex}
719    %%CNHend
720    
721  \subsubsection{Shallow atmosphere approximation}  \subsubsection{Shallow atmosphere approximation}
722    
# Line 661  hydrostatic balance and the `traditional Line 726  hydrostatic balance and the `traditional
726  Coriolis force is treated approximately and the shallow atmosphere  Coriolis force is treated approximately and the shallow atmosphere
727  approximation is made.\ The MITgcm need not make the `traditional  approximation is made.\ The MITgcm need not make the `traditional
728  approximation'. To be able to support consistent non-hydrostatic forms the  approximation'. To be able to support consistent non-hydrostatic forms the
729  shallow atmosphere approximation can be relaxed - when dividing through by $r  shallow atmosphere approximation can be relaxed - when dividing through by $
730  $ 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 $a$,
731  the radius of the earth.  the radius of the earth.
732    
733  \subsubsection{Hydrostatic and quasi-hydrostatic forms}  \subsubsection{Hydrostatic and quasi-hydrostatic forms}
734    \label{sec:hydrostatic_and_quasi-hydrostatic_forms}
735    
736  These are discussed at length in Marshall et al (1997a).  These are discussed at length in Marshall et al (1997a).
737    
# Line 674  terms in Eqs. (\ref{eq:gu-speherical} $\ Line 740  terms in Eqs. (\ref{eq:gu-speherical} $\
740  are neglected and `${r}$' is replaced by `$a$', the mean radius of the  are neglected and `${r}$' is replaced by `$a$', the mean radius of the
741  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
742  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
743  computed at all other levels by integration of the hydrostatic relation, eq(%  computed at all other levels by integration of the hydrostatic relation, eq(
744  \ref{eq:hydrostatic}).  \ref{eq:hydrostatic}).
745    
746  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between  In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between
747  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
748  \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
749  contribution to the pressure field: only the terms underlined twice in Eqs. (%  contribution to the pressure field: only the terms underlined twice in Eqs. (
750  \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
751  and, simultaneously, the shallow atmosphere approximation is relaxed. In  and, simultaneously, the shallow atmosphere approximation is relaxed. In
752  \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 754  variation of the radial position of a pa
754  vertical momentum equation (\ref{eq:mom-w}) becomes:  vertical momentum equation (\ref{eq:mom-w}) becomes:
755    
756  \begin{equation*}  \begin{equation*}
757  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos lat  \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos \varphi
758  \end{equation*}  \end{equation*}
759  making a small correction to the hydrostatic pressure.  making a small correction to the hydrostatic pressure.
760    
# Line 704  only a quasi-non-hydrostatic atmospheric Line 770  only a quasi-non-hydrostatic atmospheric
770    
771  \paragraph{Non-hydrostatic Ocean}  \paragraph{Non-hydrostatic Ocean}
772    
773  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref%  In the non-hydrostatic ocean model all terms in equations Eqs.(\ref
774  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A  {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A
775  three dimensional elliptic equation must be solved subject to Neumann  three dimensional elliptic equation must be solved subject to Neumann
776  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
777  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
778  incompressible condition eq(\ref{eq:continuous})c has already filtered out  incompressible condition eq(\ref{eq:continuity}) has already filtered out
779  acoustic modes. It does, however, ensure that the gravity waves are treated  acoustic modes. It does, however, ensure that the gravity waves are treated
780  accurately with an exact dispersion relation. The \textbf{NH} set has a  accurately with an exact dispersion relation. The \textbf{NH} set has a
781  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 783  and Bromley, 1995; Marshall et.al.\ 1997
783    
784  \paragraph{Quasi-nonhydrostatic Atmosphere}  \paragraph{Quasi-nonhydrostatic Atmosphere}
785    
786  In the non-hydrostatic version of our atmospheric model we approximate $\dot{%  In the non-hydrostatic version of our atmospheric model we approximate $\dot{
787  r}$ 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})
788  (but only here) by:  (but only here) by:
789    
790  \begin{equation}  \begin{equation}
791  \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}
792  \end{equation}%  \end{equation}
793  where $p_{hy}$ is the hydrostatic pressure.  where $p_{hy}$ is the hydrostatic pressure.
