[MITgcm-support] nudging techniques, OBCS and freezing

[Ed Hill]

On Sun, 2004-08-15 at 10:30, prosperi at wicc.weizmann.ac.il wrote:

> #define ALLOW_OBCS
> in CPP_OPTIONS.h  and activate it with use_OBCS=.TRUE, in namelist 
> PACKAGES of input/data.pkg.
> If I do it I get from the genmake that this definiton is not anymore 
> allowed.
> If I want to put OBCs at a southern part of my domain, how can I do it? 

The current docs do describe how to add packages at compile time and how
to turn them on/off at run-time:

  http://mitgcm.org/sealion/online_documents/node190.html

But just to give a concrete example, to add the "obcs" package, put its
name in the file packages.conf as you see in the plume_on_slope example:

  MITgcm/verification/plume_on_slope/code/packages.conf

Then, once compiled into the code, turn it on/off at run-time by setting
the flags in "data.pkg".  Again, see:

  MITgcm/verification/plume_on_slope/input/data.pkg

for an example.  Setting the obcs information is also shown in
plume_on_slope in the "data.obcs" file.


> 2) I am confused about something very basic:
>    in a finite volume integration scheme u have the advantage that 
> increaing the horizontal resolution, u automatuically resolve better even 
> the topography since u are working with volume units. When I set the size 
> of the grid and the domain decomposition, I have, basically (...very 
> basically), two files to change:
> 
> SIZE.h (nSx, nSy, nr) and in data delX = nSx*size of the grid.
> hFacMin gives me  the actual thickness of the cell.
> The question is:
> is it eventually by hFacMin that I can increase the spatial resolution of 
> my domain?

You'll probably bump into other (practical) limits first such as:

 - storage space (RAM)
 - small time steps (stability limits which are tied to 
    the size of the grid elements)

Ed

-- 
Edward H. Hill III, PhD
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