Changeset 9392 for branches/2017/dev_merge_2017/DOC/tex_sub/chap_LBC.tex
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- 2018-03-09T16:57:00+01:00 (6 years ago)
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branches/2017/dev_merge_2017/DOC/tex_sub/chap_LBC.tex
r9389 r9392 17 17 % Boundary Condition at the Coast 18 18 % ================================================================ 19 \section{Boundary Condition at the Coast (\protect\np{rn \_shlat})}19 \section{Boundary Condition at the Coast (\protect\np{rn_shlat})} 20 20 \label{LBC_coast} 21 21 %--------------------------------------------nam_lbc------------------------------------------------------- … … 72 72 condition influences the relative vorticity and momentum diffusive trends, and is 73 73 required in order to compute the vorticity at the coast. Four different types of 74 lateral boundary condition are available, controlled by the value of the \np{rn \_shlat}74 lateral boundary condition are available, controlled by the value of the \np{rn_shlat} 75 75 namelist parameter. (The value of the mask$_{f}$ array along the coastline is set 76 76 equal to this parameter.) These are: … … 88 88 \begin{description} 89 89 90 \item[free-slip boundary condition (\ np{rn\_shlat}=0): ] the tangential velocity at the90 \item[free-slip boundary condition (\forcode{rn_shlat = 0}): ] the tangential velocity at the 91 91 coastline is equal to the offshore velocity, $i.e.$ the normal derivative of the 92 92 tangential velocity is zero at the coast, so the vorticity: mask$_{f}$ array is set 93 93 to zero inside the land and just at the coast (Fig.~\ref{Fig_LBC_shlat}-a). 94 94 95 \item[no-slip boundary condition (\ np{rn\_shlat}=2): ] the tangential velocity vanishes95 \item[no-slip boundary condition (\forcode{rn_shlat = 2}): ] the tangential velocity vanishes 96 96 at the coastline. Assuming that the tangential velocity decreases linearly from 97 97 the closest ocean velocity grid point to the coastline, the normal derivative is … … 112 112 \end{equation} 113 113 114 \item["partial" free-slip boundary condition (0$<$\np{rn \_shlat}$<$2): ] the tangential114 \item["partial" free-slip boundary condition (0$<$\np{rn_shlat}$<$2): ] the tangential 115 115 velocity at the coastline is smaller than the offshore velocity, $i.e.$ there is a lateral 116 116 friction but not strong enough to make the tangential velocity at the coast vanish … … 118 118 strictly inbetween $0$ and $2$. 119 119 120 \item["strong" no-slip boundary condition (2$<$\np{rn \_shlat}): ] the viscous boundary120 \item["strong" no-slip boundary condition (2$<$\np{rn_shlat}): ] the viscous boundary 121 121 layer is assumed to be smaller than half the grid size (Fig.~\ref{Fig_LBC_shlat}-d). 122 122 The friction is thus larger than in the no-slip case. … … 331 331 the model output files is undefined. Note that this is a problem for the meshmask file 332 332 which requires to be defined over the whole domain. Therefore, user should not eliminate 333 land processors when creating a meshmask file ($i.e.$ when setting a non-zero value to \np{nn \_msh}).333 land processors when creating a meshmask file ($i.e.$ when setting a non-zero value to \np{nn_msh}). 334 334 335 335 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> … … 387 387 \label{BDY_namelist} 388 388 389 The BDY module is activated by setting \np{ln \_bdy} to true.389 The BDY module is activated by setting \np{ln_bdy} to true. 390 390 It is possible to define more than one boundary ``set'' and apply 391 391 different boundary conditions to each set. The number of boundary 392 sets is defined by \np{nb \_bdy}. Each boundary set may be defined392 sets is defined by \np{nb_bdy}. Each boundary set may be defined 393 393 as a set of straight line segments in a namelist 394 (\np{ln \_coords\_file}=.false.) or read in from a file395 (\np{ln \_coords\_file}=.true.). If the set is defined in a namelist,394 (\np{ln_coords_file}=.false.) or read in from a file 395 (\np{ln_coords_file}=.true.). If the set is defined in a namelist, 396 396 then the namelists nambdy\_index must be included separately, one for 397 397 each set. If the set is defined by a file, then