the mkgrid_tbase dataset is a binary dataset used for
generating clm topography.  it is a 5 minute dataset
with the following characteristics.

C  Read TerrainBase Earth surface elevation
C  The data are organized in full 360 degree latitude circles
C  beginning at 90N and steping southward to 89 55 S; the circle at
C  90N has constant value and the circle at 90S is not given, but a
C  value of 2810 meters may be assumed.
C
      integer nlon,nlat         ! 5-minute dimension
      parameter (nlon=4320,nlat=2160) 
      integer itopo(nlon,nlat+1)

      print *,'Read tbase start'
      open(20,file='tbase.dat',form='unformatted')
      read(20) itopo
      close(20)
      print *,'Read tbase completed'

in actuality, the dataset starts at 0E and 90N.  this dataset
was converted to netcdf using tbase_convert.F90.  see that code
for details.

(tcraig, may, 2006)