SUBROUTINE GRID(rlat,rlon,lat,lon,space)
 
C    CALCULATES GRID NUMBERS FROM INPUT LATITUDE AND LONGITUDE
 
c************************************************************
c
c    Passed Variables:
c
c     rlat,rlon - actual latitude and longitude
c     lat,lon - calculated grid box numbers
c     space - grid spacing (1.0 is a 1 degree latitude
c             by one degree longitude grid box)
c
c***********************************************************

      double precision spaced
      spaced=(space*1.D+00)+1.D-07

c**********************************************************
c
c     Calculate latitude grid number:
c
c      1. add 90 to actual latitude, since actual latitudes
c         run from -90 to 90, and grid numbers run from
c         1 to 180.
c
c      2. Divide by spacing.  The additional 1E-7 is to
c         insure that any latitude right on the line between
c         two grid boxes will be included in the smaller 
c         number grid box.
c     
c      3. Add one, since a grid number for actual latitude
c         -90 would be 0 otherwise.
c
c**********************************************************

      lat=(((rlat*1.D+00)+(90.*1.D+00))/spaced)+1.D+00
 
c**********************************************************
c
c    Calculate longitude grid number
c
c     1. Longitude grid numbers run from 1 to 360 while
c        actual longitudes run from -180 to 180.  The difference
c        from latitude is that negative values are converted
c        to the larger end of longitude grid numbers.
c        They are converted to the values 181 to 360. 
c
c**********************************************************

      if (rlon.lt.0) then
       lon=(((rlon*1.D+00)+360.D+00)/spaced)+1.D+00
      else
       lon=((rlon*1.D+00)/spaced)+1.D+00
      endif
 
      return
      end