794    
795  \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 817  equations in $z-$coordinates are support
817    
818  \subparagraph{Non-hydrostatic}  \subparagraph{Non-hydrostatic}
819    
820  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$%  Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$
821  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref%  coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref
822  {eq:ocean-salt}).  {eq:ocean-salt}).
823    
824  \subsection{Solution strategy}  \subsection{Solution strategy}
825    
826  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{
827  NH} models is summarized in Fig.7.%  NH} models is summarized in Figure \ref{fig:solution-strategy}.
828  \marginpar{  Under all dynamics, a 2-d elliptic equation is
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is  
829  first solved to find the surface pressure and the hydrostatic pressure at  first solved to find the surface pressure and the hydrostatic pressure at
830  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
831  \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 834  forward and $\dot{r}$ found from continu
834  stepping forward the horizontal momentum equations; $\dot{r}$ is found by  stepping forward the horizontal momentum equations; $\dot{r}$ is found by
835  stepping forward the vertical momentum equation.  stepping forward the vertical momentum equation.
836    
837  \begin{figure}  %%CNHbegin
838  \begin{center}  \input{part1/solution_strategy_figure.tex}
839  \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}  
   
840    
841  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
842  course, some complication that goes with the inclusion of $\cos \phi \ $%  course, some complication that goes with the inclusion of $\cos \varphi \ $
843  Coriolis terms and the relaxation of the shallow atmosphere approximation.  Coriolis terms and the relaxation of the shallow atmosphere approximation.
844  But this leads to negligible increase in computation. In \textbf{NH}, in  But this leads to negligible increase in computation. In \textbf{NH}, in
845  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 849  Marshall et al, 1997) resulting in a non
849  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.
850    
851  \subsection{Finding the pressure field}  \subsection{Finding the pressure field}
852    \label{sec:finding_the_pressure_field}
853    
854  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the
855  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 864  Hydrostatic pressure is obtained by inte
864  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:
865    
866  \begin{equation*}  \begin{equation*}
867  \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}
868  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr  \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr
869  \end{equation*}  \end{equation*}
870  and so  and so
871    
# Line 826  atmospheric pressure pushing down on the Line 882  atmospheric pressure pushing down on the
882    
883  \subsubsection{Surface pressure}  \subsubsection{Surface pressure}
884    
885  The surface pressure equation can be obtained by integrating continuity, (%  The surface pressure equation can be obtained by integrating continuity,
886  \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$  (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$
887    
888  \begin{equation*}  \begin{equation*}
889  \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}
890  }_{h}+\partial _{r}\dot{r}\right) dr=0  }_{h}+\partial _{r}\dot{r}\right) dr=0
891  \end{equation*}  \end{equation*}
892    
893  Thus:  Thus:
894    
895  \begin{equation*}  \begin{equation*}
896  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta  \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta
897  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}%  +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}
898  _{h}dr=0  _{h}dr=0
899  \end{equation*}  \end{equation*}
900  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 $
901  r $. The above can be rearranged to yield, using Leibnitz's theorem:  r $. The above can be rearranged to yield, using Leibnitz's theorem:
902    
903  \begin{equation}  \begin{equation}
904  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot  \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot
905  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}  \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source}
906  \label{eq:free-surface}  \label{eq:free-surface}
907  \end{equation}%  \end{equation}
908  where we have incorporated a source term.  where we have incorporated a source term.
909    
910  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential
911  (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can  (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can
912  be written  be written
913  \begin{equation}  \begin{equation}
914  \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)
915  \label{eq:phi-surf}  \label{eq:phi-surf}
916  \end{equation}%  \end{equation}
917  where $b_{s}$ is the buoyancy at the surface.  where $b_{s}$ is the buoyancy at the surface.
918    
919  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
920  {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
921  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free
922  surface' and `rigid lid' approaches are available.  surface' and `rigid lid' approaches are available.
923    
924  \subsubsection{Non-hydrostatic pressure}  \subsubsection{Non-hydrostatic pressure}
925    
926  Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{%  Taking the horizontal divergence of (\ref{eq:mom-h}) and adding
927  \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation  $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation
928  (\ref{incompressible}), we deduce that:  (\ref{eq:continuity}), we deduce that:
929    
930  \begin{equation}  \begin{equation}
931  \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{
932  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .%  \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .
