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revision 1.6 by cnh, Wed Oct 24 15:21:27 2001 UTC revision 1.15 by cnh, Wed Nov 21 16:33:17 2001 UTC
# Line 54  MITgcm has a number of novel aspects: Line 54  MITgcm has a number of novel aspects:
54  \begin{itemize}  \begin{itemize}
55  \item it can be used to study both atmospheric and oceanic phenomena; one  \item it can be used to study both atmospheric and oceanic phenomena; one
56  hydrodynamical kernel is used to drive forward both atmospheric and oceanic  hydrodynamical kernel is used to drive forward both atmospheric and oceanic
57  models - see fig  models - see fig \ref{fig:onemodel}
 \marginpar{  
 Fig.1 One model}\ref{fig:onemodel}  
58    
59  %% CNHbegin  %% CNHbegin
60  \input{part1/one_model_figure}  \input{part1/one_model_figure}
61  %% CNHend  %% CNHend
62    
63  \item it has a non-hydrostatic capability and so can be used to study both  \item it has a non-hydrostatic capability and so can be used to study both
64  small-scale and large scale processes - see fig  small-scale and large scale processes - see fig \ref{fig:all-scales}
 \marginpar{  
 Fig.2 All scales}\ref{fig:all-scales}  
65    
66  %% CNHbegin  %% CNHbegin
67  \input{part1/all_scales_figure}  \input{part1/all_scales_figure}
# Line 73  Fig.2 All scales}\ref{fig:all-scales} Line 69  Fig.2 All scales}\ref{fig:all-scales}
69    
70  \item finite volume techniques are employed yielding an intuitive  \item finite volume techniques are employed yielding an intuitive
71  discretization and support for the treatment of irregular geometries using  discretization and support for the treatment of irregular geometries using
72  orthogonal curvilinear grids and shaved cells - see fig  orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes}
 \marginpar{  
 Fig.3 Finite volumes}\ref{fig:finite-volumes}  
73    
74  %% CNHbegin  %% CNHbegin
75  \input{part1/fvol_figure}  \input{part1/fvol_figure}
# Line 89  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 Eighth ECMWF Workshop on the Use of Parallel Processors
123    in Meteorology, pages 406-425
124    World Scientific Publishing Co: UK
125    
126    Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999)
127    Construction of the adjoint MIT ocean general circulation model and
128    application to Atlantic heat transport variability
129    J. Geophysical Res., 104(C12), 29,529-29,547.
130    
131    
132    \end{verbatim}
133    
134  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
135  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.
# Line 102  give a feel for the wide range of proble Line 141  give a feel for the wide range of proble
141    
142  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,
143  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
144  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
145  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
146  of them here. A more detailed description of the underlying formulation,  of them here. A more detailed description of the underlying formulation,
147  numerical algorithm and implementation that lie behind these calculations is  numerical algorithm and implementation that lie behind these calculations is
148  given later. Indeed many of the illustrative examples shown below can be  given later. Indeed many of the illustrative examples shown below can be
149  easily reproduced: simply download the model (the minimum you need is a PC  easily reproduced: simply download the model (the minimum you need is a PC
150  running linux, together with a FORTRAN\ 77 compiler) and follow the examples  running Linux, together with a FORTRAN\ 77 compiler) and follow the examples
151  described in detail in the documentation.  described in detail in the documentation.
152    
153  \subsection{Global atmosphere: `Held-Suarez' benchmark}  \subsection{Global atmosphere: `Held-Suarez' benchmark}
154    
155  A novel feature of MITgcm is its ability to simulate both atmospheric and  A novel feature of MITgcm is its ability to simulate, using one basic algorithm,
156  oceanographic flows at both small and large scales.  both atmospheric and oceanographic flows at both small and large scales.
157    
158  Fig.E1a.\ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$  Figure \ref{fig:eddy_cs} shows an instantaneous plot of the 500$mb$
159  temperature field obtained using the atmospheric isomorph of MITgcm run at  temperature field obtained using the atmospheric isomorph of MITgcm run at
160  2.8$^{\circ }$ resolution on the cubed sphere. We see cold air over the pole  2.8$^{\circ }$ resolution on the cubed sphere. We see cold air over the pole
161  (blue) and warm air along an equatorial band (red). Fully developed  (blue) and warm air along an equatorial band (red). Fully developed
# Line 132  there are no mountains or land-sea contr Line 171  there are no mountains or land-sea contr
171  %% CNHend  %% CNHend
172    
173  As described in Adcroft (2001), a `cubed sphere' is used to discretize the  As described in Adcroft (2001), a `cubed sphere' is used to discretize the
174  globe permitting a uniform gridding and obviated the need to fourier filter.  globe permitting a uniform griding and obviated the need to Fourier filter.
