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 %%%% \part{MIT GCM basics} | 
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 % Section: Overview | 
 % Section: Overview | 
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 % $Header$ | 
 % $Header$ | 
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 % $Name$ | 
 % $Name$ | 
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| 40 | 
 \section{Introduction} | 
 This document provides the reader with the information necessary to | 
 | 
  | 
  | 
 | 
 This documentation provides the reader with the information necessary to | 
  | 
| 41 | 
 carry out numerical experiments using MITgcm. It gives a comprehensive | 
 carry out numerical experiments using MITgcm. It gives a comprehensive | 
| 42 | 
 description of the continuous equations on which the model is based, the | 
 description of the continuous equations on which the model is based, the | 
| 43 | 
 numerical algorithms the model employs and a description of the associated | 
 numerical algorithms the model employs and a description of the associated | 
| 47 | 
 both process and general circulation studies of the atmosphere and ocean are | 
 both process and general circulation studies of the atmosphere and ocean are | 
| 48 | 
 also presented. | 
 also presented. | 
| 49 | 
  | 
  | 
| 50 | 
  | 
 \section{Introduction} | 
| 51 | 
  | 
 \begin{rawhtml} | 
| 52 | 
  | 
 <!-- CMIREDIR:innovations: --> | 
| 53 | 
  | 
 \end{rawhtml} | 
| 54 | 
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| 55 | 
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| 56 | 
 MITgcm has a number of novel aspects: | 
 MITgcm has a number of novel aspects: | 
| 57 | 
  | 
  | 
| 58 | 
 \begin{itemize} | 
 \begin{itemize} | 
| 59 | 
 \item it can be used to study both atmospheric and oceanic phenomena; one | 
 \item it can be used to study both atmospheric and oceanic phenomena; one | 
| 60 | 
 hydrodynamical kernel is used to drive forward both atmospheric and oceanic | 
 hydrodynamical kernel is used to drive forward both atmospheric and oceanic | 
| 61 | 
 models - see fig% | 
 models - see fig \ref{fig:onemodel} | 
 | 
 \marginpar{ | 
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 | 
 Fig.1 One model}\ref{fig:onemodel} | 
  | 
| 62 | 
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| 63 | 
 %% CNHbegin | 
 %% CNHbegin | 
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 \input{part1/one_model_figure} | 
 \input{part1/one_model_figure} | 
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 %% CNHend | 
 %% CNHend | 
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  | 
  | 
| 67 | 
 \item it has a non-hydrostatic capability and so can be used to study both | 
 \item it has a non-hydrostatic capability and so can be used to study both | 
| 68 | 
 small-scale and large scale processes - see fig % | 
 small-scale and large scale processes - see fig \ref{fig:all-scales} | 
 | 
 \marginpar{ | 
  | 
 | 
 Fig.2 All scales}\ref{fig:all-scales} | 
  | 
| 69 | 
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| 70 | 
 %% CNHbegin | 
 %% CNHbegin | 
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 \input{part1/all_scales_figure} | 
 \input{part1/all_scales_figure} | 
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  | 
  | 
| 74 | 
 \item finite volume techniques are employed yielding an intuitive | 
 \item finite volume techniques are employed yielding an intuitive | 
| 75 | 
 discretization and support for the treatment of irregular geometries using | 
 discretization and support for the treatment of irregular geometries using | 
| 76 | 
 orthogonal curvilinear grids and shaved cells - see fig % | 
 orthogonal curvilinear grids and shaved cells - see fig \ref{fig:finite-volumes} | 
 | 
 \marginpar{ | 
  | 
 | 
 Fig.3 Finite volumes}\ref{fig:finite-volumes} | 
  | 
| 77 | 
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| 78 | 
 %% CNHbegin | 
 %% CNHbegin | 
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 \input{part1/fvol_figure} | 
 \input{part1/fvol_figure} | 
| 88 | 
 \end{itemize} | 
 \end{itemize} | 
| 89 | 
  | 
  | 
| 90 | 
 Key publications reporting on and charting the development of the model are | 
 Key publications reporting on and charting the development of the model are | 
| 91 | 
 listed in an Appendix. | 
 \cite{hill:95,marshall:97a,marshall:97b,adcroft:97,marshall:98,adcroft:99,hill:99,maro-eta:99,adcroft:04a,adcroft:04b,marshall:04}: | 
| 92 | 
  | 
  | 
| 93 | 
  | 
 \begin{verbatim} | 
| 94 | 
  | 
 Hill, C. and J. Marshall, (1995) | 
| 95 | 
  | 
 Application of a Parallel Navier-Stokes Model to Ocean Circulation in  | 
| 96 | 
  | 
 Parallel Computational Fluid Dynamics | 
| 97 | 
  | 
 In Proceedings of Parallel Computational Fluid Dynamics: Implementations  | 
| 98 | 
  | 
 and Results Using Parallel Computers, 545-552. | 
| 99 | 
  | 
 Elsevier Science B.V.: New York | 
| 100 | 
  | 
  | 
| 101 | 
  | 
 Marshall, J., C. Hill, L. Perelman, and A. Adcroft, (1997) | 
| 102 | 
  | 
 Hydrostatic, quasi-hydrostatic, and nonhydrostatic ocean modeling | 
| 103 | 
  | 
 J. Geophysical Res., 102(C3), 5733-5752. | 
| 104 | 
  | 
  | 
| 105 | 
  | 
 Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, (1997) | 
| 106 | 
  | 
 A finite-volume, incompressible Navier Stokes model for studies of the ocean | 
| 107 | 
  | 
 on parallel computers, | 
| 108 | 
  | 
 J. Geophysical Res., 102(C3), 5753-5766. | 
| 109 | 
  | 
  | 
| 110 | 
  | 
 Adcroft, A.J., Hill, C.N. and J. Marshall, (1997) | 
| 111 | 
  | 
 Representation of topography by shaved cells in a height coordinate ocean | 
| 112 | 
  | 
 model | 
| 113 | 
  | 
 Mon Wea Rev, vol 125, 2293-2315 | 
| 114 | 
  | 
  | 
| 115 | 
  | 
 Marshall, J., Jones, H. and C. Hill, (1998) | 
| 116 | 
  | 
 Efficient ocean modeling using non-hydrostatic algorithms | 
| 117 | 
  | 
 Journal of Marine Systems, 18, 115-134 | 
| 118 | 
  | 
  | 
| 119 | 
  | 
 Adcroft, A., Hill C. and J. Marshall: (1999) | 
| 120 | 
  | 
 A new treatment of the Coriolis terms in C-grid models at both high and low | 
| 121 | 
  | 
 resolutions, | 
| 122 | 
  | 
 Mon. Wea. Rev. Vol 127, pages 1928-1936 | 
| 123 | 
  | 
  | 
| 124 | 
  | 
 Hill, C, Adcroft,A., Jamous,D., and J. Marshall, (1999) | 
| 125 | 
  | 
 A Strategy for Terascale Climate Modeling. | 
| 126 | 
  | 
 In Proceedings of the Eighth ECMWF Workshop on the Use of Parallel Processors | 
| 127 | 
  | 
 in Meteorology, pages 406-425 | 
| 128 | 
  | 
 World Scientific Publishing Co: UK | 
| 129 | 
  | 
  | 
| 130 | 
  | 
 Marotzke, J, Giering,R., Zhang, K.Q., Stammer,D., Hill,C., and T.Lee, (1999) | 
| 131 | 
  | 
 Construction of the adjoint MIT ocean general circulation model and  | 
| 132 | 
  | 
 application to Atlantic heat transport variability | 
| 133 | 
  | 
 J. Geophysical Res., 104(C12), 29,529-29,547. | 
| 134 | 
  | 
  | 
| 135 | 
  | 
 \end{verbatim} | 
| 136 | 
  | 
  | 
| 137 | 
 We begin by briefly showing some of the results of the model in action to | 
 We begin by briefly showing some of the results of the model in action to | 
| 138 | 
 give a feel for the wide range of problems that can be addressed using it. | 
 give a feel for the wide range of problems that can be addressed using it. | 
 | 
 \pagebreak | 
  | 
| 139 | 
  | 
  | 
| 140 | 
 % $Header$ | 
 % $Header$ | 
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 % $Name$ | 
 % $Name$ | 
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  | 
| 143 | 
 \section{Illustrations of the model in action} | 
 \section{Illustrations of the model in action} | 
| 144 | 
  | 
  | 
| 145 | 
 The MITgcm has been designed and used to model a wide range of phenomena, | 
 MITgcm has been designed and used to model a wide range of phenomena, | 
| 146 | 
 from convection on the scale of meters in the ocean to the global pattern of | 
 from convection on the scale of meters in the ocean to the global pattern of | 
| 147 | 
 atmospheric winds - see fig.2\ref{fig:all-scales}. To give a flavor of the | 
 atmospheric winds - see figure \ref{fig:all-scales}. To give a flavor of the | 
| 148 | 
 kinds of problems the model has been used to study, we briefly describe some | 
 kinds of problems the model has been used to study, we briefly describe some | 
| 149 | 
 of them here. A more detailed description of the underlying formulation, | 
 of them here. A more detailed description of the underlying formulation, | 
| 150 | 
 numerical algorithm and implementation that lie behind these calculations is | 
 numerical algorithm and implementation that lie behind these calculations is | 
| 151 | 
 given later. Indeed many of the illustrative examples shown below can be | 
 given later. Indeed many of the illustrative examples shown below can be | 
| 152 | 
 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 | 
| 153 | 
 running linux, together with a FORTRAN\ 77 compiler) and follow the examples | 
 running Linux, together with a FORTRAN\ 77 compiler) and follow the examples | 
| 154 | 
 described in detail in the documentation. | 
 described in detail in the documentation. | 
| 155 | 
  | 
  | 
| 156 | 
 \subsection{Global atmosphere: `Held-Suarez' benchmark} | 
 \subsection{Global atmosphere: `Held-Suarez' benchmark} | 
| 157 | 
  | 
 \begin{rawhtml} | 
| 158 | 
  | 
 <!-- CMIREDIR:atmospheric_example: --> | 
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  | 
 \end{rawhtml} | 
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| 162 | 
  | 
  | 
| 163 | 
 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,  | 
| 164 | 
 oceanographic flows at both small and large scales. | 
 both atmospheric and oceanographic flows at both small and large scales. | 
| 165 | 
  | 
  | 
| 166 | 
 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$mb$ | 
| 167 | 
 temperature field obtained using the atmospheric isomorph of MITgcm run at | 
 temperature field obtained using the atmospheric isomorph of MITgcm run at | 
| 168 | 
 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 | 
| 169 | 
 (blue) and warm air along an equatorial band (red). Fully developed | 
 (blue) and warm air along an equatorial band (red). Fully developed | 
| 179 | 
 %% CNHend | 
 %% CNHend | 
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  | 
  | 
| 181 | 
 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 | 
| 182 | 
 globe permitting a uniform gridding and obviated the need to fourier filter. | 
 globe permitting a uniform griding and obviated the need to Fourier filter. | 
| 183 | 
 The `vector-invariant' form of MITgcm supports any orthogonal curvilinear | 
 The `vector-invariant' form of MITgcm supports any orthogonal curvilinear | 
| 184 | 
 grid, of which the cubed sphere is just one of many choices. | 
 grid, of which the cubed sphere is just one of many choices. | 
| 185 | 
  | 
  | 
| 186 | 
 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 | 
| 187 | 
 wind and meridional overturning streamfunction from a 20-level version of | 
 wind from a 20-level configuration of | 
| 188 | 
 the model. It compares favorable with more conventional spatial | 
 the model. It compares favorable with more conventional spatial | 
| 189 | 
 discretization approaches. | 
 discretization approaches. The two plots show the field calculated using the | 
| 190 | 
  | 
 cube-sphere grid and the flow calculated using a regular, spherical polar | 
| 191 | 
 A regular spherical lat-lon grid can also be used. | 
 latitude-longitude grid. Both grids are supported within the model. | 
| 192 | 
  | 
  | 
| 193 | 
 %% CNHbegin | 
 %% CNHbegin | 
