GRID MASKS FOR THE NMC
                3-D TEMPERATURE AND VELOCITY FIELDS

Masks that identify grid points which have valid temperature and
velocity data are necessary to properly interpret the NMC analyzed
fields.  The mask for the temperature grids is equivalent to the model
land and ocean bottom mask.  Since the velocity grid is geographically
offset and its computation is dependent on the surrounding temperature
field the velocity mask is different and does not represent the ocean
bottom as accurately as the temperature mask. For both masks, the value
at each grid point is the number of valid ocean model levels, e.g. 0 =
land surface (no model levels, 27 = 27 ocean model levels have valid
data at a particular grid point.

Both masks are given as a two dimensional longitude by latitude arrays
(112 x 81) matching the grid fields for the temperature and velocity
data.  The Fortran program below illustrates how to read the mask data
files.  


      program readmask
      integer  tmask(112,81),uvmask(112,81)

      open(10,file='mask.tuv',
     1form='formatted',status='unknown')

      read(10,'(112i2)') tmask
      read(10,'(112i2)') uvmask

      end