175  The `vector-invariant' form of MITgcm supports any orthogonal curvilinear  The `vector-invariant' form of MITgcm supports any orthogonal curvilinear
176  grid, of which the cubed sphere is just one of many choices.  grid, of which the cubed sphere is just one of many choices.
177    
178  Fig.E1b shows the 5-year mean, zonally averaged potential temperature, zonal  Figure \ref{fig:hs_zave_u} shows the 5-year mean, zonally averaged zonal
179  wind and meridional overturning streamfunction from a 20-level version of  wind from a 20-level configuration of
180  the model. It compares favorable with more conventional spatial  the model. It compares favorable with more conventional spatial
181  discretization approaches.  discretization approaches. The two plots show the field calculated using the
182    cube-sphere grid and the flow calculated using a regular, spherical polar
183  A regular spherical lat-lon grid can also be used.  latitude-longitude grid. Both grids are supported within the model.
184    
185  %% CNHbegin  %% CNHbegin
186  \input{part1/hs_zave_u_figure}  \input{part1/hs_zave_u_figure}
# Line 157  diffusive patterns of ocean currents. Bu Line 196  diffusive patterns of ocean currents. Bu
196  increased until the baroclinic instability process is resolved, numerical  increased until the baroclinic instability process is resolved, numerical
197  solutions of a different and much more realistic kind, can be obtained.  solutions of a different and much more realistic kind, can be obtained.
198    
199  Fig. ?.? shows the surface temperature and velocity field obtained from  Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity
200  MITgcm run at $\frac{1}{6}^{\circ }$ horizontal resolution on a $lat-lon$  field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal
201    resolution on a $lat-lon$
202  grid in which the pole has been rotated by 90$^{\circ }$ on to the equator  grid in which the pole has been rotated by 90$^{\circ }$ on to the equator
203  (to avoid the converging of meridian in northern latitudes). 21 vertical  (to avoid the converging of meridian in northern latitudes). 21 vertical
204  levels are used in the vertical with a `lopped cell' representation of  levels are used in the vertical with a `lopped cell' representation of
205  topography. The development and propagation of anomalously warm and cold  topography. The development and propagation of anomalously warm and cold
206  eddies can be clearly been seen in the Gulf Stream region. The transport of  eddies can be clearly seen in the Gulf Stream region. The transport of
207  warm water northward by the mean flow of the Gulf Stream is also clearly  warm water northward by the mean flow of the Gulf Stream is also clearly
208  visible.  visible.
209    
210  %% CNHbegin  %% CNHbegin
211  \input{part1/ocean_gyres_figure}  \input{part1/atl6_figure}
212  %% CNHend  %% CNHend
213    
214    
215  \subsection{Global ocean circulation}  \subsection{Global ocean circulation}
216    
217  Fig.E2a shows the pattern of ocean currents at the surface of a 4$^{\circ }$  Figure \ref{fig:large-scale-circ} (top) shows the pattern of ocean currents at
218    the surface of a 4$^{\circ }$
219  global ocean model run with 15 vertical levels. Lopped cells are used to  global ocean model run with 15 vertical levels. Lopped cells are used to
220  represent topography on a regular $lat-lon$ grid extending from 70$^{\circ  represent topography on a regular $lat-lon$ grid extending from 70$^{\circ
221  }N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with  }N $ to 70$^{\circ }S$. The model is driven using monthly-mean winds with
# Line 182  mixed boundary conditions on temperature Line 223  mixed boundary conditions on temperature
223  transfer properties of ocean eddies, convection and mixing is parameterized  transfer properties of ocean eddies, convection and mixing is parameterized
224  in this model.  in this model.