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 \input{part1/hs_zave_u_figure} | 
 \input{part1/hs_zave_u_figure} | 
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 %% CNHend | 
 %% CNHend | 
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  | 
| 197 | 
 \subsection{Ocean gyres} | 
 \subsection{Ocean gyres} | 
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  | 
 \begin{rawhtml} | 
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 <!-- CMIREDIR:oceanic_example: --> | 
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 \end{rawhtml} | 
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 \begin{rawhtml} | 
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 <!-- CMIREDIR:ocean_gyres: --> | 
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 \end{rawhtml} | 
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  | 
  | 
| 205 | 
 Baroclinic instability is a ubiquitous process in the ocean, as well as the | 
 Baroclinic instability is a ubiquitous process in the ocean, as well as the | 
| 206 | 
 atmosphere. Ocean eddies play an important role in modifying the | 
 atmosphere. Ocean eddies play an important role in modifying the | 
| 210 | 
 increased until the baroclinic instability process is resolved, numerical | 
 increased until the baroclinic instability process is resolved, numerical | 
| 211 | 
 solutions of a different and much more realistic kind, can be obtained. | 
 solutions of a different and much more realistic kind, can be obtained. | 
| 212 | 
  | 
  | 
| 213 | 
 Fig. ?.? shows the surface temperature and velocity field obtained from | 
 Figure \ref{fig:ocean-gyres} shows the surface temperature and velocity  | 
| 214 | 
 MITgcm run at $\frac{1}{6}^{\circ }$ horizontal resolution on a $lat-lon$ | 
 field obtained from MITgcm run at $\frac{1}{6}^{\circ }$ horizontal  | 
| 215 | 
  | 
 resolution on a $lat-lon$ | 
| 216 | 
 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 | 
| 217 | 
 (to avoid the converging of meridian in northern latitudes). 21 vertical | 
 (to avoid the converging of meridian in northern latitudes). 21 vertical | 
| 218 | 
 levels are used in the vertical with a `lopped cell' representation of | 
 levels are used in the vertical with a `lopped cell' representation of | 
| 219 | 
 topography. The development and propagation of anomalously warm and cold | 
 topography. The development and propagation of anomalously warm and cold | 
| 220 | 
 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 | 
| 221 | 
 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 | 
| 222 | 
 visible. | 
 visible. | 
| 223 | 
  | 
  | 
| 224 | 
 %% CNHbegin | 
 %% CNHbegin | 
| 225 | 
 \input{part1/ocean_gyres_figure} | 
 \input{part1/atl6_figure} | 
| 226 | 
 %% CNHend | 
 %% CNHend | 
| 227 | 
  | 
  | 
| 228 | 
  | 
  | 
| 229 | 
 \subsection{Global ocean circulation} | 
 \subsection{Global ocean circulation} | 
| 230 | 
  | 
 \begin{rawhtml} | 
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 <!-- CMIREDIR:global_ocean_circulation: --> | 
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  | 
 \end{rawhtml} | 
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  | 
| 234 | 
 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  | 
| 235 | 
  | 
 the surface of a 4$^{\circ }$ | 
| 236 | 
 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 | 
| 237 | 
 represent topography on a regular $lat-lon$ grid extending from 70$^{\circ | 
 represent topography on a regular $lat-lon$ grid extending from 70$^{\circ | 
| 238 | 
 }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 | 
| 240 | 
 transfer properties of ocean eddies, convection and mixing is parameterized | 
 transfer properties of ocean eddies, convection and mixing is parameterized | 
| 241 | 
 in this model. | 
 in this model. | 
| 242 | 
  | 
  | 
| 243 | 
 Fig.E2b shows the meridional overturning circulation of the global ocean in | 
 Figure \ref{fig:large-scale-circ} (bottom) shows the meridional overturning  | 
| 244 | 
 Sverdrups. | 
 circulation of the global ocean in Sverdrups. | 
| 245 | 
  | 
  | 
| 246 | 
 %%CNHbegin | 
 %%CNHbegin | 
| 247 | 
 \input{part1/global_circ_figure} | 
 \input{part1/global_circ_figure} | 
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 %%CNHend | 
 %%CNHend | 
| 249 | 
  | 
  | 
| 250 | 
 \subsection{Convection and mixing over topography} | 
 \subsection{Convection and mixing over topography} | 
| 251 | 
  | 
 \begin{rawhtml} | 
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  | 
 <!-- CMIREDIR:mixing_over_topography: --> | 
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  | 
 \end{rawhtml} | 
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  | 
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  | 
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 Dense plumes generated by localized cooling on the continental shelf of the | 
 Dense plumes generated by localized cooling on the continental shelf of the | 
| 257 | 
 ocean may be influenced by rotation when the deformation radius is smaller | 
 ocean may be influenced by rotation when the deformation radius is smaller | 
| 258 | 
 than the width of the cooling region. Rather than gravity plumes, the | 
 than the width of the cooling region. Rather than gravity plumes, the | 
| 259 | 
 mechanism for moving dense fluid down the shelf is then through geostrophic | 
 mechanism for moving dense fluid down the shelf is then through geostrophic | 
| 260 | 
 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} | 
| 261 | 
  | 
 (blue is cold dense fluid, red is | 
| 262 | 
 warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to | 
 warmer, lighter fluid) employs the non-hydrostatic capability of MITgcm to | 
| 263 | 
 trigger convection by surface cooling. The cold, dense water falls down the | 
 trigger convection by surface cooling. The cold, dense water falls down the | 
| 264 | 
 slope but is deflected along the slope by rotation. It is found that | 
 slope but is deflected along the slope by rotation. It is found that | 
| 271 | 
 %%CNHend | 
 %%CNHend | 
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  | 
  | 
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 \subsection{Boundary forced internal waves} | 
 \subsection{Boundary forced internal waves} | 
| 274 | 
  | 
 \begin{rawhtml} | 
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 <!-- CMIREDIR:boundary_forced_internal_waves: --> | 
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  | 
 \end{rawhtml} | 
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  | 
  | 
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 The unique ability of MITgcm to treat non-hydrostatic dynamics in the | 
 The unique ability of MITgcm to treat non-hydrostatic dynamics in the | 
| 279 | 
 presence of complex geometry makes it an ideal tool to study internal wave | 
 presence of complex geometry makes it an ideal tool to study internal wave | 
| 280 | 
 dynamics and mixing in oceanic canyons and ridges driven by large amplitude | 
 dynamics and mixing in oceanic canyons and ridges driven by large amplitude | 
| 281 | 
 barotropic tidal currents imposed through open boundary conditions. | 
 barotropic tidal currents imposed through open boundary conditions. | 
| 282 | 
  | 
  | 
| 283 | 
 Fig. ?.? shows the influence of cross-slope topographic variations on | 
 Fig. \ref{fig:boundary-forced-wave} shows the influence of cross-slope  | 
| 284 | 
  | 
 topographic variations on | 
| 285 | 
 internal wave breaking - the cross-slope velocity is in color, the density | 
 internal wave breaking - the cross-slope velocity is in color, the density | 
| 286 | 
 contoured. The internal waves are excited by application of open boundary | 
 contoured. The internal waves are excited by application of open boundary | 
| 287 | 
 conditions on the left.\ They propagate to the sloping boundary (represented | 
 conditions on the left. They propagate to the sloping boundary (represented | 
| 288 | 
 using MITgcm's finite volume spatial discretization) where they break under | 
 using MITgcm's finite volume spatial discretization) where they break under | 
| 289 | 
 nonhydrostatic dynamics. | 
 nonhydrostatic dynamics. | 
| 290 | 
  | 
  | 
| 293 | 
 %%CNHend | 
 %%CNHend | 
| 294 | 
  | 
  | 
| 295 | 
 \subsection{Parameter sensitivity using the adjoint of MITgcm} | 
 \subsection{Parameter sensitivity using the adjoint of MITgcm} | 
| 296 | 
  | 
 \begin{rawhtml} | 
| 297 | 
  | 
 <!-- CMIREDIR:parameter_sensitivity: --> | 
| 298 | 
  | 
 \end{rawhtml} | 
| 299 | 
  | 
  | 
| 300 | 
 Forward and tangent linear counterparts of MITgcm are supported using an | 
 Forward and tangent linear counterparts of MITgcm are supported using an | 
| 301 | 
 `automatic adjoint compiler'. These can be used in parameter sensitivity and | 
 `automatic adjoint compiler'. These can be used in parameter sensitivity and | 
| 302 | 
 data assimilation studies. | 
 data assimilation studies. | 
| 303 | 
  | 
  | 
| 304 | 
 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} | 
| 305 | 
 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 | 
| 306 | 
 of the overturning streamfunction shown in fig?.? at 40$^{\circ }$N and $% | 
 of the overturning stream-function shown in figure \ref{fig:large-scale-circ} | 
| 307 | 
 \mathcal{H}$ is the air-sea heat flux 100 years before. We see that $J$ is | 
 at 60$^{\circ }$N and $ | 
| 308 | 
  | 
 \mathcal{H}(\lambda,\varphi)$ is the mean, local air-sea heat flux over | 
| 309 | 
  | 
 a 100 year period. We see that $J$ is | 
| 310 | 
 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 | 
| 311 | 
 of deep water for the thermohaline circulations. This calculation also | 
 of deep water for the thermohaline circulations. This calculation also | 
| 312 | 
 yields sensitivities to all other model parameters. | 
 yields sensitivities to all other model parameters. | 
| 316 | 
 %%CNHend | 
 %%CNHend | 
| 317 | 
  | 
  | 
| 318 | 
 \subsection{Global state estimation of the ocean} | 
 \subsection{Global state estimation of the ocean} | 
| 319 | 
  | 
 \begin{rawhtml} | 
| 320 | 
  | 
 <!-- CMIREDIR:global_state_estimation: --> | 
| 321 | 
  | 
 \end{rawhtml} | 
| 322 | 
  | 
  | 
| 323 | 
  | 
  | 
| 324 | 
 An important application of MITgcm is in state estimation of the global | 
 An important application of MITgcm is in state estimation of the global | 
| 325 | 
 ocean circulation. An appropriately defined `cost function', which measures | 
 ocean circulation. An appropriately defined `cost function', which measures | 
| 326 | 
 the departure of the model from observations (both remotely sensed and | 
 the departure of the model from observations (both remotely sensed and | 
| 327 | 
 insitu) over an interval of time, is minimized by adjusting `control | 
 in-situ) over an interval of time, is minimized by adjusting `control | 
| 328 | 
 parameters' such as air-sea fluxes, the wind field, the initial conditions | 
 parameters' such as air-sea fluxes, the wind field, the initial conditions | 
| 329 | 
 etc. Figure ?.? shows an estimate of the time-mean surface elevation of the | 
 etc. Figure \ref{fig:assimilated-globes} shows the large scale planetary | 
| 330 | 
 ocean obtained by bringing the model in to consistency with altimetric and | 
 circulation and a Hopf-Muller plot of Equatorial sea-surface height. | 
| 331 | 
 in-situ observations over the period 1992-1997. | 
 Both are obtained from assimilation bringing the model in to | 
| 332 | 
  | 
 consistency with altimetric and in-situ observations over the period | 
| 333 | 
  | 
 1992-1997. | 
| 334 | 
  | 
  | 