933  \vec{\mathbf{F}}  \label{eq:3d-invert}  \vec{\mathbf{F}}  \label{eq:3d-invert}
934  \end{equation}  \end{equation}
935    
# Line 893  coasts (in the ocean) and the bottom: Line 949  coasts (in the ocean) and the bottom:
949  \end{equation}  \end{equation}
950  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
951  kinematic condition (\ref{nonormalflow}) is also applied to the vertical  kinematic condition (\ref{nonormalflow}) is also applied to the vertical
952  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 $
953  \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
954  tangential component of velocity, $v_{T}$, at all solid boundaries,  tangential component of velocity, $v_{T}$, at all solid boundaries,
955  depending on the form chosen for the dissipative terms in the momentum  depending on the form chosen for the dissipative terms in the momentum
956  equations - see below.  equations - see below.
957    
958  Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that:  Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that:
959    
960  \begin{equation}  \begin{equation}
961  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}
# Line 910  where Line 966  where
966  \begin{equation*}  \begin{equation*}
967  \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
968  _{s}+\mathbf{\nabla }\phi _{hyd}\right)  _{s}+\mathbf{\nabla }\phi _{hyd}\right)
969  \end{equation*}%  \end{equation*}
970  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem  presenting inhomogeneous Neumann boundary conditions to the Elliptic problem
971  (\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
972  exploit classical 3D potential theory and, by introducing an appropriately  exploit classical 3D potential theory and, by introducing an appropriately
973  chosen $\delta $-function sheet of `source-charge', replace the inhomogenous  chosen $\delta $-function sheet of `source-charge', replace the
974  boundary condition on pressure by a homogeneous one. The source term $rhs$  inhomogeneous boundary condition on pressure by a homogeneous one. The
975  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 $
976  By simultaneously setting $%  \vec{\mathbf{F}}.$ By simultaneously setting $
977  \begin{array}{l}  \begin{array}{l}
978  \widehat{n}.\vec{\mathbf{F}}%  \widehat{n}.\vec{\mathbf{F}}
979  \end{array}%  \end{array}
980  =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
981  self-consistent but simpler homogenised Elliptic problem is obtained:  self-consistent but simpler homogenized Elliptic problem is obtained:
982    
983  \begin{equation*}  \begin{equation*}
984  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad  \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad
985  \end{equation*}%  \end{equation*}
986  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such  where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such
987  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
988  {eq:inhom-neumann-nh}) the modified boundary condition becomes:  {eq:inhom-neumann-nh}) the modified boundary condition becomes:
989    
990  \begin{equation}  \begin{equation}
# Line 939  If the flow is `close' to hydrostatic ba Line 995  If the flow is `close' to hydrostatic ba
995  converges rapidly because $\phi _{nh}\ $is then only a small correction to  converges rapidly because $\phi _{nh}\ $is then only a small correction to
996  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).
997    
998  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})
999  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.
1000    
1001  \subsection{Forcing/dissipation}  \subsection{Forcing/dissipation}
# Line 947  does not vanish at $r=R_{moving}$, and s Line 1003  does not vanish at $r=R_{moving}$, and s
1003  \subsubsection{Forcing}  \subsubsection{Forcing}
1004    
1005  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
1006  `physics packages' described in detail in chapter ??.  `physics packages' and forcing packages. These are described later on.
1007    
1008  \subsubsection{Dissipation}  \subsubsection{Dissipation}
1009    
# Line 957  Many forms of momentum dissipation are a Line 1013  Many forms of momentum dissipation are a
1013  biharmonic frictions are commonly used:  biharmonic frictions are commonly used:
1014    
1015  \begin{equation}  \begin{equation}
1016  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}}
1017  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}  +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation}
1018  \end{equation}  \end{equation}
1019  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 1024  friction. These coefficients are the sam
1024    
1025  The mixing terms for the temperature and salinity equations have a similar  The mixing terms for the temperature and salinity equations have a similar
1026  form to that of momentum except that the diffusion tensor can be  form to that of momentum except that the diffusion tensor can be
1027  non-diagonal and have varying coefficients. $\qquad $%  non-diagonal and have varying coefficients. $\qquad $
1028  \begin{equation}  \begin{equation}
1029  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
1030  _{h}^{4}(T,S)  \label{eq:diffusion}  _{h}^{4}(T,S)  \label{eq:diffusion}
1031  \end{equation}  \end{equation}
1032  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $%  where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $
1033  horizontal coefficient for biharmonic diffusion. In the simplest case where  horizontal coefficient for biharmonic diffusion. In the simplest case where
1034  the subgrid-scale fluxes of heat and salt are parameterized with constant  the subgrid-scale fluxes of heat and salt are parameterized with constant
1035  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 1040  reduces to a diagonal matrix with consta
1040  \begin{array}{ccc}  \begin{array}{ccc}
1041  K_{h} & 0 & 0 \\  K_{h} & 0 & 0 \\
1042  0 & K_{h} & 0 \\  0 & K_{h} & 0 \\
1043  0 & 0 & K_{v}%  0 & 0 & K_{v}
1044  \end{array}  \end{array}
1045  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}  \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor}
