program read_int_sonde
c
c  This program reads interpolated soundings for SURFRAD stations
c
c  Filenames are of the form dd-mmm-yyyy_hh.int, e.g., 02-jun-1998_12.int
c  for 1200 UTC, June 2, 1998.
c
c  There is one header record for the file, which contains the number
c  of soundings to follow (ng), the number of lines per sounding 
c (num_levels),
c  the date and time in the format dd-mmm-yyyy_hh:mm:ss.dd, the number
c  of passes carried out in the weighted sum interpolation (npass), and 
c  the scale length in kilometers (xl) used in the interpolation.  The scale 
c  length is defined as the distance from the observation that its weight 
c  falls to 1/e.   A Gaussian weighting function is used.  In the interpolated 
c  sounding files before 1997, npass and xl may be missing from the initial
c  header record.  In those cases, as in all, four passes and a scale length of 
c  400 km were used.   
c
c  The file header is followed by the soundings.  Each sounding has a
c  header of its own that contains the station name, latitude,
c  longitude, and elevation above sea level in meters.  The 
c  The convention used for the earth coordinate system is North lat.
c  and East Long. are positive, and South Lat. and West Long. are  
c  negative. 
c
c  All interpolated soundings have 38 levels, so num_levels should always
c  be 38.  The first level is always the surface, and it is followed by
c  37 upper levels at 25 mb increments to 100 mb.  These upper levels 
c  always begin with 1000 mb, then 975 mb, 950 mb ... 100 mb.  Whenever
c  a level is below the surface, they are filled with missing values
c  (-999.0).  
c
c  There are usually 7 soundings per file, 6 corresponding to the 
c  six surfrad stations and one to the Central Facility of the ARM
c  SGP site 
c
c  This fortran code may be used to read the interpolated sounding files.
c  Units are given in subroutine readsond.
c
      parameter (nc=50)
c
      common/unit/lun_in
c
      real*4 pres(nc),dwpt(nc),temp(nc)
      real*4 height(nc),u(nc),v(nc)
c
      character stat*20, datetime*20
      character*80 filename
      character*24 atime
c
      data badval /-999.0/
c
c Define unit numbers
      lun_in = 15
c
c open the interpolated sounding file
c
c inquire about the name of the interpolated soundings file
      write(6,5)
  5   format(1x,/)
      write(6,7)
  7   format(1x,'enter the name of the interpolated sounding file')
      read(5,10)ina,filename ! ina is the length of the character string 
just read in
  10  format(q,a)
      write(6,12) filename(1:ina)
  12  format(/,1x,'filename requested is ',a)
c
      open(lun_in,file=filename(1:ina),status='old',err=120)
c
c read file header record
      read(lun_in,15) ng,num_levels,atime,npass,xl
 15   format(1x,i4,1x,i3,1x,a24,1x,i2,1x,f8.2)
c
c set the dat label for the plot
      datetime = atime(1:17)
c
c read one sounding
c
  20  call readsond(num_levels,pres,temp,dwpt,u,v,height,
     1  datetime,stat,badval)
      write(6,25) stat
  25  format(/,1x,'Sounding for ',a,' read')
c
      do i=1,num_levels
         write(6,30)pres(i),height(i),temp(i),dwpt(i),u(i),v(i)
  30     format(6(1x,f8.2))
      enddo
c
      go to 20 ! read the next sounding
c
c ERROR- could not open the requested file
c
 120  write(6,40) filename(1:ina)
  40  format(1x,/,'Sounding file ',a,' could not be opened')
c
      end
c-------------------------------------------------------------------------
      subroutine readsond(num_levels,pres,temp,dwpt,u,v,
     1 height,datetime,stat,badval)
c
      common/unit/lun_in ! logical unit number for input file
c
c  the input file is assumed to be open and assigned to lun "lun_in"
c
c output arrays:
      real*4      pres(num_levels)   ! pressure in (mb)
      real*4      height(num_levels) ! geopotential height (m)
      real*4      temp(num_levels)   ! temperature (C)
      real*4      dwpt(num_levels)   ! dew point temperature (C)
      real*4      u   (num_levels)   ! u component (m/s)
      real*4      v   (num_levels)   ! v component (m/s)
c
      character stat*20, datetime*20
      character*16 surfname
c
c read the sounding header
      read(lun_in,10,end=30) surfname,g_lat,g_lon,ielev
  10  format(1x,a16,1x,f6.3,1x,f8.3,1x,i4)
c
c load the station name into variable stat
      stat(1:16) = surfname
c
      do i = 1,num_levels
         read(lun_in,20) xpres,xheight,xtemp,xdewpt,xu,xv
  20     format(6(1x,f8.2))
         if(xpres.ne.badval)then
            pres(i) = xpres
         else
            pres(i) = badval
         endif
         if(xheight.ne.badval)then
            height(i) = xheight
         else
            height(i) = badval
         endif
         if(xtemp.ne.badval)then
            temp(i) = xtemp
         else
            temp(i) = badval
         endif
         if(xdewpt.ne.badval)then
            dwpt(i) = xdewpt
         else
            dwpt(i) = badval
         endif
         if((xu.ne.badval).and.(xv.ne.badval)) then
            u(i) = xu
            v(i) = xv
         else
            u(i) = badval
            v(i) = badval
         endif
      enddo
      return
c
  30  write(6,40)
  40  format(/,1x,'no more soundings in this file, stop')
c
      call exit(0) !stop
c
      end
c------------------------------------------------------------------------