| 335 | 
 %% CNHbegin | 
 %% CNHbegin | 
| 336 | 
 \input{part1/globes_figure} | 
 \input{part1/assim_figure} | 
| 337 | 
 %% CNHend | 
 %% CNHend | 
| 338 | 
  | 
  | 
| 339 | 
 \subsection{Ocean biogeochemical cycles} | 
 \subsection{Ocean biogeochemical cycles} | 
| 340 | 
  | 
 \begin{rawhtml} | 
| 341 | 
  | 
 <!-- CMIREDIR:ocean_biogeo_cycles: --> | 
| 342 | 
  | 
 \end{rawhtml} | 
| 343 | 
  | 
  | 
| 344 | 
 MITgcm is being used to study global biogeochemical cycles in the ocean. For | 
 MITgcm is being used to study global biogeochemical cycles in the ocean. For | 
| 345 | 
 example one can study the effects of interannual changes in meteorological | 
 example one can study the effects of interannual changes in meteorological | 
| 346 | 
 forcing and upper ocean circulation on the fluxes of carbon dioxide and | 
 forcing and upper ocean circulation on the fluxes of carbon dioxide and | 
| 347 | 
 oxygen between the ocean and atmosphere. The figure shows the annual air-sea | 
 oxygen between the ocean and atmosphere. Figure \ref{fig:biogeo} shows  | 
| 348 | 
 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  | 
| 349 | 
 from a single year of a global, interannually varying simulation. | 
 the southern oceans from a single year of a global, interannually varying  | 
| 350 | 
  | 
 simulation. The simulation is run at $1^{\circ}\times1^{\circ}$ resolution | 
| 351 | 
  | 
 telescoping to $\frac{1}{3}^{\circ}\times\frac{1}{3}^{\circ}$ in the tropics (not shown). | 
| 352 | 
  | 
  | 
| 353 | 
 %%CNHbegin | 
 %%CNHbegin | 
| 354 | 
 \input{part1/biogeo_figure} | 
 \input{part1/biogeo_figure} | 
| 355 | 
 %%CNHend | 
 %%CNHend | 
| 356 | 
  | 
  | 
| 357 | 
 \subsection{Simulations of laboratory experiments} | 
 \subsection{Simulations of laboratory experiments} | 
| 358 | 
  | 
 \begin{rawhtml} | 
| 359 | 
  | 
 <!-- CMIREDIR:classroom_exp: --> | 
| 360 | 
  | 
 \end{rawhtml} | 
| 361 | 
  | 
  | 
| 362 | 
 Figure ?.? shows MITgcm being used to simulate a laboratory experiment | 
 Figure \ref{fig:lab-simulation} shows MITgcm being used to simulate a  | 
| 363 | 
 enquiring in to the dynamics of the Antarctic Circumpolar Current (ACC). An | 
 laboratory experiment inquiring into the dynamics of the Antarctic Circumpolar Current (ACC). An | 
| 364 | 
 initially homogeneous tank of water ($1m$ in diameter) is driven from its | 
 initially homogeneous tank of water ($1m$ in diameter) is driven from its | 
| 365 | 
 free surface by a rotating heated disk. The combined action of mechanical | 
 free surface by a rotating heated disk. The combined action of mechanical | 
| 366 | 
 and thermal forcing creates a lens of fluid which becomes baroclinically | 
 and thermal forcing creates a lens of fluid which becomes baroclinically | 
| 367 | 
 unstable. The stratification and depth of penetration of the lens is | 
 unstable. The stratification and depth of penetration of the lens is | 
| 368 | 
 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 | 
| 369 | 
 stratification of the ACC. | 
 stratification of the ACC. | 
| 370 | 
  | 
  | 
| 371 | 
 %%CNHbegin | 
 %%CNHbegin | 
| 376 | 
 % $Name$ | 
 % $Name$ | 
| 377 | 
  | 
  | 
| 378 | 
 \section{Continuous equations in `r' coordinates} | 
 \section{Continuous equations in `r' coordinates} | 
| 379 | 
  | 
 \begin{rawhtml} | 
| 380 | 
  | 
 <!-- CMIREDIR:z-p_isomorphism: --> | 
| 381 | 
  | 
 \end{rawhtml} | 
| 382 | 
  | 
  | 
| 383 | 
 To render atmosphere and ocean models from one dynamical core we exploit | 
 To render atmosphere and ocean models from one dynamical core we exploit | 
| 384 | 
 `isomorphisms' between equation sets that govern the evolution of the | 
 `isomorphisms' between equation sets that govern the evolution of the | 
| 385 | 
 respective fluids - see fig.4% | 
 respective fluids - see figure \ref{fig:isomorphic-equations}.  | 
| 386 | 
 \marginpar{ | 
 One system of hydrodynamical equations is written down | 
 | 
 Fig.4. Isomorphisms}. One system of hydrodynamical equations is written down | 
  | 
| 387 | 
 and encoded. The model variables have different interpretations depending on | 
 and encoded. The model variables have different interpretations depending on | 
| 388 | 
 whether the atmosphere or ocean is being studied. Thus, for example, the | 
 whether the atmosphere or ocean is being studied. Thus, for example, the | 
| 389 | 
 vertical coordinate `$r$' is interpreted as pressure, $p$, if we are | 
 vertical coordinate `$r$' is interpreted as pressure, $p$, if we are | 
| 390 | 
 modeling the atmosphere and height, $z$, if we are modeling the ocean. | 
 modeling the atmosphere (right hand side of figure \ref{fig:isomorphic-equations}) | 
| 391 | 
  | 
 and height, $z$, if we are modeling the ocean (left hand side of figure | 
| 392 | 
  | 
 \ref{fig:isomorphic-equations}). | 
| 393 | 
  | 
  | 
| 394 | 
 %%CNHbegin | 
 %%CNHbegin | 
| 395 | 
 \input{part1/zandpcoord_figure.tex} | 
 \input{part1/zandpcoord_figure.tex} | 
| 401 | 
 depend on $\theta $, $S$, and $p$. The equations that govern the evolution | 
 depend on $\theta $, $S$, and $p$. The equations that govern the evolution | 
| 402 | 
 of these fields, obtained by applying the laws of classical mechanics and | 
 of these fields, obtained by applying the laws of classical mechanics and | 
| 403 | 
 thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of | 
 thermodynamics to a Boussinesq, Navier-Stokes fluid are, written in terms of | 
| 404 | 
 a generic vertical coordinate, $r$, see fig.5% | 
 a generic vertical coordinate, $r$, so that the appropriate | 
| 405 | 
 \marginpar{ | 
 kinematic boundary conditions can be applied isomorphically | 
| 406 | 
 Fig.5 The vertical coordinate of model}: | 
 see figure \ref{fig:zandp-vert-coord}. | 
| 407 | 
  | 
  | 
| 408 | 
 %%CNHbegin | 
 %%CNHbegin | 
| 409 | 
 \input{part1/vertcoord_figure.tex} | 
 \input{part1/vertcoord_figure.tex} | 
| 410 | 
 %%CNHend | 
 %%CNHend | 
| 411 | 
  | 
  | 
| 412 | 
 \begin{equation*} | 
 \begin{equation} | 
| 413 | 
 \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}} | 
| 414 | 
 \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}}% | 
 \right) _{h}+\mathbf{\nabla }_{h}\phi =\mathcal{F}_{\vec{\mathbf{v}_{h}}} | 
| 415 | 
 \text{ horizontal mtm} | 
 \text{ horizontal mtm} \label{eq:horizontal_mtm} | 
| 416 | 
 \end{equation*} | 
 \end{equation} | 
| 417 | 
  | 
  | 
| 418 | 
 \begin{equation*} | 
 \begin{equation} | 
| 419 | 
 \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{ | 
| 420 | 
 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{ | 
| 421 | 
 vertical mtm} | 
 vertical mtm} \label{eq:vertical_mtm} | 
| 422 | 
 \end{equation*} | 
 \end{equation} | 
| 423 | 
  | 
  | 
| 424 | 
 \begin{equation} | 
 \begin{equation} | 
| 425 | 
 \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{% | 
 \mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \dot{r}}{ | 
| 426 | 
 \partial r}=0\text{ continuity}  \label{eq:continuous} | 
 \partial r}=0\text{ continuity}  \label{eq:continuity} | 
| 427 | 
 \end{equation} | 
 \end{equation} | 
| 428 | 
  | 
  | 
| 429 | 
 \begin{equation*} | 
 \begin{equation} | 
| 430 | 
 b=b(\theta ,S,r)\text{ equation of state} | 
 b=b(\theta ,S,r)\text{ equation of state} \label{eq:equation_of_state} | 
| 431 | 
 \end{equation*} | 
 \end{equation} | 
| 432 | 
  | 
  | 
| 433 | 
 \begin{equation*} | 
 \begin{equation} | 
| 434 | 
 \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature} | 
 \frac{D\theta }{Dt}=\mathcal{Q}_{\theta }\text{ potential temperature} | 
| 435 | 
 \end{equation*} | 
 \label{eq:potential_temperature} | 
| 436 | 
  | 
 \end{equation} | 
| 437 | 
  | 
  | 
| 438 | 
 \begin{equation*} | 
 \begin{equation} | 
| 439 | 
 \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity} | 
 \frac{DS}{Dt}=\mathcal{Q}_{S}\text{ humidity/salinity} | 
| 440 | 
 \end{equation*} | 
 \label{eq:humidity_salt} | 
| 441 | 
  | 
 \end{equation} | 
| 442 | 
  | 
  | 
| 443 | 
 Here: | 
 Here: | 
| 444 | 
  | 
  | 
| 452 | 
 \end{equation*} | 
 \end{equation*} | 
| 453 | 
  | 
  | 
| 454 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 455 | 
 \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r}% | 
 \mathbf{\nabla }=\mathbf{\nabla }_{h}+\widehat{k}\frac{\partial }{\partial r} | 
| 456 | 
 \text{ is the `grad' operator} | 
 \text{ is the `grad' operator} | 
| 457 | 
 \end{equation*} | 
 \end{equation*} | 
| 458 | 
 with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k}% | 
 with $\mathbf{\nabla }_{h}$ operating in the horizontal and $\widehat{k} | 
| 459 | 
 \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$ | 
 \frac{\partial }{\partial r}$ operating in the vertical, where $\widehat{k}$ | 
| 460 | 
 is a unit vector in the vertical | 
 is a unit vector in the vertical | 
| 461 | 
  | 
  | 
| 489 | 
 \end{equation*} | 
 \end{equation*} | 
| 490 | 
  | 
  | 
| 491 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 492 | 
 \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{% | 
 \mathcal{F}_{\vec{\mathbf{v}}}\text{ are forcing and dissipation of }\vec{ | 
| 493 | 
 \mathbf{v}} | 
 \mathbf{v}} | 
| 494 | 
 \end{equation*} | 
 \end{equation*} | 
| 495 | 
  | 
  | 
| 502 | 
 \end{equation*} | 
 \end{equation*} | 
| 503 | 
  | 
  | 
| 504 | 
 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 | 
| 505 | 
 extensive `physics' packages for atmosphere and ocean described in Chapter 6. | 
 `physics' and forcing packages for atmosphere and ocean. These are described | 
| 506 | 
  | 
 in later chapters. | 
| 507 | 
  | 
  | 
| 508 | 
 \subsection{Kinematic Boundary conditions} | 
 \subsection{Kinematic Boundary conditions} | 
| 509 | 
  | 
  | 
| 510 | 
 \subsubsection{vertical} | 
 \subsubsection{vertical} | 
| 511 | 
  | 
  | 
| 512 | 
 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}): | 
| 513 | 
  | 
  | 
| 514 | 
 \begin{equation} | 
 \begin{equation} | 
| 515 | 
 \dot{r}=0atr=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)} | 
 \dot{r}=0 \text{\ at\ } r=R_{fixed}(x,y)\text{ (ocean bottom, top of the atmosphere)} | 
| 516 | 
 \label{eq:fixedbc} | 
 \label{eq:fixedbc} | 
| 517 | 
 \end{equation} | 
 \end{equation} | 
| 518 | 
  | 
  | 
| 519 | 
 \begin{equation} | 
 \begin{equation} | 
| 520 | 
 \dot{r}=\frac{Dr}{Dt}atr=R_{moving}\text{ \ | 
 \dot{r}=\frac{Dr}{Dt} \text{\ at\ } r=R_{moving}\text{ \ | 
| 521 | 
 (oceansurface,bottomoftheatmosphere)}  \label{eq:movingbc} | 
 (ocean surface,bottom of the atmosphere)}  \label{eq:movingbc} | 
| 522 | 
 \end{equation} | 
 \end{equation} | 
| 523 | 
  | 
  | 
| 524 | 
 Here | 
 Here | 
| 535 | 
  | 
  | 
| 536 | 
 \begin{equation} | 
 \begin{equation} | 
| 537 | 
 \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow} | 
 \vec{\mathbf{v}}\cdot \vec{\mathbf{n}}=0  \label{eq:noflow} | 
| 538 | 
 \end{equation}% | 
 \end{equation} | 
| 539 | 
 where $\vec{\mathbf{n}}$ is the normal to a solid boundary. | 
 where $\vec{\mathbf{n}}$ is the normal to a solid boundary. | 
| 540 | 
  | 
  | 
| 541 | 
 \subsection{Atmosphere} | 
 \subsection{Atmosphere} | 
| 542 | 
  | 
  | 
| 543 | 
 In the atmosphere, see fig.5, we interpret: | 
 In the atmosphere, (see figure \ref{fig:zandp-vert-coord}), we interpret: | 
| 544 | 
  | 
  | 
| 545 | 
 \begin{equation} | 
 \begin{equation} | 
| 546 | 
 r=p\text{ is the pressure}  \label{eq:atmos-r} | 
 r=p\text{ is the pressure}  \label{eq:atmos-r} | 
| 572 | 
  | 
  | 
| 573 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 574 | 
 T\text{ is absolute temperature} | 
 T\text{ is absolute temperature} | 
| 575 | 
 \end{equation*}% | 
 \end{equation*} | 
