Offline nesting routines for HYCOM 2.1

NB: Some of these may/may not work. Offline nesting wasn't that much used in 
    2.1, so I will focus on streamlining  these features for the 2.2 version.


MERCATOR routines
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Intermediate procedure to create  restart files from
Mercator fields:

1) You need a restart file from the hycom run (any restart file will do,
   since the time-independent fields "psikk" and "thkk" are needed)

2) Create horizontal interpolation of Mercator fields to hycom grid. 
   This is done with the routine "hint_mercator" (you obviously need
   MERCATOR files for this)

3) Do vertical remapping of the Mercator fields, this is done with
   the routine "vremap_mercator".

You now have a restart file interpolated from the mercator grid. This can be used
to extract fields to nesting variables. (Can also restart from it)
PS:For step 2-3, the routine mercator_to_hycom.sh may be used




Procedure to create NERSC nesting files from hycom files (2.1 for now)
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Procedure to create nesting files from Mercator (or ordinary hycom restart)  files:
1) Produce hycom restart files from the Mercator files (if thats what you have!)
   This step does all the v/h interpolation needed to create "sane" 
   restart files. Make sure that the model to be nested to was run with the
   "NEST_INNER" CPP flag set, otherwise the bathymetry used in the interpolation 
   may be wrong.

2) List the restart files you want to create nesting conditions for in "nestoffline.in". 
   Only list the ".a" files

3) Run the program "nestoffline", works on restart files and weekly average files.

4) The subdirectory "Nest" will now be populated with nesting files.




Procedure to USE these nesting files in hycom. So far the HYCOM code to do this is not in the CVS. 
##################################################################################################

1) Make sure NEST_INNER and NEST_OFFLINE  is set in MODEL.CPP, compile the model.

2) In the Nest catalogue where the model is running, create the file "nest.files". 
   This files lists all the nesting files (and times) which will be used by the model.
   Only list the ".hdr" files in this file.

3) Run the model, and replace the line with lnesti/nestdti with "T OFFLINE".