225    
226  Fig.E2b shows the meridional overturning circulation of the global ocean in  Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning
227  Sverdrups.  circulation of the global ocean in Sverdrups.
228    
229  %%CNHbegin  %%CNHbegin
230  \input{part1/global_circ_figure}  \input{part1/global_circ_figure}
# Line 195  Dense plumes generated by localized cool Line 236  Dense plumes generated by localized cool
236  ocean may be influenced by rotation when the deformation radius is smaller  ocean may be influenced by rotation when the deformation radius is smaller
237  than the width of the cooling region. Rather than gravity plumes, the  than the width of the cooling region. Rather than gravity plumes, the
238  mechanism for moving dense fluid down the shelf is then through geostrophic  mechanism for moving dense fluid down the shelf is then through geostrophic
239  eddies. The simulation shown in the figure (blue is cold dense fluid, red is  eddies. The simulation shown in the figure \ref{fig:convect-and-topo}
240    (blue is cold dense fluid, red is
241  warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to  warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to
242  trigger convection by surface cooling. The cold, dense water falls down the  trigger convection by surface cooling. The cold, dense water falls down the
243  slope but is deflected along the slope by rotation. It is found that  slope but is deflected along the slope by rotation. It is found that
# Line 214  presence of complex geometry makes it an Line 256  presence of complex geometry makes it an
256  dynamics and mixing in oceanic canyons and ridges driven by large amplitude  dynamics and mixing in oceanic canyons and ridges driven by large amplitude
257  barotropic tidal currents imposed through open boundary conditions.  barotropic tidal currents imposed through open boundary conditions.
258    
259  Fig. ?.? shows the influence of cross-slope topographic variations on  Fig. \ref{fig:boundary-forced-wave} shows the influence of cross-slope
260    topographic variations on
261  internal wave breaking - the cross-slope velocity is in color, the density  internal wave breaking - the cross-slope velocity is in color, the density
262  contoured. The internal waves are excited by application of open boundary  contoured. The internal waves are excited by application of open boundary
263  conditions on the left.\ They propagate to the sloping boundary (represented  conditions on the left. They propagate to the sloping boundary (represented
264  using MITgcm's finite volume spatial discretization) where they break under  using MITgcm's finite volume spatial discretization) where they break under
265  nonhydrostatic dynamics.  nonhydrostatic dynamics.
266    
# Line 231  Forward and tangent linear counterparts Line 274  Forward and tangent linear counterparts
274  `automatic adjoint compiler'. These can be used in parameter sensitivity and  `automatic adjoint compiler'. These can be used in parameter sensitivity and
275  data assimilation studies.  data assimilation studies.
276    
277  As one example of application of the MITgcm adjoint, Fig.E4 maps the  As one example of application of the MITgcm adjoint, Figure \ref{fig:hf-sensitivity}
278  gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude  maps the gradient $\frac{\partial J}{\partial \mathcal{H}}$where $J$ is the magnitude
279  of the overturning streamfunction shown in fig?.? at 40$^{\circ }$N and $  of the overturning stream-function shown in figure \ref{fig:large-scale-circ}
280  \mathcal{H}$ is the air-sea heat flux 100 years before. We see that $J$ is  at 60$^{\circ }$N and $
281    \mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over
282    a 100 year period. We see that $J$ is
283  sensitive to heat fluxes over the Labrador Sea, one of the important sources  sensitive to heat fluxes over the Labrador Sea, one of the important sources
284  of deep water for the thermohaline circulations. This calculation also  of deep water for the thermohaline circulations. This calculation also
285  yields sensitivities to all other model parameters.  yields sensitivities to all other model parameters.
# Line 248  yields sensitivities to all other model Line 293  yields sensitivities to all other model
293  An important application of MITgcm is in state estimation of the global  An important application of MITgcm is in state estimation of the global
294  ocean circulation. An appropriately defined `cost function', which measures  ocean circulation. An appropriately defined `cost function', which measures
295  the departure of the model from observations (both remotely sensed and  the departure of the model from observations (both remotely sensed and
296  insitu) over an interval of time, is minimized by adjusting `control  in-situ) over an interval of time, is minimized by adjusting `control
297  parameters' such as air-sea fluxes, the wind field, the initial conditions  parameters' such as air-sea fluxes, the wind field, the initial conditions
298  etc. Figure ?.? shows an estimate of the time-mean surface elevation of the  etc. Figure \ref{fig:assimilated-globes} shows the large scale planetary
299  ocean obtained by bringing the model in to consistency with altimetric and  circulation and a Hopf-Muller plot of Equatorial sea-surface height.