| 576 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 577 | 
 p\text{ is the pressure} | 
 p\text{ is the pressure} | 
| 578 | 
 \end{equation*}% | 
 \end{equation*} | 
| 579 | 
 \begin{eqnarray*} | 
 \begin{eqnarray*} | 
| 580 | 
 &&z\text{ is the height of the pressure surface} \\ | 
 &&z\text{ is the height of the pressure surface} \\ | 
| 581 | 
 &&g\text{ is the acceleration due to gravity} | 
 &&g\text{ is the acceleration due to gravity} | 
| 585 | 
 the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  | 
 the Exner function $\Pi (p)$ given by (see Appendix Atmosphere)  | 
| 586 | 
 \begin{equation} | 
 \begin{equation} | 
| 587 | 
 \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner} | 
 \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{eq:exner} | 
| 588 | 
 \end{equation}% | 
 \end{equation} | 
| 589 | 
 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 | 
| 590 | 
 constant and $c_{p}$ the specific heat of air at constant pressure. | 
 constant and $c_{p}$ the specific heat of air at constant pressure. | 
| 591 | 
  | 
  | 
| 611 | 
 atmosphere)}  \label{eq:moving-bc-atmos} | 
 atmosphere)}  \label{eq:moving-bc-atmos} | 
| 612 | 
 \end{eqnarray} | 
 \end{eqnarray} | 
| 613 | 
  | 
  | 
| 614 | 
 Then the (hydrostatic form of) eq(\ref{eq:continuous}) yields a consistent | 
 Then the (hydrostatic form of) equations | 
| 615 | 
 set of atmospheric equations which, for convenience, are written out in $p$ | 
 (\ref{eq:horizontal_mtm}-\ref{eq:humidity_salt}) yields a consistent | 
| 616 | 
 coordinates in Appendix Atmosphere - see eqs(\ref{eq:atmos-prime}). | 
 set of atmospheric equations which, for convenience, are written out | 
| 617 | 
  | 
 in $p$ coordinates in Appendix Atmosphere - see | 
| 618 | 
  | 
 eqs(\ref{eq:atmos-prime}). | 
| 619 | 
  | 
  | 
| 620 | 
 \subsection{Ocean} | 
 \subsection{Ocean} | 
| 621 | 
  | 
  | 
| 637 | 
  | 
  | 
| 638 | 
 The surface of the ocean is given by: $R_{moving}=\eta $ | 
 The surface of the ocean is given by: $R_{moving}=\eta $ | 
| 639 | 
  | 
  | 
| 640 | 
 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 $ | 
| 641 | 
 R_{o}=Z_{o}=0$. | 
 R_{o}=Z_{o}=0$. | 
| 642 | 
  | 
  | 
| 643 | 
 Boundary conditions are: | 
 Boundary conditions are: | 
| 645 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 646 | 
 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} | 
| 647 | 
 \\ | 
 \\ | 
| 648 | 
 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)  | 
| 649 | 
 \label{eq:moving-bc-ocean}} | 
 \label{eq:moving-bc-ocean}} | 
| 650 | 
 \end{eqnarray} | 
 \end{eqnarray} | 
| 651 | 
 where $\eta $ is the elevation of the free surface. | 
 where $\eta $ is the elevation of the free surface. | 
| 652 | 
  | 
  | 
| 653 | 
 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  | 
| 654 | 
  | 
 of oceanic equations | 
| 655 | 
 which, for convenience, are written out in $z$ coordinates in Appendix Ocean | 
 which, for convenience, are written out in $z$ coordinates in Appendix Ocean | 
| 656 | 
 - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}). | 
 - see eqs(\ref{eq:ocean-mom}) to (\ref{eq:ocean-salt}). | 
| 657 | 
  | 
  | 
| 658 | 
 \subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and | 
 \subsection{Hydrostatic, Quasi-hydrostatic, Quasi-nonhydrostatic and | 
| 659 | 
 Non-hydrostatic forms} | 
 Non-hydrostatic forms} | 
| 660 | 
  | 
 \begin{rawhtml} | 
| 661 | 
  | 
 <!-- CMIREDIR:non_hydrostatic: --> | 
| 662 | 
  | 
 \end{rawhtml} | 
| 663 | 
  | 
  | 
| 664 | 
  | 
  | 
| 665 | 
 Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms: | 
 Let us separate $\phi $ in to surface, hydrostatic and non-hydrostatic terms: | 
| 666 | 
  | 
  | 
| 667 | 
 \begin{equation} | 
 \begin{equation} | 
| 668 | 
 \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) | 
| 669 | 
 \label{eq:phi-split} | 
 \label{eq:phi-split} | 
| 670 | 
 \end{equation}% | 
 \end{equation} | 
| 671 | 
 and write eq(\ref{incompressible}a,b) in the form: | 
 %and write eq(\ref{eq:incompressible}) in the form:  | 
| 672 | 
  | 
 %                  ^- this eq is missing (jmc) ; replaced with: | 
| 673 | 
  | 
 and write eq( \ref{eq:horizontal_mtm}) in the form: | 
| 674 | 
  | 
  | 
| 675 | 
 \begin{equation} | 
 \begin{equation} | 
| 676 | 
 \frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi | 
 \frac{\partial \vec{\mathbf{v}_{h}}}{\partial t}+\mathbf{\nabla }_{h}\phi | 
| 683 | 
 \end{equation} | 
 \end{equation} | 
| 684 | 
  | 
  | 
| 685 | 
 \begin{equation} | 
 \begin{equation} | 
| 686 | 
 \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{% | 
 \epsilon _{nh}\frac{\partial \dot{r}}{\partial t}+\frac{\partial \phi _{nh}}{ | 
| 687 | 
 \partial r}=G_{\dot{r}}  \label{eq:mom-w} | 
 \partial r}=G_{\dot{r}}  \label{eq:mom-w} | 
| 688 | 
 \end{equation} | 
 \end{equation} | 
| 689 | 
 Here $\epsilon _{nh}$ is a non-hydrostatic parameter. | 
 Here $\epsilon _{nh}$ is a non-hydrostatic parameter. | 
| 690 | 
  | 
  | 
| 691 | 
 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 | 
| 692 | 
 {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 | 
| 693 | 
 terms in the momentum equations. In spherical coordinates they take the form% | 
 terms in the momentum equations. In spherical coordinates they take the form | 
| 694 | 
 \footnote{% | 
 \footnote{ | 
| 695 | 
 In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms | 
 In the hydrostatic primitive equations (\textbf{HPE}) all underlined terms | 
| 696 | 
 in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref% | 
 in (\ref{eq:gu-speherical}), (\ref{eq:gv-spherical}) and (\ref | 
| 697 | 
 {eq:gw-spherical}) are omitted; the singly-underlined terms are included in | 
 {eq:gw-spherical}) are omitted; the singly-underlined terms are included in | 
| 698 | 
 the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model (% | 
 the quasi-hydrostatic model (\textbf{QH}). The fully non-hydrostatic model ( | 
| 699 | 
 \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 | 
| 700 | 
 discussion: | 
 discussion: | 
| 701 | 
  | 
  | 
| 703 | 
 \left.  | 
 \left.  | 
| 704 | 
 \begin{tabular}{l} | 
 \begin{tabular}{l} | 
| 705 | 
 $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  | 
 $G_{u}=-\vec{\mathbf{v}}.\nabla u$ \\  | 
| 706 | 
 $-\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\} $ | 
| 707 | 
 \\  | 
 \\  | 
| 708 | 
 $-\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\} $ | 
| 709 | 
 \\  | 
 \\  | 
| 710 | 
 $+\mathcal{F}_{u}$% | 
 $+\mathcal{F}_{u}$ | 
| 711 | 
 \end{tabular}% | 
 \end{tabular} | 
| 712 | 
 \ \right\} \left\{  | 
 \ \right\} \left\{  | 
| 713 | 
 \begin{tabular}{l} | 
 \begin{tabular}{l} | 
| 714 | 
 \textit{advection} \\  | 
 \textit{advection} \\  | 
| 715 | 
 \textit{metric} \\  | 
 \textit{metric} \\  | 
| 716 | 
 \textit{Coriolis} \\  | 
 \textit{Coriolis} \\  | 
| 717 | 
 \textit{\ Forcing/Dissipation}% | 
 \textit{\ Forcing/Dissipation} | 
| 718 | 
 \end{tabular}% | 
 \end{tabular} | 
| 719 | 
 \ \right. \qquad  \label{eq:gu-speherical} | 
 \ \right. \qquad  \label{eq:gu-speherical} | 
| 720 | 
 \end{equation} | 
 \end{equation} | 
| 721 | 
  | 
  | 
| 723 | 
 \left.  | 
 \left.  | 
| 724 | 
 \begin{tabular}{l} | 
 \begin{tabular}{l} | 
| 725 | 
 $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  | 
 $G_{v}=-\vec{\mathbf{v}}.\nabla v$ \\  | 
| 726 | 
 $-\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\}  | 
| 727 | 
 $ \\  | 
 $ \\  | 
| 728 | 
 $-\left\{ -2\Omega u\sin lat\right\} $ \\  | 
 $-\left\{ -2\Omega u\sin \varphi \right\} $ \\  | 
| 729 | 
 $+\mathcal{F}_{v}$% | 
 $+\mathcal{F}_{v}$ | 
| 730 | 
 \end{tabular}% | 
 \end{tabular} | 
| 731 | 
 \ \right\} \left\{  | 
 \ \right\} \left\{  | 
| 732 | 
 \begin{tabular}{l} | 
 \begin{tabular}{l} | 
| 733 | 
 \textit{advection} \\  | 
 \textit{advection} \\  | 
| 734 | 
 \textit{metric} \\  | 
 \textit{metric} \\  | 
| 735 | 
 \textit{Coriolis} \\  | 
 \textit{Coriolis} \\  | 
| 736 | 
 \textit{\ Forcing/Dissipation}% | 
 \textit{\ Forcing/Dissipation} | 
| 737 | 
 \end{tabular}% | 
 \end{tabular} | 
| 738 | 
 \ \right. \qquad  \label{eq:gv-spherical} | 
 \ \right. \qquad  \label{eq:gv-spherical} | 
| 739 | 
 \end{equation}% | 
 \end{equation} | 
| 740 | 
 \qquad \qquad \qquad \qquad \qquad | 
 \qquad \qquad \qquad \qquad \qquad | 
| 741 | 
  | 
  | 
| 742 | 
 \begin{equation} | 
 \begin{equation} | 
| 744 | 
 \begin{tabular}{l} | 
 \begin{tabular}{l} | 
| 745 | 
 $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  | 
 $G_{\dot{r}}=-\underline{\underline{\vec{\mathbf{v}}.\nabla \dot{r}}}$ \\  | 
| 746 | 
 $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  | 
 $+\left\{ \underline{\frac{u^{_{^{2}}}+v^{2}}{{r}}}\right\} $ \\  | 
| 747 | 
 ${+}\underline{{2\Omega u\cos lat}}$ \\  | 
 ${+}\underline{{2\Omega u\cos \varphi}}$ \\  | 
| 748 | 
 $\underline{\underline{\mathcal{F}_{\dot{r}}}}$% | 
 $\underline{\underline{\mathcal{F}_{\dot{r}}}}$ | 
| 749 | 
 \end{tabular}% | 
 \end{tabular} | 
| 750 | 
 \ \right\} \left\{  | 
 \ \right\} \left\{  | 
| 751 | 
 \begin{tabular}{l} | 
 \begin{tabular}{l} | 
| 752 | 
 \textit{advection} \\  | 
 \textit{advection} \\  | 
| 753 | 
 \textit{metric} \\  | 
 \textit{metric} \\  | 
| 754 | 
 \textit{Coriolis} \\  | 
 \textit{Coriolis} \\  | 
| 755 | 
 \textit{\ Forcing/Dissipation}% | 
 \textit{\ Forcing/Dissipation} | 
| 756 | 
 \end{tabular}% | 
 \end{tabular} | 
| 757 | 
 \ \right.  \label{eq:gw-spherical} | 
 \ \right.  \label{eq:gw-spherical} | 
| 758 | 
 \end{equation}% | 
 \end{equation} | 
| 759 | 
 \qquad \qquad \qquad \qquad \qquad | 
 \qquad \qquad \qquad \qquad \qquad | 
| 760 | 
  | 
  | 
| 761 | 
 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 `$\varphi$ | 
| 762 | 
 ' is latitude. | 
 ' is latitude. | 
| 763 | 
  | 
  | 
| 764 | 
 Grad and div operators in spherical coordinates are defined in appendix | 
 Grad and div operators in spherical coordinates are defined in appendix | 
| 765 | 
 OPERATORS.% | 
 OPERATORS. | 
 | 
 \marginpar{ | 
  | 
 | 
 Fig.6 Spherical polar coordinate system.} | 
  | 
| 766 | 
  | 
  | 
| 767 | 
 %%CNHbegin | 
 %%CNHbegin | 
| 768 | 
 \input{part1/sphere_coord_figure.tex} | 
 \input{part1/sphere_coord_figure.tex} | 
| 770 | 
  | 
  | 
| 771 | 
 \subsubsection{Shallow atmosphere approximation} | 
 \subsubsection{Shallow atmosphere approximation} | 
| 772 | 
  | 
  | 
| 773 | 
 Most models are based on the `hydrostatic primitive equations' (HPE's) in | 
 Most models are based on the `hydrostatic primitive equations' (HPE's) | 
| 774 | 
 which the vertical momentum equation is reduced to a statement of | 
 in which the vertical momentum equation is reduced to a statement of | 
| 775 | 
 hydrostatic balance and the `traditional approximation' is made in which the | 
 hydrostatic balance and the `traditional approximation' is made in | 
| 776 | 
 Coriolis force is treated approximately and the shallow atmosphere | 
 which the Coriolis force is treated approximately and the shallow | 
| 777 | 
 approximation is made.\ The MITgcm need not make the `traditional | 
 atmosphere approximation is made.  MITgcm need not make the | 
| 778 | 
 approximation'. To be able to support consistent non-hydrostatic forms the | 
 `traditional approximation'. To be able to support consistent | 
| 779 | 
 shallow atmosphere approximation can be relaxed - when dividing through by $% | 
 non-hydrostatic forms the shallow atmosphere approximation can be | 
| 780 | 
 r $ in, for example, (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, | 
 relaxed - when dividing through by $ r $ in, for example, | 
| 781 | 