a 398 `` coordinates.bdy.nc'' file must be provided. The coordinates.bdy file399 is analagous to the usual NEMO `` coordinates.nc'' file. In the example398 ``\ifile{coordinates.bdy}'' file must be provided. The coordinates.bdy file 399 is analagous to the usual NEMO ``\ifile{coordinates}'' file. In the example 400 400 above, there are two boundary sets, the first of which is defined via 401 401 a file and the second is defined in a namelist. For more details of … … 410 410 (``tra''). For each set of variables there is a choice of algorithm 411 411 and a choice for the data, eg. for the active tracers the algorithm is 412 set by \np{nn \_tra} and the choice of data is set by413 \np{nn \_tra\_dta}.412 set by \np{nn_tra} and the choice of data is set by 413 \np{nn_tra_dta}. 414 414 415 415 The choice of algorithm is currently as follows: … … 429 429 430 430 The main choice for the boundary data is 431 to use initial conditions as boundary data (\ np{nn\_tra\_dta}=0) or to432 use external data from a file (\ np{nn\_tra\_dta}=1). For the431 to use initial conditions as boundary data (\forcode{nn_tra_dta = 0}) or to 432 use external data from a file (\forcode{nn_tra_dta = 1}). For the 433 433 barotropic solution there is also the option to use tidal 434 434 harmonic forcing either by itself or in addition to other external … … 492 492 \end{equation} 493 493 The width of the FRS zone is specified in the namelist as 494 \np{nn \_rimwidth}. This is typically set to a value between 8 and 10.494 \np{nn_rimwidth}. This is typically set to a value between 8 and 10. 495 495 496 496 %---------------------------------------------- … … 534 534 535 535 The boundary geometry for each set may be defined in a namelist 536 nambdy\_index or by reading in a `` coordinates.bdy.nc'' file. The536 nambdy\_index or by reading in a ``\ifile{coordinates.bdy}'' file. The 537 537 nambdy\_index namelist defines a series of straight-line segments for 538 538 north, east, south and west boundaries. For the northern boundary, … … 546 546 547 547 The boundary geometry may also be defined from a 548 `` coordinates.bdy.nc'' file. Figure \ref{Fig_LBC_nc_header}548 ``\ifile{coordinates.bdy}'' file. Figure \ref{Fig_LBC_nc_header} 549 549 gives an example of the header information from such a file. The file 550 550 should contain the index arrays for each of the $T$, $U$ and $V$ … … 561 561 shelf break, then the areas of ocean outside of this boundary will 562 562 need to be masked out. This can be done by reading a mask file defined 563 as \np{cn \_mask\_file} in the nam\_bdy namelist. Only one mask file is563 as \np{cn_mask_file} in the nam\_bdy namelist. Only one mask file is 564 564 used even if multiple boundary sets are defined. 565 565 … … 609 609 \includegraphics[width=1.0\textwidth]{Fig_LBC_nc_header} 610 610 \caption { \protect\label{Fig_LBC_nc_header} 611 Example of the header for a coordinates.bdy.ncfile}611 Example of the header for a \ifile{coordinates.bdy} file} 612 612 \end{center} \end{figure} 613 613 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> … … 618 618 619 619 There is an option to force the total volume in the regional model to be constant, 620 similar to the option in the OBC module. This is controlled by the \np{nn \_volctl}621 parameter in the namelist. A value of \np{nn \_volctl}~=~0 indicates that this option is not used.622 If \np{nn \_volctl}~=~1 then a correction is applied to the normal velocities620 similar to the option in the OBC module. This is controlled by the \np{nn_volctl} 621 parameter in the namelist. A value of \np{nn_volctl}~=~0 indicates that this option is not used. 622 If \np{nn_volctl}~=~1 then a correction is applied to the normal velocities 623 623 around the boundary at each timestep to ensure that the integrated volume flow 624 through the boundary is zero. If \np{nn \_volctl}~=~2 then the calculation of624 through the boundary is zero. If \np{nn_volctl}~=~2 then the calculation of 625 625 the volume change on the timestep includes the change due to the freshwater 626 626 flux across the surface and the correction velocity corrects for this as well.
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