1046  \end{equation}  \end{equation}
# Line 994  salinity ... ). Line 1050  salinity ... ).
1050    
1051  \subsection{Vector invariant form}  \subsection{Vector invariant form}
1052    
1053  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
1054  {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:
1055    
1056  \begin{equation}  \begin{equation}
1057  \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}
1058  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla %  +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla
1059  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]  \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right]
1060  \label{eq:vi-identity}  \label{eq:vi-identity}
1061  \end{equation}%  \end{equation}
1062  This permits alternative numerical treatments of the non-linear terms based  This permits alternative numerical treatments of the non-linear terms based
1063  on their representation as a vorticity flux. Because gradients of coordinate  on their representation as a vorticity flux. Because gradients of coordinate
1064  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
1065  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref%  representation of the metric terms in (\ref{eq:gu-speherical}), (\ref
1066  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information  {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information
1067  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
1068  to discretize the model.  to discretize the model.
1069    
1070  \subsection{Adjoint}  \subsection{Adjoint}
1071    
1072  Tangent linear and adoint counterparts of the forward model and described in  Tangent linear and adjoint counterparts of the forward model are described
1073  Chapter 5.  in Chapter 5.
1074    
1075  % $Header$  % $Header$
1076  % $Name$  % $Name$
# Line 1028  coordinates} Line 1084  coordinates}
1084    
1085  The hydrostatic primitive equations (HPEs) in p-coordinates are:  The hydrostatic primitive equations (HPEs) in p-coordinates are:
1086  \begin{eqnarray}  \begin{eqnarray}
1087  \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}}
1088  _{h}+\mathbf{\nabla }_{p}\phi  &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}}
1089  \label{eq:atmos-mom} \\  \label{eq:atmos-mom} \\
1090  \frac{\partial \phi }{\partial p}+\alpha  &=&0  \label{eq-p-hydro-start} \\  \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\
1091  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1092  \partial p} &=&0  \label{eq:atmos-cont} \\  \partial p} &=&0  \label{eq:atmos-cont} \\
1093  p\alpha  &=&RT  \label{eq:atmos-eos} \\  p\alpha &=&RT  \label{eq:atmos-eos} \\
1094  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}
1095  \end{eqnarray}%  \end{eqnarray}
1096  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
1097  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot
1098  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total  \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total
1099  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
1100  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp%  the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp
1101  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref%  }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref
1102  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $%  {eq:atmos-heat}) is the first law of thermodynamics where internal energy $
1103  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 $
1104  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.
1105    
1106  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 1108  $\theta $ so that it looks more like a g
1108  Differentiating (\ref{eq:atmos-eos}) we get:  Differentiating (\ref{eq:atmos-eos}) we get:
1109  \begin{equation*}  \begin{equation*}
1110  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}
1111  \end{equation*}%  \end{equation*}
1112  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 $
1113  c_{p}=c_{v}+R$, gives:  c_{p}=c_{v}+R$, gives:
1114  \begin{equation}  \begin{equation}
1115  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}  c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q}
1116  \label{eq-p-heat-interim}  \label{eq-p-heat-interim}
1117  \end{equation}%  \end{equation}
1118  Potential temperature is defined:  Potential temperature is defined:
1119  \begin{equation}  \begin{equation}
1120  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}  \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp}
1121  \end{equation}%  \end{equation}
1122  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
1123  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:
1124  \begin{equation}  \begin{equation}
1125  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}  \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner}
1126  \end{equation}%  \end{equation}
1127  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
1128  the Exner function:  the Exner function:
1129  \begin{equation*}  \begin{equation*}
1130  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
1131  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{%  }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{
1132  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}%  \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}
1133  \frac{Dp}{Dt}  \frac{Dp}{Dt}
1134  \end{equation*}%  \end{equation*}
1135  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.  where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy.