 the radius of the earth. | 
 (\ref{eq:gu-speherical}), we do not replace $r$ by $a$, the radius of | 
| 782 | 
  | 
 the earth. | 
| 783 | 
  | 
  | 
| 784 | 
 \subsubsection{Hydrostatic and quasi-hydrostatic forms} | 
 \subsubsection{Hydrostatic and quasi-hydrostatic forms} | 
| 785 | 
  | 
 \label{sec:hydrostatic_and_quasi-hydrostatic_forms} | 
| 786 | 
  | 
  | 
| 787 | 
 These are discussed at length in Marshall et al (1997a). | 
 These are discussed at length in Marshall et al (1997a). | 
| 788 | 
  | 
  | 
| 791 | 
 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 | 
| 792 | 
 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 | 
| 793 | 
 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 | 
| 794 | 
 computed at all other levels by integration of the hydrostatic relation, eq(% | 
 computed at all other levels by integration of the hydrostatic relation, eq( | 
| 795 | 
 \ref{eq:hydrostatic}). | 
 \ref{eq:hydrostatic}). | 
| 796 | 
  | 
  | 
| 797 | 
 In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between | 
 In the `quasi-hydrostatic' equations (\textbf{QH)} strict balance between | 
| 798 | 
 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 | 
| 799 | 
 \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 | 
| 800 | 
 contribution to the pressure field: only the terms underlined twice in Eqs. (% | 
 contribution to the pressure field: only the terms underlined twice in Eqs. ( | 
| 801 | 
 \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 | 
| 802 | 
 and, simultaneously, the shallow atmosphere approximation is relaxed. In  | 
 and, simultaneously, the shallow atmosphere approximation is relaxed. In  | 
| 803 | 
 \textbf{QH}\ \textit{all} the metric terms are retained and the full | 
 \textbf{QH}\ \textit{all} the metric terms are retained and the full | 
| 805 | 
 vertical momentum equation (\ref{eq:mom-w}) becomes: | 
 vertical momentum equation (\ref{eq:mom-w}) becomes: | 
| 806 | 
  | 
  | 
| 807 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 808 | 
 \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos lat | 
 \frac{\partial \phi _{nh}}{\partial r}=2\Omega u\cos \varphi | 
| 809 | 
 \end{equation*} | 
 \end{equation*} | 
| 810 | 
 making a small correction to the hydrostatic pressure. | 
 making a small correction to the hydrostatic pressure. | 
| 811 | 
  | 
  | 
| 816 | 
  | 
  | 
| 817 | 
 \subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} | 
 \subsubsection{Non-hydrostatic and quasi-nonhydrostatic forms} | 
| 818 | 
  | 
  | 
| 819 | 
 The MIT model presently supports a full non-hydrostatic ocean isomorph, but | 
 MITgcm presently supports a full non-hydrostatic ocean isomorph, but | 
| 820 | 
 only a quasi-non-hydrostatic atmospheric isomorph. | 
 only a quasi-non-hydrostatic atmospheric isomorph. | 
| 821 | 
  | 
  | 
| 822 | 
 \paragraph{Non-hydrostatic Ocean} | 
 \paragraph{Non-hydrostatic Ocean} | 
| 823 | 
  | 
  | 
| 824 | 
 In the non-hydrostatic ocean model all terms in equations Eqs.(\ref% | 
 In the non-hydrostatic ocean model all terms in equations Eqs.(\ref | 
| 825 | 
 {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A | 
 {eq:gu-speherical} $\rightarrow $\ \ref{eq:gw-spherical}) are retained. A | 
| 826 | 
 three dimensional elliptic equation must be solved subject to Neumann | 
 three dimensional elliptic equation must be solved subject to Neumann | 
| 827 | 
 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 | 
| 828 | 
 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 | 
| 829 | 
 incompressible condition eq(\ref{eq:continuous})c has already filtered out | 
 incompressible condition eq(\ref{eq:continuity}) has already filtered out | 
| 830 | 
 acoustic modes. It does, however, ensure that the gravity waves are treated | 
 acoustic modes. It does, however, ensure that the gravity waves are treated | 
| 831 | 
 accurately with an exact dispersion relation. The \textbf{NH} set has a | 
 accurately with an exact dispersion relation. The \textbf{NH} set has a | 
| 832 | 
 complete angular momentum principle and consistent energetics - see White | 
 complete angular momentum principle and consistent energetics - see White | 
| 834 | 
  | 
  | 
| 835 | 
 \paragraph{Quasi-nonhydrostatic Atmosphere} | 
 \paragraph{Quasi-nonhydrostatic Atmosphere} | 
| 836 | 
  | 
  | 
| 837 | 
 In the non-hydrostatic version of our atmospheric model we approximate $\dot{% | 
 In the non-hydrostatic version of our atmospheric model we approximate $\dot{ | 
| 838 | 
 r}$ 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}) | 
| 839 | 
 (but only here) by: | 
 (but only here) by: | 
| 840 | 
  | 
  | 
| 841 | 
 \begin{equation} | 
 \begin{equation} | 
| 842 | 
 \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} | 
| 843 | 
 \end{equation}% | 
 \end{equation} | 
| 844 | 
 where $p_{hy}$ is the hydrostatic pressure. | 
 where $p_{hy}$ is the hydrostatic pressure. | 
| 845 | 
  | 
  | 
| 846 | 
 \subsubsection{Summary of equation sets supported by model} | 
 \subsubsection{Summary of equation sets supported by model} | 
| 868 | 
  | 
  | 
| 869 | 
 \subparagraph{Non-hydrostatic} | 
 \subparagraph{Non-hydrostatic} | 
| 870 | 
  | 
  | 
| 871 | 
 Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$% | 
 Non-hydrostatic forms of the incompressible Boussinesq equations in $z-$ | 
| 872 | 
 coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref% | 
 coordinates are supported - see eqs(\ref{eq:ocean-mom}) to (\ref | 
| 873 | 
 {eq:ocean-salt}). | 
 {eq:ocean-salt}). | 
| 874 | 
  | 
  | 
| 875 | 
 \subsection{Solution strategy} | 
 \subsection{Solution strategy} | 
| 876 | 
  | 
  | 
| 877 | 
 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{ | 
| 878 | 
 NH} models is summarized in Fig.7.% | 
 NH} models is summarized in Figure \ref{fig:solution-strategy}. | 
| 879 | 
 \marginpar{ | 
 Under all dynamics, a 2-d elliptic equation is | 
 | 
 Fig.7 Solution strategy} Under all dynamics, a 2-d elliptic equation is | 
  | 
| 880 | 
 first solved to find the surface pressure and the hydrostatic pressure at | 
 first solved to find the surface pressure and the hydrostatic pressure at | 
| 881 | 
 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  | 
| 882 | 
 \textbf{QH} dynamics, the horizontal momentum equations are then stepped | 
 \textbf{QH} dynamics, the horizontal momentum equations are then stepped | 
| 890 | 
 %%CNHend | 
 %%CNHend | 
| 891 | 
  | 
  | 
| 892 | 
 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 | 
| 893 | 
 course, some complication that goes with the inclusion of $\cos \phi \ $% | 
 course, some complication that goes with the inclusion of $\cos \varphi \ $ | 
| 894 | 
 Coriolis terms and the relaxation of the shallow atmosphere approximation. | 
 Coriolis terms and the relaxation of the shallow atmosphere approximation. | 
| 895 | 
 But this leads to negligible increase in computation. In \textbf{NH}, in | 
 But this leads to negligible increase in computation. In \textbf{NH}, in | 
| 896 | 
 contrast, one additional elliptic equation - a three-dimensional one - must | 
 contrast, one additional elliptic equation - a three-dimensional one - must | 
| 900 | 
 hydrostatic limit, is as computationally economic as the \textbf{HPEs}. | 
 hydrostatic limit, is as computationally economic as the \textbf{HPEs}. | 
| 901 | 
  | 
  | 
| 902 | 
 \subsection{Finding the pressure field} | 
 \subsection{Finding the pressure field} | 
| 903 | 
  | 
 \label{sec:finding_the_pressure_field} | 
| 904 | 
  | 
  | 
| 905 | 
 Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the | 
 Unlike the prognostic variables $u$, $v$, $w$, $\theta $ and $S$, the | 
| 906 | 
 pressure field must be obtained diagnostically. We proceed, as before, by | 
 pressure field must be obtained diagnostically. We proceed, as before, by | 
| 915 | 
 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: | 
| 916 | 
  | 
  | 
| 917 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 918 | 
 \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} | 
| 919 | 
 \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr | 
 \right] _{r}^{R_{o}}=\int_{r}^{R_{o}}-bdr | 
| 920 | 
 \end{equation*} | 
 \end{equation*} | 
| 921 | 
 and so | 
 and so | 
| 933 | 
  | 
  | 
| 934 | 
 \subsubsection{Surface pressure} | 
 \subsubsection{Surface pressure} | 
| 935 | 
  | 
  | 
| 936 | 
 The surface pressure equation can be obtained by integrating continuity, (% | 
 The surface pressure equation can be obtained by integrating continuity, | 
| 937 | 
 \ref{eq:continuous})c, vertically from $r=R_{fixed}$ to $r=R_{moving}$ | 
 (\ref{eq:continuity}), vertically from $r=R_{fixed}$ to $r=R_{moving}$ | 
| 938 | 
  | 
  | 
| 939 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 940 | 
 \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} | 
| 941 | 
 }_{h}+\partial _{r}\dot{r}\right) dr=0 | 
 }_{h}+\partial _{r}\dot{r}\right) dr=0 | 
| 942 | 
 \end{equation*} | 
 \end{equation*} | 
| 943 | 
  | 
  | 
| 945 | 
  | 
  | 
| 946 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 947 | 
 \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta | 
 \frac{\partial \eta }{\partial t}+\vec{\mathbf{v}}.\nabla \eta | 
| 948 | 
 +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}}% | 
 +\int_{R_{fixed}}^{R_{moving}}\mathbf{\nabla }_{h}\cdot \vec{\mathbf{v}} | 
| 949 | 
 _{h}dr=0 | 
 _{h}dr=0 | 
| 950 | 
 \end{equation*} | 
 \end{equation*} | 
| 951 | 
 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 $ | 
| 952 | 
 r $. The above can be rearranged to yield, using Leibnitz's theorem: | 
 r $. The above can be rearranged to yield, using Leibnitz's theorem: | 
| 953 | 
  | 
  | 
| 954 | 
 \begin{equation} | 
 \begin{equation} | 
| 955 | 
 \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot | 
 \frac{\partial \eta }{\partial t}+\mathbf{\nabla }_{h}\cdot | 
| 956 | 
 \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source} | 
 \int_{R_{fixed}}^{R_{moving}}\vec{\mathbf{v}}_{h}dr=\text{source} | 
| 957 | 
 \label{eq:free-surface} | 
 \label{eq:free-surface} | 
| 958 | 
 \end{equation}% | 
 \end{equation} | 
| 959 | 
 where we have incorporated a source term. | 
 where we have incorporated a source term. | 
| 960 | 
  | 
  | 
| 961 | 
 Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential | 
 Whether $\phi $ is pressure (ocean model, $p/\rho _{c}$) or geopotential | 
| 962 | 
 (atmospheric model), in (\ref{mtm-split}), the horizontal gradient term can | 
 (atmospheric model), in (\ref{eq:mom-h}), the horizontal gradient term can | 
| 963 | 
 be written  | 
 be written  | 
| 964 | 
 \begin{equation} | 
 \begin{equation} | 
| 965 | 
 \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) | 
| 966 | 
 \label{eq:phi-surf} | 
 \label{eq:phi-surf} | 
| 967 | 
 \end{equation}% | 
 \end{equation} | 
| 968 | 
 where $b_{s}$ is the buoyancy at the surface. | 
 where $b_{s}$ is the buoyancy at the surface. | 
| 969 | 
  | 
  | 
| 970 | 
 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 | 
| 971 | 
 {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 | 
| 972 | 
 elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free | 
 elliptic equation for $\phi _{s}$ as described in Chapter 2. Both `free | 
| 973 | 
 surface' and `rigid lid' approaches are available. | 
 surface' and `rigid lid' approaches are available. | 
| 974 | 
  | 
  | 
| 975 | 
 \subsubsection{Non-hydrostatic pressure} | 
 \subsubsection{Non-hydrostatic pressure} | 
| 976 | 
  | 
  | 
| 977 | 
 Taking the horizontal divergence of (\ref{hor-mtm}) and adding $\frac{% | 
 Taking the horizontal divergence of (\ref{eq:mom-h}) and adding  | 