300  in-situ observations over the period 1992-1997.  Both are obtained from assimilation bringing the model in to
301    consistency with altimetric and in-situ observations over the period
302    1992-1997.
303    
304  %% CNHbegin  %% CNHbegin
305  \input{part1/globes_figure}  \input{part1/assim_figure}
306  %% CNHend  %% CNHend
307    
308  \subsection{Ocean biogeochemical cycles}  \subsection{Ocean biogeochemical cycles}
# Line 263  in-situ observations over the period 199 Line 310  in-situ observations over the period 199
310  MITgcm is being used to study global biogeochemical cycles in the ocean. For  MITgcm is being used to study global biogeochemical cycles in the ocean. For
311  example one can study the effects of interannual changes in meteorological  example one can study the effects of interannual changes in meteorological
312  forcing and upper ocean circulation on the fluxes of carbon dioxide and  forcing and upper ocean circulation on the fluxes of carbon dioxide and
313  oxygen between the ocean and atmosphere. The figure shows the annual air-sea  oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows
314  flux of oxygen and its relation to density outcrops in the southern oceans  the annual air-sea flux of oxygen and its relation to density outcrops in
315  from a single year of a global, interannually varying simulation.  the southern oceans from a single year of a global, interannually varying
316    simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution
317    telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown).
318    
319  %%CNHbegin  %%CNHbegin
320  \input{part1/biogeo_figure}  \input{part1/biogeo_figure}
# Line 273  from a single year of a global, interann Line 322  from a single year of a global, interann
322    
323  \subsection{Simulations of laboratory experiments}  \subsection{Simulations of laboratory experiments}
324    
325  Figure ?.? shows MITgcm being used to simulate a laboratory experiment  Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a
326  enquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An  laboratory experiment inquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An
327  initially homogeneous tank of water ($1m$ in diameter) is driven from its  initially homogeneous tank of water ($1m$ in diameter) is driven from its
328  free surface by a rotating heated disk. The combined action of mechanical  free surface by a rotating heated disk. The combined action of mechanical
329  and thermal forcing creates a lens of fluid which becomes baroclinically  and thermal forcing creates a lens of fluid which becomes baroclinically
330  unstable. The stratification and depth of penetration of the lens is  unstable. The stratification and depth of penetration of the lens is
331  arrested by its instability in a process analogous to that whic sets the  arrested by its instability in a process analogous to that which sets the
332  stratification of the ACC.  stratification of the ACC.
333    
334  %%CNHbegin  %%CNHbegin
# Line 293  stratification of the ACC. Line 342  stratification of the ACC.
342    
343  To render atmosphere and ocean models from one dynamical core we exploit  To render atmosphere and ocean models from one dynamical core we exploit
344  `isomorphisms' between equation sets that govern the evolution of the  `isomorphisms' between equation sets that govern the evolution of the
345  respective fluids - see fig.4  respective fluids - see figure \ref{fig:isomorphic-equations}.
346  \marginpar{  One system of hydrodynamical equations is written down
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down  
347  and encoded. The model variables have different interpretations depending on  and encoded. The model variables have different interpretations depending on
348  whether the atmosphere or ocean is being studied. Thus, for example, the  whether the atmosphere or ocean is being studied. Thus, for example, the
349  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are  vertical coordinate `$r$' is interpreted as pressure, $p$, if we are
350  modeling the atmosphere and height, $z$, if we are modeling the ocean.  modeling the atmosphere (left hand side of figure \ref{fig:isomorphic-equations})
351    and height, $z$, if we are modeling the ocean (right hand side of figure
352    \ref{fig:isomorphic-equations}).
353    
354  %%CNHbegin  %%CNHbegin
355  \input{part1/zandpcoord_figure.tex}  \input{part1/zandpcoord_figure.tex}
# Line 311  velocity $\vec{\mathbf{v}}$, active trac Line 361  velocity $\vec{\mathbf{v}}$, active trac
361  depend on $\theta $, $S$, and $p$. The equations that govern the evolution  depend on $\theta $, $S$, and $p$. The equations that govern the evolution
362  of these fields, obtained by applying the laws of classical mechanics and  of these fields, obtained by applying the laws of classical mechanics and
363  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of  thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of
364  a generic vertical coordinate, $r$, see fig.5  a generic vertical coordinate, $r$, so that the appropriate