1136    
1137  The heat equation is obtained by noting that  The heat equation is obtained by noting that
1138  \begin{equation*}  \begin{equation*}
1139  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
1140  \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}
1141  \end{equation*}  \end{equation*}
1142  and on substituting into (\ref{eq-p-heat-interim}) gives:  and on substituting into (\ref{eq-p-heat-interim}) gives:
1143  \begin{equation}  \begin{equation}
# Line 1090  and on substituting into (\ref{eq-p-heat Line 1146  and on substituting into (\ref{eq-p-heat
1146  \end{equation}  \end{equation}
1147  which is in conservative form.  which is in conservative form.
1148    
1149  For convenience in the model we prefer to step forward (\ref%  For convenience in the model we prefer to step forward (\ref
1150  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).  {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}).
1151    
1152  \subsubsection{Boundary conditions}  \subsubsection{Boundary conditions}
# Line 1134  _{o}(p_{o})=g~Z_{topo}$, defined: Line 1190  _{o}(p_{o})=g~Z_{topo}$, defined:
1190    
1191  The final form of the HPE's in p coordinates is then:  The final form of the HPE's in p coordinates is then:
1192  \begin{eqnarray}  \begin{eqnarray}
1193  \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}}
1194  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \label{eq:atmos-prime} \\
1195  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\
1196  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{%  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1197  \partial p} &=&0 \\  \partial p} &=&0 \\
1198  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\
1199  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime}  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }
1200  \end{eqnarray}  \end{eqnarray}
1201    
1202  % $Header$  % $Header$
# Line 1154  We review here the method by which the s Line 1210  We review here the method by which the s
1210  HPE's for the ocean written in z-coordinates are obtained. The  HPE's for the ocean written in z-coordinates are obtained. The
1211  non-Boussinesq equations for oceanic motion are:  non-Boussinesq equations for oceanic motion are:
1212  \begin{eqnarray}  \begin{eqnarray}
1213  \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}}
1214  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\
1215  \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}
1216  &=&\epsilon _{nh}\mathcal{F}_{w} \\  &=&\epsilon _{nh}\mathcal{F}_{w} \\
1217  \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}}
1218  _{h}+\frac{\partial w}{\partial z} &=&0 \\  _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\
1219  \rho  &=&\rho (\theta ,S,p) \\  \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\
1220  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\
1221  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt}
1222  \end{eqnarray}%  \label{eq:non-boussinesq}
1223    \end{eqnarray}
1224  These equations permit acoustics modes, inertia-gravity waves,  These equations permit acoustics modes, inertia-gravity waves,
1225  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline
1226  mode. As written, they cannot be integrated forward consistently - if we  mode. As written, they cannot be integrated forward consistently - if we
1227  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
1228  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref%  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref
1229  {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
1230  therefore necessary to manipulate the system as follows. Differentiating the  therefore necessary to manipulate the system as follows. Differentiating the
1231  EOS (equation of state) gives:  EOS (equation of state) gives:
# Line 1181  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp Line 1238  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp
1238  \end{equation}  \end{equation}
1239    
1240  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
1241  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:  
1242  \begin{equation}  \begin{equation}
1243  \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{
1244  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}
1245  \end{equation}  \end{equation}
1246  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 1248  adiabatic motion, dropping the $\frac{D\
1248  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
1249  can be explicitly integrated forward:  can be explicitly integrated forward:
1250  \begin{eqnarray}  \begin{eqnarray}
1251  \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}}
1252  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}}
1253  \label{eq-cns-hmom} \\  \label{eq-cns-hmom} \\
1254  \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}
1255  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\  &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\
1256  \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{
1257  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\  v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\
1258  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\
1259  \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 1267  wherever it appears in a product (ie. no
1267  `Boussinesq assumption'. The only term that then retains the full variation  `Boussinesq assumption'. The only term that then retains the full variation
1268  in $\rho $ is the gravitational acceleration:  in $\rho $ is the gravitational acceleration:
1269  \begin{eqnarray}  \begin{eqnarray}
1270  \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}}
1271  _{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}}}
1272  \label{eq-zcb-hmom} \\  \label{eq-zcb-hmom} \\
1273  \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}}
1274  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1275  \label{eq-zcb-hydro} \\  \label{eq-zcb-hydro} \\
1276  \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{
1277  \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} \\
1278  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\  \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\
1279  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\
1280  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt}
1281  \end{eqnarray}  \end{eqnarray}
1282  These equations still retain acoustic modes. But, because the  These equations still retain acoustic modes. But, because the
1283  ``compressible'' terms are linearized, the pressure equation \ref%  ``compressible'' terms are linearized, the pressure equation \ref
1284  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent  {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent
1285  term appears as a Helmholtz term in the non-hydrostatic pressure equation).  term appears as a Helmholtz term in the non-hydrostatic pressure equation).