| 978 | 
 \partial }{\partial r}$ of (\ref{vertmtm}), invoking the continuity equation | 
 $\frac{\partial }{\partial r}$ of (\ref{eq:mom-w}), invoking the continuity equation | 
| 979 | 
 (\ref{incompressible}), we deduce that: | 
 (\ref{eq:continuity}), we deduce that: | 
| 980 | 
  | 
  | 
| 981 | 
 \begin{equation} | 
 \begin{equation} | 
| 982 | 
 \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{ | 
| 983 | 
 \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla .% | 
 \nabla }_{h}^{2}\phi _{s}+\mathbf{\nabla }^{2}\phi _{hyd}\right) =\nabla . | 
| 984 | 
 \vec{\mathbf{F}}  \label{eq:3d-invert} | 
 \vec{\mathbf{F}}  \label{eq:3d-invert} | 
| 985 | 
 \end{equation} | 
 \end{equation} | 
| 986 | 
  | 
  | 
| 1000 | 
 \end{equation} | 
 \end{equation} | 
| 1001 | 
 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 | 
| 1002 | 
 kinematic condition (\ref{nonormalflow}) is also applied to the vertical | 
 kinematic condition (\ref{nonormalflow}) is also applied to the vertical | 
| 1003 | 
 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 $ | 
| 1004 | 
 \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 | 
| 1005 | 
 tangential component of velocity, $v_{T}$, at all solid boundaries, | 
 tangential component of velocity, $v_{T}$, at all solid boundaries, | 
| 1006 | 
 depending on the form chosen for the dissipative terms in the momentum | 
 depending on the form chosen for the dissipative terms in the momentum | 
| 1007 | 
 equations - see below. | 
 equations - see below. | 
| 1008 | 
  | 
  | 
| 1009 | 
 Eq.(\ref{nonormalflow}) implies, making use of (\ref{mtm-split}), that: | 
 Eq.(\ref{nonormalflow}) implies, making use of (\ref{eq:mom-h}), that: | 
| 1010 | 
  | 
  | 
| 1011 | 
 \begin{equation} | 
 \begin{equation} | 
| 1012 | 
 \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}} | 
 \widehat{n}.\nabla \phi _{nh}=\widehat{n}.\vec{\mathbf{F}} | 
| 1017 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1018 | 
 \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 | 
| 1019 | 
 _{s}+\mathbf{\nabla }\phi _{hyd}\right)  | 
 _{s}+\mathbf{\nabla }\phi _{hyd}\right)  | 
| 1020 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1021 | 
 presenting inhomogeneous Neumann boundary conditions to the Elliptic problem | 
 presenting inhomogeneous Neumann boundary conditions to the Elliptic problem | 
| 1022 | 
 (\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 | 
| 1023 | 
 exploit classical 3D potential theory and, by introducing an appropriately | 
 exploit classical 3D potential theory and, by introducing an appropriately | 
| 1024 | 
 chosen $\delta $-function sheet of `source-charge', replace the | 
 chosen $\delta $-function sheet of `source-charge', replace the | 
| 1025 | 
 inhomogeneous boundary condition on pressure by a homogeneous one. The | 
 inhomogeneous boundary condition on pressure by a homogeneous one. The | 
| 1026 | 
 source term $rhs$ in (\ref{eq:3d-invert}) is the divergence of the vector $% | 
 source term $rhs$ in (\ref{eq:3d-invert}) is the divergence of the vector $ | 
| 1027 | 
 \vec{\mathbf{F}}.$ By simultaneously setting $% | 
 \vec{\mathbf{F}}.$ By simultaneously setting $ | 
| 1028 | 
 \begin{array}{l} | 
 \begin{array}{l} | 
| 1029 | 
 \widehat{n}.\vec{\mathbf{F}}% | 
 \widehat{n}.\vec{\mathbf{F}} | 
| 1030 | 
 \end{array}% | 
 \end{array} | 
| 1031 | 
 =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 | 
| 1032 | 
 self-consistent but simpler homogenized Elliptic problem is obtained: | 
 self-consistent but simpler homogenized Elliptic problem is obtained: | 
| 1033 | 
  | 
  | 
| 1034 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1035 | 
 \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad | 
 \nabla ^{2}\phi _{nh}=\nabla .\widetilde{\vec{\mathbf{F}}}\qquad | 
| 1036 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1037 | 
 where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such | 
 where $\widetilde{\vec{\mathbf{F}}}$ is a modified $\vec{\mathbf{F}}$ such | 
| 1038 | 
 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 | 
| 1039 | 
 {eq:inhom-neumann-nh}) the modified boundary condition becomes: | 
 {eq:inhom-neumann-nh}) the modified boundary condition becomes: | 
| 1040 | 
  | 
  | 
| 1041 | 
 \begin{equation} | 
 \begin{equation} | 
| 1046 | 
 converges rapidly because $\phi _{nh}\ $is then only a small correction to | 
 converges rapidly because $\phi _{nh}\ $is then only a small correction to | 
| 1047 | 
 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). | 
| 1048 | 
  | 
  | 
| 1049 | 
 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}) | 
| 1050 | 
 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. | 
| 1051 | 
  | 
  | 
| 1052 | 
 \subsection{Forcing/dissipation} | 
 \subsection{Forcing/dissipation} | 
| 1054 | 
 \subsubsection{Forcing} | 
 \subsubsection{Forcing} | 
| 1055 | 
  | 
  | 
| 1056 | 
 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 | 
| 1057 | 
 `physics packages' described in detail in chapter ??. | 
 `physics packages' and forcing packages. These are described later on. | 
| 1058 | 
  | 
  | 
| 1059 | 
 \subsubsection{Dissipation} | 
 \subsubsection{Dissipation} | 
| 1060 | 
  | 
  | 
| 1064 | 
 biharmonic frictions are commonly used: | 
 biharmonic frictions are commonly used: | 
| 1065 | 
  | 
  | 
| 1066 | 
 \begin{equation} | 
 \begin{equation} | 
| 1067 | 
 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}} | 
| 1068 | 
 +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation} | 
 +A_{4}\nabla _{h}^{4}v  \label{eq:dissipation} | 
| 1069 | 
 \end{equation} | 
 \end{equation} | 
| 1070 | 
 where $A_{h}$ and $A_{v}\ $are (constant) horizontal and vertical viscosity | 
 where $A_{h}$ and $A_{v}\ $are (constant) horizontal and vertical viscosity | 
| 1075 | 
  | 
  | 
| 1076 | 
 The mixing terms for the temperature and salinity equations have a similar | 
 The mixing terms for the temperature and salinity equations have a similar | 
| 1077 | 
 form to that of momentum except that the diffusion tensor can be | 
 form to that of momentum except that the diffusion tensor can be | 
| 1078 | 
 non-diagonal and have varying coefficients. $\qquad $% | 
 non-diagonal and have varying coefficients. $\qquad $ | 
| 1079 | 
 \begin{equation} | 
 \begin{equation} | 
| 1080 | 
 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 | 
| 1081 | 
 _{h}^{4}(T,S)  \label{eq:diffusion} | 
 _{h}^{4}(T,S)  \label{eq:diffusion} | 
| 1082 | 
 \end{equation} | 
 \end{equation} | 
| 1083 | 
 where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $% | 
 where $\underline{\underline{K}}\ $is the diffusion tensor and the $K_{4}\ $ | 
| 1084 | 
 horizontal coefficient for biharmonic diffusion. In the simplest case where | 
 horizontal coefficient for biharmonic diffusion. In the simplest case where | 
| 1085 | 
 the subgrid-scale fluxes of heat and salt are parameterized with constant | 
 the subgrid-scale fluxes of heat and salt are parameterized with constant | 
| 1086 | 
 horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$, | 
 horizontal and vertical diffusion coefficients, $\underline{\underline{K}}$, | 
| 1091 | 
 \begin{array}{ccc} | 
 \begin{array}{ccc} | 
| 1092 | 
 K_{h} & 0 & 0 \\  | 
 K_{h} & 0 & 0 \\  | 
| 1093 | 
 0 & K_{h} & 0 \\  | 
 0 & K_{h} & 0 \\  | 
| 1094 | 
 0 & 0 & K_{v}% | 
 0 & 0 & K_{v} | 
| 1095 | 
 \end{array} | 
 \end{array} | 
| 1096 | 
 \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor} | 
 \right) \qquad \qquad \qquad  \label{eq:diagonal-diffusion-tensor} | 
| 1097 | 
 \end{equation} | 
 \end{equation} | 
| 1101 | 
  | 
  | 
| 1102 | 
 \subsection{Vector invariant form} | 
 \subsection{Vector invariant form} | 
| 1103 | 
  | 
  | 
| 1104 | 
 For some purposes it is advantageous to write momentum advection in eq(\ref% | 
 For some purposes it is advantageous to write momentum advection in | 
| 1105 | 
 {hor-mtm}) and (\ref{vertmtm}) in the (so-called) `vector invariant' form: | 
 eq(\ref {eq:horizontal_mtm}) and (\ref{eq:vertical_mtm}) in the | 
| 1106 | 
  | 
 (so-called) `vector invariant' form: | 
| 1107 | 
  | 
  | 
| 1108 | 
 \begin{equation} | 
 \begin{equation} | 
| 1109 | 
 \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} | 
| 1110 | 
 +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla % | 
 +\left( \nabla \times \vec{\mathbf{v}}\right) \times \vec{\mathbf{v}}+\nabla  | 
| 1111 | 
 \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right] | 
 \left[ \frac{1}{2}(\vec{\mathbf{v}}\cdot \vec{\mathbf{v}})\right] | 
| 1112 | 
 \label{eq:vi-identity} | 
 \label{eq:vi-identity} | 
| 1113 | 
 \end{equation}% | 
 \end{equation} | 
| 1114 | 
 This permits alternative numerical treatments of the non-linear terms based | 
 This permits alternative numerical treatments of the non-linear terms based | 
| 1115 | 
 on their representation as a vorticity flux. Because gradients of coordinate | 
 on their representation as a vorticity flux. Because gradients of coordinate | 
| 1116 | 
 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 | 
| 1117 | 
 representation of the metric terms in (\ref{eq:gu-speherical}), (\ref% | 
 representation of the metric terms in (\ref{eq:gu-speherical}), (\ref | 
| 1118 | 
 {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information | 
 {eq:gv-spherical}) and (\ref{eq:gw-spherical}), can be avoided: information | 
| 1119 | 
 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 | 
| 1120 | 
 to discretize the model. | 
 to discretize the model. | 
| 1121 | 
  | 
  | 
| 1122 | 
 \subsection{Adjoint} | 
 \subsection{Adjoint} | 
| 1123 | 
  | 
  | 
| 1124 | 
 Tangent linear and adjoint counterparts of the forward model and described | 
 Tangent linear and adjoint counterparts of the forward model are described | 
| 1125 | 
 in Chapter 5. | 
 in Chapter 5. | 
| 1126 | 
  | 
  | 
| 1127 | 
 % $Header$ | 
 % $Header$ | 
| 1136 | 
  | 
  | 
| 1137 | 
 The hydrostatic primitive equations (HPEs) in p-coordinates are:  | 
 The hydrostatic primitive equations (HPEs) in p-coordinates are:  | 
| 1138 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1139 | 
 \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}} | 
| 1140 | 
 _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}} | 
 _{h}+\mathbf{\nabla }_{p}\phi &=&\vec{\mathbf{\mathcal{F}}} | 
| 1141 | 
 \label{eq:atmos-mom} \\ | 
 \label{eq:atmos-mom} \\ | 
| 1142 | 
 \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\ | 
 \frac{\partial \phi }{\partial p}+\alpha &=&0  \label{eq-p-hydro-start} \\ | 
| 1143 | 
 \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{% | 
 \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{ | 
| 1144 | 
 \partial p} &=&0  \label{eq:atmos-cont} \\ | 
 \partial p} &=&0  \label{eq:atmos-cont} \\ | 
| 1145 | 
 p\alpha &=&RT  \label{eq:atmos-eos} \\ | 
 p\alpha &=&RT  \label{eq:atmos-eos} \\ | 
| 1146 | 
 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} | 
| 1147 | 
 \end{eqnarray}% | 
 \end{eqnarray} | 
| 1148 | 
 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 | 
| 1149 | 
 surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  | 
 surfaces) component of velocity,$\frac{D}{Dt}=\vec{\mathbf{v}}_{h}\cdot  | 
| 1150 | 
 \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total | 
 \mathbf{\nabla }_{p}+\omega \frac{\partial }{\partial p}$ is the total | 
| 1151 | 
 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 | 
| 1152 | 
 the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp% | 
 the geopotential, $\alpha =1/\rho $ is the specific volume, $\omega =\frac{Dp | 
| 1153 | 
 }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref% | 