365  \marginpar{  kinematic boundary conditions can be applied isomorphically
366  Fig.5 The vertical coordinate of model}:  see figure \ref{fig:zandp-vert-coord}.
367    
368  %%CNHbegin  %%CNHbegin
369  \input{part1/vertcoord_figure.tex}  \input{part1/vertcoord_figure.tex}
# Line 322  Fig.5 The vertical coordinate of model}: Line 372  Fig.5 The vertical coordinate of model}:
372  \begin{equation*}  \begin{equation*}
373  \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}  \frac{D\vec{\mathbf{v}_{h}}}{Dt}+\left( 2\vec{\Omega}\times \vec{\mathbf{v}}
374  \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}  \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}
375  \text{ horizontal mtm}  \text{ horizontal mtm} \label{eq:horizontal_mtm}
376  \end{equation*}  \end{equation*}
377    
378  \begin{equation*}  \begin{equation}
379  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{  \frac{D\dot{r}}{Dt}+\widehat{k}\cdot \left( 2\vec{\Omega}\times \vec{\mathbf{
380  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{  v}}\right) +\frac{\partial \phi }{\partial r}+b=\mathcal{F}_{\dot{r}}\text{
381  vertical mtm}  vertical mtm} \label{eq:vertical_mtm}
382  \end{equation*}  \end{equation}
383    
384  \begin{equation}  \begin{equation}
385  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{  \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{
386  \partial r}=0\text{ continuity}  \label{eq:continuous}  \partial r}=0\text{ continuity}  \label{eq:continuity}
387  \end{equation}  \end{equation}
388    
389  \begin{equation*}  \begin{equation}
390  b=b(\theta ,S,r)\text{ equation of state}  b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state}
391  \end{equation*}  \end{equation}
392    
393  \begin{equation*}  \begin{equation}
394  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}  \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature}
395  \end{equation*}  \label{eq:potential_temperature}
396    \end{equation}
397    
398  \begin{equation*}  \begin{equation}
399  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}  \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity}
400  \end{equation*}  \label{eq:humidity_salt}
401    \end{equation}
402    
403  Here:  Here:
404    
# Line 410  S\text{ is specific humidity in the atmo Line 462  S\text{ is specific humidity in the atmo
462  \end{equation*}  \end{equation*}
463    
464  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
465  extensive `physics' packages for atmosphere and ocean described in Chapter 6.  `physics' and forcing packages for atmosphere and ocean. These are described
466    in later chapters.
467    
468  \subsection{Kinematic Boundary conditions}  \subsection{Kinematic Boundary conditions}
469    
470  \subsubsection{vertical}  \subsubsection{vertical}
471    
472  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}):
473    
474  \begin{equation}  \begin{equation}
475  \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 425  at fixed and moving $r$ surfaces we set Line 478  at fixed and moving $r$ surfaces we set
478    
479  \begin{equation}  \begin{equation}
480  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \  \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \
481  (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc}  (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc}
482  \end{equation}  \end{equation}
483    
484  Here  Here
# Line 447  where $\vec{\mathbf{n}}$ is the normal t Line 500  where $\vec{\mathbf{n}}$ is the normal t
500    
501  \subsection{Atmosphere}  \subsection{Atmosphere}
502    
503  In the atmosphere, see fig.5, we interpret:  In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret:
504    
505  \begin{equation}  \begin{equation}
506  r=p\text{ is the pressure}  \label{eq:atmos-r}  r=p\text{ is the pressure}  \label{eq:atmos-r}
# Line 518  The boundary conditions at top and botto Line 571  The boundary conditions at top and botto
571  atmosphere)}  \label{eq:moving-bc-atmos}  atmosphere)}  \label{eq:moving-bc-atmos}
572  \end{eqnarray}  \end{eqnarray}
573    
574  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})
575  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 $p$
576  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).  coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}).
577    
578  \subsection{Ocean}  \subsection{Ocean}
# Line 555  w &=&\frac{D\eta }{Dt}\text{ at }r=R_{mo Line 608  w &=&\frac{D\eta }{Dt}\text{ at }r=R_{mo
608  \end{eqnarray}  \end{eqnarray}
609  where $\eta $ is the elevation of the free surface.  where $\eta $ is the elevation of the free surface.
610    
611  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
612    of oceanic equations
613  which, for convenience, are written out in $z$ coordinates in Appendix Ocean  which, for convenience, are written out in $z$ coordinates in Appendix Ocean
614  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).  - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}).