1286  These are the \emph{truly} compressible Boussinesq equations. Note that the  These are the \emph{truly} compressible Boussinesq equations. Note that the
1287  EOS must have the same pressure dependency as the linearized pressure term,  EOS must have the same pressure dependency as the linearized pressure term,
1288  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{%  ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{
1289  c_{s}^{2}}$, for consistency.  c_{s}^{2}}$, for consistency.
1290    
1291  \subsubsection{`Anelastic' z-coordinate equations}  \subsubsection{`Anelastic' z-coordinate equations}
1292    
1293  The anelastic approximation filters the acoustic mode by removing the  The anelastic approximation filters the acoustic mode by removing the
1294  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}%  time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}
1295  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}%  ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}
1296  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between  \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between
1297  continuity and EOS. A better solution is to change the dependency on  continuity and EOS. A better solution is to change the dependency on
1298  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
1299  height and a perturbation:  height and a perturbation:
1300  \begin{equation*}  \begin{equation*}
1301  \rho =\rho (\theta ,S,p_{o}(z)+\epsilon _{s}p^{\prime })  \rho =\rho (\theta ,S,p_{o}(z)+\epsilon _{s}p^{\prime })
1302  \end{equation*}  \end{equation*}
1303  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from  Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from
1304  differentiating the EOS, the continuity equation then becomes:  differentiating the EOS, the continuity equation then becomes:
1305  \begin{equation*}  \begin{equation*}
1306  \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{
1307  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+%  Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+
1308  \frac{\partial w}{\partial z}=0  \frac{\partial w}{\partial z}=0
1309  \end{equation*}  \end{equation*}
1310  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
1311  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},%  those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},
1312  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and
1313  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{%  $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{
1314  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta  Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta
1315  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon  ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon
1316  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation  _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation
1317  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
1318  anelastic continuity equation:  anelastic continuity equation:
1319  \begin{equation}  \begin{equation}
1320  \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}-
1321  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}  \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1}
1322  \end{equation}  \end{equation}
1323  A slightly different route leads to the quasi-Boussinesq continuity equation  A slightly different route leads to the quasi-Boussinesq continuity equation
1324  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+%  where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+
1325  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }%  \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }
1326  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:
1327  \begin{equation}  \begin{equation}
1328  \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{
1329  \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}
1330  \end{equation}  \end{equation}
1331  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 1334  equation if:
1334  \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}}
1335  \end{equation}  \end{equation}
1336  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$  Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$
1337  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 $\frac{
1338  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The  g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The
1339  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are  full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are
1340  then:  then:
1341  \begin{eqnarray}  \begin{eqnarray}
1342  \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}}
1343  _{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}}}
1344  \label{eq-zab-hmom} \\  \label{eq-zab-hmom} \\
1345  \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}}
1346  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1347  \label{eq-zab-hydro} \\  \label{eq-zab-hydro} \\
1348  \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{