 }{Dt}$ is the vertical velocity in the $p-$coordinate. Equation(\ref | 
| 1154 | 
 {eq:atmos-heat}) is the first law of thermodynamics where internal energy $% | 
 {eq:atmos-heat}) is the first law of thermodynamics where internal energy $ | 
| 1155 | 
 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 $ | 
| 1156 | 
 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. | 
| 1157 | 
  | 
  | 
| 1158 | 
 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  | 
| 1160 | 
 Differentiating (\ref{eq:atmos-eos}) we get:  | 
 Differentiating (\ref{eq:atmos-eos}) we get:  | 
| 1161 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1162 | 
 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} | 
| 1163 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1164 | 
 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 $ | 
| 1165 | 
 c_{p}=c_{v}+R$, gives:  | 
 c_{p}=c_{v}+R$, gives:  | 
| 1166 | 
 \begin{equation} | 
 \begin{equation} | 
| 1167 | 
 c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q} | 
 c_{p}\frac{DT}{Dt}-\alpha \frac{Dp}{Dt}=\mathcal{Q} | 
| 1168 | 
 \label{eq-p-heat-interim} | 
 \label{eq-p-heat-interim} | 
| 1169 | 
 \end{equation}% | 
 \end{equation} | 
| 1170 | 
 Potential temperature is defined:  | 
 Potential temperature is defined:  | 
| 1171 | 
 \begin{equation} | 
 \begin{equation} | 
| 1172 | 
 \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp} | 
 \theta =T(\frac{p_{c}}{p})^{\kappa }  \label{eq:potential-temp} | 
| 1173 | 
 \end{equation}% | 
 \end{equation} | 
| 1174 | 
 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 | 
| 1175 | 
 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:  | 
| 1176 | 
 \begin{equation} | 
 \begin{equation} | 
| 1177 | 
 \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner} | 
 \Pi (p)=c_{p}(\frac{p}{p_{c}})^{\kappa }  \label{Exner} | 
| 1178 | 
 \end{equation}% | 
 \end{equation} | 
| 1179 | 
 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 | 
| 1180 | 
 the Exner function:  | 
 the Exner function:  | 
| 1181 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1182 | 
 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  | 
| 1183 | 
 }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{% | 
 }{p}\;\;;\;\;\alpha =\frac{\kappa \Pi \theta }{p}=\frac{\partial \ \Pi }{ | 
| 1184 | 
 \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p}% | 
 \partial p}\theta \;\;;\;\;\frac{D\Pi }{Dt}=\frac{\partial \Pi }{\partial p} | 
| 1185 | 
 \frac{Dp}{Dt} | 
 \frac{Dp}{Dt} | 
| 1186 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1187 | 
 where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy. | 
 where $b=\frac{\partial \ \Pi }{\partial p}\theta $ is the buoyancy. | 
| 1188 | 
  | 
  | 
| 1189 | 
 The heat equation is obtained by noting that  | 
 The heat equation is obtained by noting that  | 
| 1198 | 
 \end{equation} | 
 \end{equation} | 
| 1199 | 
 which is in conservative form. | 
 which is in conservative form. | 
| 1200 | 
  | 
  | 
| 1201 | 
 For convenience in the model we prefer to step forward (\ref% | 
 For convenience in the model we prefer to step forward (\ref | 
| 1202 | 
 {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}). | 
 {eq:potential-temperature-equation}) rather than (\ref{eq:atmos-heat}). | 
| 1203 | 
  | 
  | 
| 1204 | 
 \subsubsection{Boundary conditions} | 
 \subsubsection{Boundary conditions} | 
| 1214 | 
 surface ($\phi $ is imposed and $\omega \neq 0$). | 
 surface ($\phi $ is imposed and $\omega \neq 0$). | 
| 1215 | 
  | 
  | 
| 1216 | 
 \subsubsection{Splitting the geo-potential} | 
 \subsubsection{Splitting the geo-potential} | 
| 1217 | 
  | 
 \label{sec:hpe-p-geo-potential-split} | 
| 1218 | 
  | 
  | 
| 1219 | 
 For the purposes of initialization and reducing round-off errors, the model | 
 For the purposes of initialization and reducing round-off errors, the model | 
| 1220 | 
 deals with perturbations from reference (or ``standard'') profiles. For | 
 deals with perturbations from reference (or ``standard'') profiles. For | 
| 1243 | 
  | 
  | 
| 1244 | 
 The final form of the HPE's in p coordinates is then:  | 
 The final form of the HPE's in p coordinates is then:  | 
| 1245 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1246 | 
 \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}} | 
| 1247 | 
 _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}} \\ | 
 _{h}+\mathbf{\nabla }_{p}\phi ^{\prime } &=&\vec{\mathbf{\mathcal{F}}}  | 
| 1248 | 
  | 
 \label{eq:atmos-prime} \\ | 
| 1249 | 
 \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\ | 
 \frac{\partial \phi ^{\prime }}{\partial p}+\alpha ^{\prime } &=&0 \\ | 
| 1250 | 
 \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{% | 
 \mathbf{\nabla }_{p}\cdot \vec{\mathbf{v}}_{h}+\frac{\partial \omega }{ | 
| 1251 | 
 \partial p} &=&0 \\ | 
 \partial p} &=&0 \\ | 
| 1252 | 
 \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\ | 
 \frac{\partial \Pi }{\partial p}\theta ^{\prime } &=&\alpha ^{\prime } \\ | 
| 1253 | 
 \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  \label{eq:atmos-prime} | 
 \frac{D\theta }{Dt} &=&\frac{\mathcal{Q}}{\Pi }  | 
| 1254 | 
 \end{eqnarray} | 
 \end{eqnarray} | 
| 1255 | 
  | 
  | 
| 1256 | 
 % $Header$ | 
 % $Header$ | 
| 1264 | 
 HPE's for the ocean written in z-coordinates are obtained. The | 
 HPE's for the ocean written in z-coordinates are obtained. The | 
| 1265 | 
 non-Boussinesq equations for oceanic motion are:  | 
 non-Boussinesq equations for oceanic motion are:  | 
| 1266 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1267 | 
 \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}} | 
| 1268 | 
 _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\ | 
 _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} \\ | 
| 1269 | 
 \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} | 
| 1270 | 
 &=&\epsilon _{nh}\mathcal{F}_{w} \\ | 
 &=&\epsilon _{nh}\mathcal{F}_{w} \\ | 
| 1271 | 
 \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}} | 
| 1272 | 
 _{h}+\frac{\partial w}{\partial z} &=&0 \\ | 
 _{h}+\frac{\partial w}{\partial z} &=&0 \label{eq-zns-cont}\\ | 
| 1273 | 
 \rho &=&\rho (\theta ,S,p) \\ | 
 \rho &=&\rho (\theta ,S,p) \label{eq-zns-eos}\\ | 
| 1274 | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \\ | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta } \label{eq-zns-heat}\\ | 
| 1275 | 
 \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:non-boussinesq} | 
 \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zns-salt} | 
| 1276 | 
 \end{eqnarray}% | 
 \label{eq:non-boussinesq} | 
| 1277 | 
  | 
 \end{eqnarray} | 
| 1278 | 
 These equations permit acoustics modes, inertia-gravity waves, | 
 These equations permit acoustics modes, inertia-gravity waves, | 
| 1279 | 
 non-hydrostatic motions, a geostrophic (Rossby) mode and a thermo-haline | 
 non-hydrostatic motions, a geostrophic (Rossby) mode and a thermohaline | 
| 1280 | 
 mode. As written, they cannot be integrated forward consistently - if we | 
 mode. As written, they cannot be integrated forward consistently - if we | 
| 1281 | 
 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 | 
| 1282 | 
 consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref% | 
 consistent with that obtained by stepping (\ref{eq-zns-heat}) and (\ref | 
| 1283 | 
 {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 | 
| 1284 | 
 therefore necessary to manipulate the system as follows. Differentiating the | 
 therefore necessary to manipulate the system as follows. Differentiating the | 
| 1285 | 
 EOS (equation of state) gives: | 
 EOS (equation of state) gives: | 
| 1291 | 
 _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexpansion} | 
 _{\theta ,S}\frac{Dp}{Dt}  \label{EOSexpansion} | 
| 1292 | 
 \end{equation} | 
 \end{equation} | 
| 1293 | 
  | 
  | 
| 1294 | 
 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 | 
| 1295 | 
 reciprocal of the sound speed ($c_{s}$) squared. Substituting into \ref% | 
 the reciprocal of the sound speed ($c_{s}$) squared. Substituting into | 
| 1296 | 
 {eq-zns-cont} gives:  | 
 \ref{eq-zns-cont} gives: | 
| 1297 | 
 \begin{equation} | 
 \begin{equation} | 
| 1298 | 
 \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{ | 
| 1299 | 
 v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure} | 
 v}}+\partial _{z}w\approx 0  \label{eq-zns-pressure} | 
| 1300 | 
 \end{equation} | 
 \end{equation} | 
| 1301 | 
 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 | 
| 1303 | 
 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 | 
| 1304 | 
 can be explicitly integrated forward:  | 
 can be explicitly integrated forward:  | 
| 1305 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1306 | 
 \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}} | 
| 1307 | 
 _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} | 
 _{h}+\frac{1}{\rho }\mathbf{\nabla }_{z}p &=&\vec{\mathbf{\mathcal{F}}} | 
| 1308 | 
 \label{eq-cns-hmom} \\ | 
 \label{eq-cns-hmom} \\ | 
| 1309 | 
 \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} | 
| 1310 | 
 &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\ | 
 &=&\epsilon _{nh}\mathcal{F}_{w}  \label{eq-cns-hydro} \\ | 
| 1311 | 
 \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{ | 
| 1312 | 
 v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\ | 
 v}}_{h}+\frac{\partial w}{\partial z} &=&0  \label{eq-cns-cont} \\ | 
| 1313 | 
 \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\ | 
 \rho &=&\rho (\theta ,S,p)  \label{eq-cns-eos} \\ | 
| 1314 | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\ | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-cns-heat} \\ | 
| 1322 | 
 `Boussinesq assumption'. The only term that then retains the full variation | 
 `Boussinesq assumption'. The only term that then retains the full variation | 
| 1323 | 
 in $\rho $ is the gravitational acceleration:  | 
 in $\rho $ is the gravitational acceleration:  | 
| 1324 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1325 | 
 \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}} | 
| 1326 | 
 _{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}}} | 
| 1327 | 
 \label{eq-zcb-hmom} \\ | 
 \label{eq-zcb-hmom} \\ | 
| 1328 | 
 \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}} | 
| 1329 | 
 \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
 \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
| 1330 | 
 \label{eq-zcb-hydro} \\ | 
 \label{eq-zcb-hydro} \\ | 
| 1331 | 
 \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{ | 
| 1332 | 
 \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} \\ | 
| 1333 | 
 \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\ | 
 \rho &=&\rho (\theta ,S,p)  \label{eq-zcb-eos} \\ | 
| 1334 | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\ | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zcb-heat} \\ | 
| 1335 | 
 \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt} | 
 \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq-zcb-salt} | 
| 1336 | 
 \end{eqnarray} | 
 \end{eqnarray} | 
| 1337 | 
 These equations still retain acoustic modes. But, because the | 
 These equations still retain acoustic modes. But, because the | 
| 1338 | 
 ``compressible'' terms are linearized, the pressure equation \ref% | 
 ``compressible'' terms are linearized, the pressure equation \ref | 
| 1339 | 
 {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent | 
 {eq-zcb-cont} can be integrated implicitly with ease (the time-dependent | 
| 1340 | 
 term appears as a Helmholtz term in the non-hydrostatic pressure equation). | 