615    
# Line 568  Let us separate $\phi $ in to surface, h Line 622  Let us separate $\phi $ in to surface, h
622  \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)
623  \label{eq:phi-split}  \label{eq:phi-split}
624  \end{equation}  \end{equation}
625  and write eq(\ref{incompressible}a,b) in the form:  and write eq(\ref{eq:incompressible}) in the form:
626    
627  \begin{equation}  \begin{equation}
628  \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 661  In the above `${r}$' is the distance fro Line 715  In the above `${r}$' is the distance fro
715    
716  Grad and div operators in spherical coordinates are defined in appendix  Grad and div operators in spherical coordinates are defined in appendix
717  OPERATORS.  OPERATORS.
 \marginpar{  
 Fig.6 Spherical polar coordinate system.}  
718    
719  %%CNHbegin  %%CNHbegin
720  \input{part1/sphere_coord_figure.tex}  \input{part1/sphere_coord_figure.tex}
# Line 681  r $ in, for example, (\ref{eq:gu-speheri Line 733  r $ in, for example, (\ref{eq:gu-speheri
733  the radius of the earth.  the radius of the earth.
734    
735  \subsubsection{Hydrostatic and quasi-hydrostatic forms}  \subsubsection{Hydrostatic and quasi-hydrostatic forms}
736    \label{sec:hydrostatic_and_quasi-hydrostatic_forms}
737    
738  These are discussed at length in Marshall et al (1997a).  These are discussed at length in Marshall et al (1997a).
739    
# Line 724  In the non-hydrostatic ocean model all t Line 777  In the non-hydrostatic ocean model all t
777  three dimensional elliptic equation must be solved subject to Neumann  three dimensional elliptic equation must be solved subject to Neumann
778  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
779  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
780  incompressible condition eq(\ref{eq:continuous})c has already filtered out  incompressible condition eq(\ref{eq:continuity}) has already filtered out
781  acoustic modes. It does, however, ensure that the gravity waves are treated  acoustic modes. It does, however, ensure that the gravity waves are treated
782  accurately with an exact dispersion relation. The \textbf{NH} set has a  accurately with an exact dispersion relation. The \textbf{NH} set has a
783  complete angular momentum principle and consistent energetics - see White  complete angular momentum principle and consistent energetics - see White
# Line 773  coordinates are supported - see eqs(\ref Line 826  coordinates are supported - see eqs(\ref
826  \subsection{Solution strategy}  \subsection{Solution strategy}
827    
828  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{
829  NH} models is summarized in Fig.7.  NH} models is summarized in Figure \ref{fig:solution-strategy}.
830  \marginpar{  Under all dynamics, a 2-d elliptic equation is
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is  
831  first solved to find the surface pressure and the hydrostatic pressure at  first solved to find the surface pressure and the hydrostatic pressure at
832  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
833  \textbf{QH} dynamics, the horizontal momentum equations are then stepped  \textbf{QH} dynamics, the horizontal momentum equations are then stepped
# Line 799  Marshall et al, 1997) resulting in a non Line 851  Marshall et al, 1997) resulting in a non
851  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.  hydrostatic limit, is as computationally economic as the \textbf{HPEs}.
852    
853  \subsection{Finding the pressure field}  \subsection{Finding the pressure field}
854    \label{sec:finding_the_pressure_field}
855    
856  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the  Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the
857  pressure field must be obtained diagnostically. We proceed, as before, by  pressure field must be obtained diagnostically. We proceed, as before, by
# Line 831  atmospheric pressure pushing down on the Line 884  atmospheric pressure pushing down on the
884    
885  \subsubsection{Surface pressure}  \subsubsection{Surface pressure}
886    
887  The surface pressure equation can be obtained by integrating continuity, (  The surface pressure equation can be obtained by integrating continuity,
888  \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$  (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$
889    
890  \begin{equation*}  \begin{equation*}
891  \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}
# Line 857  r $. The above can be rearranged to yiel Line 910  r $. The above can be rearranged to yiel
910  where we have incorporated a source term.  where we have incorporated a source term.
911    
912  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential  Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential
913  (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can  (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can
914  be written  be written
915  \begin{equation}  \begin{equation}
916  \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)
# Line 865  be written Line 918  be written
918  \end{equation}  \end{equation}
919  where $b_{s}$ is the buoyancy at the surface.  where $b_{s}$ is the buoyancy at the surface.
