program rd_ascii
c
c   program to create an ascii version of the gridded fields at upper levels
c
c   Useage:
c   g77 read_ascii_grd.f -o read_ascii_grd.x
c
c   the data is stored using the following convention 
c   i - longitude, lon(i) =  80. + (i-1)*2. where i goes from 1, 26
c   j - latitude,  lat(j) =   0. + (j-1)*2. where j goes from 1, 21
c   k - pressure level,  from 1000 to 25mb
c       plev(k) = 1000. - (k-1)*25. where k goes from 1, 40
c

      integer    i, j, k
      integer    imax,    jmax,    kmax
      parameter (imax=26, jmax=21, kmax=40, gridsp=2.)
      parameter(rlat=0., rlon=80.)
      real wlon, elon, slat, nlat, gridsp, plev(kmax)

      real ps(imax,jmax), psl(imax,jmax)

c   upper air fields

      real t(imax,jmax,kmax), u(imax,jmax,kmax)
      real v(imax,jmax,kmax), q(imax,jmax,kmax)
      integer z(imax,jmax,kmax)

      real lat(jmax), lon(imax)
      character header*20, tmp*8

c   define pressure levels for data

      dp = 25.
      do k=1,kmax
         plev(k) = 1000. - (k-1)*dp
      enddo 

c   define lat/lon coordinates of the data

c   define latitude of all points
      do j=1,jmax
         lat(j) = rlat + gridsp*(j-1)
      enddo

c   define longitude of all points
      do i=1,imax
         lon(i) = rlon + gridsp*(i-1)
      enddo
C

      print *, 'Specify date/time to read (e.g., 98050100) >'
      read(5,'(a8)') tmp
   10 format(4x,a8)
      print *, ' reading grids for ', tmp

      open (20,file='gridded.'//tmp, status='unknown', form='formatted')

c   ********** read in upper level fields  ***********************************

      open(21, file='u.'//tmp, status='old', form='formatted')
      open(22, file='v.'//tmp, status='old', form='formatted')
      open(23, file='q.'//tmp, status='old', form='formatted')
      open(24, file='t.'//tmp, status='old', form='formatted')
      open(25, file='z.'//tmp, status='old', form='formatted')

c   read in zonal wind component (m/s) 

      do k=1,kmax
         read (21,'(a20)') header 
         write(20,'(a20)') header
         write(20,45) (ifix(lat(j)),j=1,jmax)
         do i=1,imax
            read  (21,50) (u(i,j,k),j=1,jmax)
            write (20,51) ifix(lon(i)), (u(i,j,k),j=1,jmax)
         enddo
      enddo

c   read in meridional wind component (m/s)

      do k=1,kmax
         read (22,'(a20)') header 
         write(20,'(a20)') header
         write(20,45) (ifix(lat(j)),j=1,jmax)
         do i=1,imax
             read (22,50) (v(i,j,k),j=1,jmax)
             write(20,51) ifix(lon(i)), (v(i,j,k),j=1,jmax)
         enddo
      enddo

c   read in specific humidity (gr/kg) 

      do k=1,kmax
         read (23,'(a20)') header 
         write(20,'(a20)') header
         write(20,45) (ifix(lat(j)),j=1,jmax)
         do i=1,imax
             read (23,60)  (q(i,j,k),j=1,jmax)
             write(20,61)  ifix(lon(i)), (q(i,j,k),j=1,jmax)
         enddo
      enddo

c   read in temperature (C) 

      do k=1,kmax
         read (24,'(a20)') header 
         write(20,'(a20)') header
         write(20,45) (ifix(lat(j)),j=1,jmax)
         do i=1,imax
             read (24,50) (t(i,j,k),j=1,jmax)
             write(20,51) ifix(lon(i)), (t(i,j,k),j=1,jmax)
         enddo
      enddo

c   read in geopotential height (m) 

      do k=1,kmax
         read (25,'(a20)') header 
         write(20,'(a20)') header
         write(20,45) (ifix(lat(j)),j=1,jmax)
         do i=1,imax
             read (25,40) (z(i,j,k), j=1,jmax)
             write(20,41) ifix(lon(i)), (z(i,j,k), j=1,jmax)
         enddo
      enddo

      close(21)
      close(22)
      close(23)
      close(24)
      close(25)

   40 format(21i6)
   41 format(22i6)
   45 format(6x,21i6)
   50 format(21f6.1)
   51 format(i6,21f6.1)
   60 format(21f6.2)
   61 format(i6,21f6.2)

      end