1349  \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} \\
1350  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\  \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\
1351  \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 1358  Here, the objective is to drop the depth
1358  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
1359  yield the ``truly'' incompressible Boussinesq equations:  yield the ``truly'' incompressible Boussinesq equations:
1360  \begin{eqnarray}  \begin{eqnarray}
1361  \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}}
1362  _{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}}}
1363  \label{eq-ztb-hmom} \\  \label{eq-ztb-hmom} \\
1364  \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}}
1365  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}  \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w}
1366  \label{eq-ztb-hydro} \\  \label{eq-ztb-hydro} \\
1367  \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 1380  retain compressibility effects in the de
1380  density thus:  density thus:
1381  \begin{equation*}  \begin{equation*}
1382  \rho =\rho _{o}+\rho ^{\prime }  \rho =\rho _{o}+\rho ^{\prime }
1383  \end{equation*}%  \end{equation*}
1384  We then assert that variations with depth of $\rho _{o}$ are unimportant  We then assert that variations with depth of $\rho _{o}$ are unimportant
1385  while the compressible effects in $\rho ^{\prime }$ are:  while the compressible effects in $\rho ^{\prime }$ are:
1386  \begin{equation*}  \begin{equation*}
1387  \rho _{o}=\rho _{c}  \rho _{o}=\rho _{c}
1388  \end{equation*}%  \end{equation*}
1389  \begin{equation*}  \begin{equation*}
1390  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}  \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o}
1391  \end{equation*}%  \end{equation*}
1392  This then yields what we can call the semi-compressible Boussinesq  This then yields what we can call the semi-compressible Boussinesq
1393  equations:  equations:
1394  \begin{eqnarray}  \begin{eqnarray}
1395  \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}}
1396  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{%  _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{
1397  \mathcal{F}}}  \label{eq:ocean-mom} \\  \mathcal{F}}}  \label{eq:ocean-mom} \\
1398  \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
1399  _{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 1404  _{c}}\frac{\partial p^{\prime }}{\partia
1404  \\  \\
1405  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\
1406  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt}
1407  \end{eqnarray}%  \end{eqnarray}
1408  Note that the hydrostatic pressure of the resting fluid, including that  Note that the hydrostatic pressure of the resting fluid, including that
1409  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
1410  dynamics.  dynamics.
# Line 1372  In spherical coordinates, the velocity c Line 1428  In spherical coordinates, the velocity c
1428  and vertical direction respectively, are given by (see Fig.2) :  and vertical direction respectively, are given by (see Fig.2) :
1429    
1430  \begin{equation*}  \begin{equation*}
1431  u=r\cos \phi \frac{D\lambda }{Dt}  u=r\cos \varphi \frac{D\lambda }{Dt}
1432  \end{equation*}  \end{equation*}
1433    
1434  \begin{equation*}  \begin{equation*}
1435  v=r\frac{D\phi }{Dt}\qquad  v=r\frac{D\varphi }{Dt}\qquad
1436  \end{equation*}  \end{equation*}
1437  $\qquad \qquad \qquad \qquad $  $\qquad \qquad \qquad \qquad $
1438    
1439  \begin{equation*}  \begin{equation*}
1440  \dot{r}=\frac{Dr}{Dt}  \dot{r}=\frac{Dr}{Dt}
1441  \end{equation*}  \end{equation*}
1442    
1443  Here $\phi $ is the latitude, $\lambda $ the longitude, $r$ the radial  Here $\varphi $ is the latitude, $\lambda $ the longitude, $r$ the radial
1444  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
1445  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.
1446    
# Line 1392  The `grad' ($\nabla $) and `div' ($\nabl Line 1448  The `grad' ($\nabla $) and `div' ($\nabl
1448  spherical coordinates:  spherical coordinates:
1449    
1450  \begin{equation*}  \begin{equation*}
1451  \nabla \equiv \left( \frac{1}{r\cos \phi }\frac{\partial }{\partial \lambda }%  \nabla \equiv \left( \frac{1}{r\cos \varphi }\frac{\partial }{\partial \lambda }
1452  ,\frac{1}{r}\frac{\partial }{\partial \phi },\frac{\partial }{\partial r}%  ,\frac{1}{r}\frac{\partial }{\partial \varphi },\frac{\partial }{\partial r}
1453  \right)  \right)
1454  \end{equation*}  \end{equation*}
1455    
1456  \begin{equation*}  \begin{equation*}
1457  \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
1458  \lambda }+\frac{\partial }{\partial \phi }\left( v\cos \phi \right) \right\}  \lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\}
1459  +\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}
1460  \end{equation*}  \end{equation*}
1461    
1462  %%%% \end{document}  %tci%\end{document}

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