Changeset 11445


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Timestamp:
2019-08-19T09:18:20+02:00 (8 months ago)
Author:
sciliberti
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#2216 revision of LBC chapter: main ones in bdy description and geometry

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1 edited

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  • NEMO/trunk/doc/latex/NEMO/subfiles/chap_LBC.tex

    r11435 r11445  
    151151\end{description} 
    152152 
    153 Note that when the bottom topography is entirely represented by the $s$-coor-dinates (pure $s$-coordinate), 
     153Note that when the bottom topography is entirely represented by the $s$-coordinates (pure $s$-coordinate), 
    154154the lateral boundary condition on tangential velocity is of much less importance as 
    155155it is only applied next to the coast where the minimum water depth can be quite shallow. 
     
    408408Options are defined through the \nam{bdy} \nam{bdy\_dta} namelist variables. 
    409409The BDY module is the core implementation of open boundary conditions for regional configurations on 
    410 temperature, salinity, barotropic and baroclinic velocities, as well as ice concentration, ice and snow thicknesses). 
     410temperature, salinity, barotropic and baroclinic velocities, as well as ice concentration, ice and snow thicknesses. 
    411411 
    412412The BDY module was modelled on the OBC module (see \NEMO\ 3.4) and shares many features and 
    413413a similar coding structure \citep{chanut_rpt05}. 
    414414The specification of the location of the open boundary is completely flexible and 
    415 allows for example the open boundary to follow an isobath or other irregular contour. 
     415allows any type of setup, from regular boundaries to irregular contour (it includes the possibility to set an open boundary able to follow an isobath). 
    416416Boundary data files used with versions of \NEMO\ prior to Version 3.4 may need to be re-ordered to work with this version. 
    417417See the section on the Input Boundary Data Files for details. 
     
    461461 
    462462If external boundary data is required then the \nam{bdy\_dta} namelist must be defined. 
    463 One \nam{bdy\_dta} namelist is required for each boundary set in the order in which 
    464 the boundary sets are defined in nambdy. 
     463One \nam{bdy\_dta} namelist is required for each boundary set, adopting the same order of indexes in which the boundary sets are defined in nambdy. 
    465464In the example given, two boundary sets have been defined. The first one is reading data file in the \nam{bdy\_dta} namelist shown above 
    466 and the second one is using data from intial condition (no namelist bloc needed). 
     465and the second one is using data from intial condition (no namelist block needed). 
    467466The boundary data is read in using the fldread module, 
    468467so the \nam{bdy\_dta} namelist is in the format required for fldread. 
    469 For each variable required, the filename, the frequency of the files and 
    470 the frequency of the data in the files is given. 
     468For each required variable, the filename, the frequency of the files and 
     469the frequency of the data in the files are given. 
    471470Also whether or not time-interpolation is required and whether the data is climatological (time-cyclic) data.\\ 
    472471 
     
    479478the latter used to make any adjustment to the velocity fields due to differences in the total water depths between the two vertical grids.\\ 
    480479 
    481 In the example namelists given, two boundary sets are defined. 
     480In the example of given namelists, two boundary sets are defined. 
    482481The first set is defined via a file and applies FRS conditions to temperature and salinity and 
    483482Flather conditions to the barotropic variables. No condition specified for the baroclinic velocity and sea-ice. 
     
    616615Each open boundary set is defined as a list of points. 
    617616The information is stored in the arrays $nbi$, $nbj$, and $nbr$ in the $idx\_bdy$ structure. 
    618 The $nbi$ and $nbj$ arrays define the local $(i,j)$ indices of each point in the boundary zone and 
    619 the $nbr$ array defines the discrete distance from the boundary with $nbr=1$ meaning that 
    620 the point is next to the edge of the model domain and $nbr>1$ showing that 
    621 the point is increasingly further away from the edge of the model domain. 
     617The $nbi$ and $nbj$ arrays define the local $(i,j)$ indexes of each point in the boundary zone and 
     618the $nbr$ array defines the discrete distance from the boundary: $nbr=1$ means that 
     619the boundary point is next to the edge of the model domain, while $nbr>1$ means that 
     620the boundary point is increasingly further away from the edge of the model domain. 
    622621A set of $nbi$, $nbj$, and $nbr$ arrays is defined for each of the $T$, $U$ and $V$ grids. 
    623622Figure \autoref{fig:LBC_bdy_geom} shows an example of an irregular boundary. 
     
    626625by reading in a ``\ifile{coordinates.bdy}'' file. 
    627626The nambdy\_index namelist defines a series of straight-line segments for north, east, south and west boundaries. 
    628 One nambdy\_index namelist bloc is needed for each boundary condition defined by indexes. 
     627One nambdy\_index namelist block is needed for each boundary condition defined by indexes. 
    629628For the northern boundary, \texttt{nbdysegn} gives the number of segments, 
    630629\jp{jpjnob} gives the $j$ index for each segment and \jp{jpindt} and 
     
    634633 
    635634The boundary geometry may also be defined from a ``\ifile{coordinates.bdy}'' file. 
    636 Figure \autoref{fig:LBC_nc_header} gives an example of the header information from such a file. 
     635Figure \autoref{fig:LBC_nc_header} gives an example of the header information from such a file, based on the description of geometrical setup given above. 
    637636The file should contain the index arrays for each of the $T$, $U$ and $V$ grids. 
    638637The arrays must be in order of increasing $nbr$. 
     
    644643For some choices of irregular boundary the model domain may contain areas of ocean which 
    645644are not part of the computational domain. 
    646 For example if an open boundary is defined along an isobath, say at the shelf break, 
     645For example, if an open boundary is defined along an isobath, say at the shelf break, 
    647646then the areas of ocean outside of this boundary will need to be masked out. 
    648647This can be done by reading a mask file defined as \np{cn\_mask\_file} in the nam\_bdy namelist. 
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