920    
921  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
922  {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
923  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free  elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free
924  surface' and `rigid lid' approaches are available.  surface' and `rigid lid' approaches are available.
925    
926  \subsubsection{Non-hydrostatic pressure}  \subsubsection{Non-hydrostatic pressure}
927    
928  Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{  Taking the horizontal divergence of (\ref{eq:mom-h}) and adding
929  \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation  $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation
930  (\ref{incompressible}), we deduce that:  (\ref{eq:continuity}), we deduce that:
931    
932  \begin{equation}  \begin{equation}
933  \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{
# Line 904  tangential component of velocity, $v_{T} Line 957  tangential component of velocity, $v_{T}
957  depending on the form chosen for the dissipative terms in the momentum  depending on the form chosen for the dissipative terms in the momentum
958  equations - see below.  equations - see below.
959    
960  Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that:  Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that:
961    
962  \begin{equation}  \begin{equation}
963  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}  \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}}
# Line 944  If the flow is `close' to hydrostatic ba Line 997  If the flow is `close' to hydrostatic ba
997  converges rapidly because $\phi _{nh}\ $is then only a small correction to  converges rapidly because $\phi _{nh}\ $is then only a small correction to
998  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).
999    
1000  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})
1001  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.
1002    
1003  \subsection{Forcing/dissipation}  \subsection{Forcing/dissipation}
# Line 952  does not vanish at $r=R_{moving}$, and s Line 1005  does not vanish at $r=R_{moving}$, and s
1005  \subsubsection{Forcing}  \subsubsection{Forcing}
1006    
1007  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
1008  `physics packages' described in detail in chapter ??.  `physics packages' and forcing packages. These are described later on.
1009    
1010  \subsubsection{Dissipation}  \subsubsection{Dissipation}
1011    
# Line 1000  salinity ... ). Line 1053  salinity ... ).
1053  \subsection{Vector invariant form}  \subsection{Vector invariant form}
1054    
1055  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
1056  {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:
1057    
1058  \begin{equation}  \begin{equation}
1059  \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}
# Line 1018  to discretize the model. Line 1071  to discretize the model.
1071    
1072  \subsection{Adjoint}  \subsection{Adjoint}
1073    
1074  Tangent linear and adjoint counterparts of the forward model and described  Tangent linear and adjoint counterparts of the forward model are described
1075  in Chapter 5.  in Chapter 5.
1076    
1077  % $Header$  % $Header$
# Line 1140  _{o}(p_{o})=g~Z_{topo}$, defined: Line 1193  _{o}(p_{o})=g~Z_{topo}$, defined:
1193  The final form of the HPE's in p coordinates is then:  The final form of the HPE's in p coordinates is then:
1194  \begin{eqnarray}  \begin{eqnarray}
1195  \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}}
1196  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\  _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \label{eq:atmos-prime} \\
1197  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\  \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\
1198  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{  \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{
1199  \partial p} &=&0 \\  \partial p} &=&0 \\
1200  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\  \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\
1201  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime}  \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }
1202  \end{eqnarray}  \end{eqnarray}
1203    
1204  % $Header$  % $Header$
# Line 1164  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z} Line 1217  _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}
1217  \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}
1218  &=&\epsilon _{nh}\mathcal{F}_{w} \\  &=&\epsilon _{nh}\mathcal{F}_{w} \\
1219  \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}}
1220  _{h}+\frac{\partial w}{\partial z} &=&0 \\  _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\
1221  \rho &=&\rho (\theta ,S,p) \\  \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\
1222  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\  \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\
1223  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq}  \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt}
1224    \label{eq:non-boussinesq}
1225  \end{eqnarray}  \end{eqnarray}
1226  These equations permit acoustics modes, inertia-gravity waves,  These equations permit acoustics modes, inertia-gravity waves,
1227  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline  non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline
1228  mode. As written, they cannot be integrated forward consistently - if we  mode. As written, they cannot be integrated forward consistently - if we
1229  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
1230  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref  consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref
# Line 1186  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp Line 1240  _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexp
1240  \end{equation}  \end{equation}
1241    
1242  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
1243  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:  
1244  \begin{equation}  \begin{equation}
1245  \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{
1246  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}  v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure}

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