 term appears as a Helmholtz term in the non-hydrostatic pressure equation). | 
| 1341 | 
 These are the \emph{truly} compressible Boussinesq equations. Note that the | 
 These are the \emph{truly} compressible Boussinesq equations. Note that the | 
| 1342 | 
 EOS must have the same pressure dependency as the linearized pressure term, | 
 EOS must have the same pressure dependency as the linearized pressure term, | 
| 1343 | 
 ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{% | 
 ie. $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}=\frac{1}{ | 
| 1344 | 
 c_{s}^{2}}$, for consistency. | 
 c_{s}^{2}}$, for consistency. | 
| 1345 | 
  | 
  | 
| 1346 | 
 \subsubsection{`Anelastic' z-coordinate equations} | 
 \subsubsection{`Anelastic' z-coordinate equations} | 
| 1347 | 
  | 
  | 
| 1348 | 
 The anelastic approximation filters the acoustic mode by removing the | 
 The anelastic approximation filters the acoustic mode by removing the | 
| 1349 | 
 time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont}% | 
 time-dependency in the continuity (now pressure-) equation (\ref{eq-zcb-cont} | 
| 1350 | 
 ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o}% | 
 ). This could be done simply by noting that $\frac{Dp}{Dt}\approx -g\rho _{o} | 
| 1351 | 
 \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between | 
 \frac{Dz}{Dt}=-g\rho _{o}w$, but this leads to an inconsistency between | 
| 1352 | 
 continuity and EOS. A better solution is to change the dependency on | 
 continuity and EOS. A better solution is to change the dependency on | 
| 1353 | 
 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 | 
| 1358 | 
 Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from | 
 Remembering that the term $\frac{Dp}{Dt}$ in continuity comes from | 
| 1359 | 
 differentiating the EOS, the continuity equation then becomes:  | 
 differentiating the EOS, the continuity equation then becomes:  | 
| 1360 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1361 | 
 \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{ | 
| 1362 | 
 Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+% | 
 Dp^{\prime }}{Dt}\right) +\mathbf{\nabla }_{z}\cdot \vec{\mathbf{v}}_{h}+ | 
| 1363 | 
 \frac{\partial w}{\partial z}=0 | 
 \frac{\partial w}{\partial z}=0 | 
| 1364 | 
 \end{equation*} | 
 \end{equation*} | 
| 1365 | 
 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 | 
| 1366 | 
 those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt},% | 
 those of acoustic modes, then $\frac{Dp^{\prime }}{Dt}<<(\frac{Dp_{o}}{Dt}, | 
| 1367 | 
 \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  | 
 \mathbf{\nabla }\cdot \vec{\mathbf{v}}_{h})$ in the continuity equations and  | 
| 1368 | 
 $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{% | 
 $\left. \frac{\partial \rho }{\partial p}\right| _{\theta ,S}\frac{ | 
| 1369 | 
 Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta | 
 Dp^{\prime }}{Dt}<<\left. \frac{\partial \rho }{\partial p}\right| _{\theta | 
| 1370 | 
 ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon | 
 ,S}\frac{Dp_{o}}{Dt}$ in the EOS (\ref{EOSexpansion}). Thus we set $\epsilon | 
| 1371 | 
 _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation | 
 _{s}=0$, removing the dependency on $p^{\prime }$ in the continuity equation | 
| 1372 | 
 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 | 
| 1373 | 
 anelastic continuity equation:  | 
 anelastic continuity equation:  | 
| 1374 | 
 \begin{equation} | 
 \begin{equation} | 
| 1375 | 
 \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}- | 
| 1376 | 
 \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1} | 
 \frac{g}{c_{s}^{2}}w=0  \label{eq-za-cont1} | 
| 1377 | 
 \end{equation} | 
 \end{equation} | 
| 1378 | 
 A slightly different route leads to the quasi-Boussinesq continuity equation | 
 A slightly different route leads to the quasi-Boussinesq continuity equation | 
| 1379 | 
 where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+% | 
 where we use the scaling $\frac{\partial \rho ^{\prime }}{\partial t}+ | 
| 1380 | 
 \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla }% | 
 \mathbf{\nabla }_{3}\cdot \rho ^{\prime }\vec{\mathbf{v}}<<\mathbf{\nabla } | 
| 1381 | 
 _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  | 
 _{3}\cdot \rho _{o}\vec{\mathbf{v}}$ yielding:  | 
| 1382 | 
 \begin{equation} | 
 \begin{equation} | 
| 1383 | 
 \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{ | 
| 1384 | 
 \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} | 
| 1385 | 
 \end{equation} | 
 \end{equation} | 
| 1386 | 
 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 | 
| 1389 | 
 \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}} | 
| 1390 | 
 \end{equation} | 
 \end{equation} | 
| 1391 | 
 Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$ | 
 Again, note that if $\rho _{o}$ is evaluated from prescribed $\theta _{o}$ | 
| 1392 | 
 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 $\frac{ | 
| 1393 | 
 g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The | 
 g}{c_{s}^{2}}$ in continuity should be referred to those same profiles. The | 
| 1394 | 
 full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are | 
 full set of `quasi-Boussinesq' or `anelastic' equations for the ocean are | 
| 1395 | 
 then:  | 
 then:  | 
| 1396 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1397 | 
 \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}} | 
| 1398 | 
 _{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}}} | 
| 1399 | 
 \label{eq-zab-hmom} \\ | 
 \label{eq-zab-hmom} \\ | 
| 1400 | 
 \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}} | 
| 1401 | 
 \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
 \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
| 1402 | 
 \label{eq-zab-hydro} \\ | 
 \label{eq-zab-hydro} \\ | 
| 1403 | 
 \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{ | 
| 1404 | 
 \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} \\ | 
| 1405 | 
 \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\ | 
 \rho &=&\rho (\theta ,S,p_{o}(z))  \label{eq-zab-eos} \\ | 
| 1406 | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\ | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq-zab-heat} \\ | 
| 1413 | 
 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 | 
| 1414 | 
 yield the ``truly'' incompressible Boussinesq equations:  | 
 yield the ``truly'' incompressible Boussinesq equations:  | 
| 1415 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1416 | 
 \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}} | 
| 1417 | 
 _{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}}} | 
| 1418 | 
 \label{eq-ztb-hmom} \\ | 
 \label{eq-ztb-hmom} \\ | 
| 1419 | 
 \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}} | 
| 1420 | 
 \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
 \frac{\partial p}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
| 1421 | 
 \label{eq-ztb-hydro} \\ | 
 \label{eq-ztb-hydro} \\ | 
| 1422 | 
 \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} | 
| 1435 | 
 density thus:  | 
 density thus:  | 
| 1436 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1437 | 
 \rho =\rho _{o}+\rho ^{\prime } | 
 \rho =\rho _{o}+\rho ^{\prime } | 
| 1438 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1439 | 
 We then assert that variations with depth of $\rho _{o}$ are unimportant | 
 We then assert that variations with depth of $\rho _{o}$ are unimportant | 
| 1440 | 
 while the compressible effects in $\rho ^{\prime }$ are:  | 
 while the compressible effects in $\rho ^{\prime }$ are:  | 
| 1441 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1442 | 
 \rho _{o}=\rho _{c} | 
 \rho _{o}=\rho _{c} | 
| 1443 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1444 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1445 | 
 \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o} | 
 \rho ^{\prime }=\rho (\theta ,S,p_{o}(z))-\rho _{o} | 
| 1446 | 
 \end{equation*}% | 
 \end{equation*} | 
| 1447 | 
 This then yields what we can call the semi-compressible Boussinesq | 
 This then yields what we can call the semi-compressible Boussinesq | 
| 1448 | 
 equations:  | 
 equations:  | 
| 1449 | 
 \begin{eqnarray} | 
 \begin{eqnarray} | 
| 1450 | 
 \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}} | 
| 1451 | 
 _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{% | 
 _{h}+\frac{1}{\rho _{c}}\mathbf{\nabla }_{z}p^{\prime } &=&\vec{\mathbf{ | 
| 1452 | 
 \mathcal{F}}}  \label{eq:ocean-mom} \\ | 
 \mathcal{F}}}  \label{eq:ocean-mom} \\ | 
| 1453 | 
 \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 | 
| 1454 | 
 _{c}}\frac{\partial p^{\prime }}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
 _{c}}\frac{\partial p^{\prime }}{\partial z} &=&\epsilon _{nh}\mathcal{F}_{w} | 
| 1459 | 
 \\ | 
 \\ | 
| 1460 | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\ | 
 \frac{D\theta }{Dt} &=&\mathcal{Q}_{\theta }  \label{eq:ocean-theta} \\ | 
| 1461 | 
 \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt} | 
 \frac{DS}{Dt} &=&\mathcal{Q}_{s}  \label{eq:ocean-salt} | 
| 1462 | 
 \end{eqnarray}% | 
 \end{eqnarray} | 
| 1463 | 
 Note that the hydrostatic pressure of the resting fluid, including that | 
 Note that the hydrostatic pressure of the resting fluid, including that | 
| 1464 | 
 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 | 
| 1465 | 
 dynamics. | 
 dynamics. | 
| 1483 | 
 and vertical direction respectively, are given by (see Fig.2) : | 
 and vertical direction respectively, are given by (see Fig.2) : | 
| 1484 | 
  | 
  | 
| 1485 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1486 | 
 u=r\cos \phi \frac{D\lambda }{Dt} | 
 u=r\cos \varphi \frac{D\lambda }{Dt} | 
| 1487 | 
 \end{equation*} | 
 \end{equation*} | 
| 1488 | 
  | 
  | 
| 1489 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1490 | 
 v=r\frac{D\phi }{Dt}\qquad | 
 v=r\frac{D\varphi }{Dt}\qquad | 
| 1491 | 
 \end{equation*} | 
 \end{equation*} | 
| 1492 | 
 $\qquad \qquad \qquad \qquad $ | 
 $\qquad \qquad \qquad \qquad $ | 
| 1493 | 
  | 
  | 
| 1495 | 
 \dot{r}=\frac{Dr}{Dt} | 
 \dot{r}=\frac{Dr}{Dt} | 
| 1496 | 
 \end{equation*} | 
 \end{equation*} | 
| 1497 | 
  | 
  | 
| 1498 | 
 Here $\phi $ is the latitude, $\lambda $ the longitude, $r$ the radial | 
 Here $\varphi $ is the latitude, $\lambda $ the longitude, $r$ the radial | 
| 1499 | 
 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 | 
| 1500 | 
 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. | 
| 1501 | 
  | 
  | 
| 1503 | 
 spherical coordinates: | 
 spherical coordinates: | 
| 1504 | 
  | 
  | 
| 1505 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1506 | 
 \nabla \equiv \left( \frac{1}{r\cos \phi }\frac{\partial }{\partial \lambda }% | 
 \nabla \equiv \left( \frac{1}{r\cos \varphi }\frac{\partial }{\partial \lambda } | 
| 1507 | 
 ,\frac{1}{r}\frac{\partial }{\partial \phi },\frac{\partial }{\partial r}% | 
 ,\frac{1}{r}\frac{\partial }{\partial \varphi },\frac{\partial }{\partial r} | 
| 1508 | 
 \right) | 
 \right) | 
| 1509 | 
 \end{equation*} | 
 \end{equation*} | 
| 1510 | 
  | 
  | 
| 1511 | 
 \begin{equation*} | 
 \begin{equation*} | 
| 1512 | 
 \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 | 
| 1513 | 
 \lambda }+\frac{\partial }{\partial \phi }\left( v\cos \phi \right) \right\} | 
 \lambda }+\frac{\partial }{\partial \varphi }\left( v\cos \varphi \right) \right\} | 
| 1514 | 
 +\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} | 
| 1515 | 
 \end{equation*} | 
 \end{equation*} | 
| 1516 | 
  | 
  | 
| 1517 | 
 %%%% \end{document} | 
 %tci%\end{document} |