program read_ssmi
c
c   Sample program showing read statements used to read in SSMI data.
c
c   The SSMI data is on a 1080 X 540 element grid with the origin at
c   90N latitude and 0 degrees longitude.  There are 12 monthly data
c   files for 1992.
c
c





      integer*2 spd(1080,540)   ! SSMI data in cm/sec.
                                ! -9999 indicates land
                                ! 9999 indicates no data

      integer*2 iyr,imon        ! year and month of data set

      real*4 xmin,xmax          ! minimum and maximum speeds in data in m/sec


 
      real j_to_lat, i_to_lon      ! conversion functions
      integer lat_to_j, lon_to_i



      open(8,file='spd9201.dat',form='unformatted')
      read(8) iyr,imon
      write(*,*) iyr,imon	  ! should be 92 and 1 for first SSMI file
      read(8) xmin,xmax
      write(*,*) xmin,xmax        ! in this case should be 0.19 and 17.35
      read(8) spd
      close(8)

      stop
      end



c
c
c  The following four functions can be used convert    grid  <----> lat/lon.
c
c

 
      integer function lat_to_j(lat)
c
c     Function takes a latitude and returns the index of the grid row that
c     latitude falls in.  NOTE: assumes 540 grid cells over 180 degrees and
c     that latitude varies from -90 to 90.
c
      real lat
      lat_to_j=int((90.-lat)*3.0)+1
      return
      end




      integer function lon_to_i(lon)
c
c     Function takes a longitude and returns the index of the grid column
c     that the longitude falls in.  NOTE: assumes 1080 grid cells over 360
c     degrees and that longitude varies from 0 to 360.
c
      real lon
      lon_to_i=int(lon*3.0)+1
      return
      end



      real function j_to_lat(j)
c
c     Function takes the index of a grid row and returns the latitude of the
c     center of the grid cells in that row.  NOTE: assumes 540 grid cells
c     over 180 degrees and that latitude varies from -90 to 90.
c
      integer j
      j_to_lat=90.-((float(j)-.5)/3.0)
      return
      end



      real function i_to_lon(i)
c
c     Function takes the index of a grid column and returns the longitude of
c     the center of the grid cells in that column.  NOTE: assumes 1080 grid
c     cells over 360 degrees and that longitude varies from 0 to 360.
c
      integer i
      i_to_lon=(float(i)-.5)/3.0
      return
      end