Running gnumake in this directory will create an executable named "mkrgrid"
in $(HOME)/bin.  Its function is to take an input CAM history tape (netcdf
format) and interpolate it either from a full grid to a reduced grid (the
default), or from a reduced grid to a full grid ("-r" option).  When going
full->reduced, a namelist defining the reduced grid must be specified to be
read from stdin.  An example namelist for a 1-digit grid (nl.r1up) is
contained in this directory.  When coverting reduced->full, no namelist is
needed as this information is contained in the netcdf history file.

Default interpolation is linear (-l).  Other options available are Fourier
(-f), cubic (-c), and monotonic cubic (-m field_name).  Fourier and cubic
options apply to the entire file, while monotonic cubic must be specified on
a field by field basis.

An example usage might be:

mkrgrid h0001.nc h0001.reduced.nc < nl.r1up

then to reverse the operation:

mkrgrid -r h0001.reduced.nc h0001.nc


