Documentation for GPCP Satellite-Derived (IR) GPI Daily Rainfall
  Products in Pentad format:

     Each file contains data for 1 pentad ( 5 days ) for 1x1 degree
  resolution grid. The data are stored in 360 x 80 arrays and each
  value represents the estimated areal average data for 1x1 degree
  "box". Missing values are identified as "-9999". The array
  orientation is:

  40N  ----------------------------      -----------------
       |       |       |       |         |       |       |
       | (1,1) | (2,1) | (3,1) |   . . . |(359,1)| (360,1)
       |       |       |       |         |       |       |
  39N  ----------------------------      -----------------
       |       |       |       |         |       |       |
       | (1,2) | (2,2) | (3,2) |   . . . |(359,2)| (360,2)
       |       |       |       |         |       |       |
                                     .
                                     .
                                     .
  39S  ----------------------------      -----------------
       |       |       |       |         |       |       |
       | (1,80)| (2,80)| (3,80)|   . . . |(359,80) (360,80)
       |       |       |       |         |       |       |
 40S   ----------------------------      -----------------
       |       |       |       |         |       |       |
       0      1E      2E      3E        2W      1W       0


    The data in the file are:
 
    First day of the pentad: daily rainfall estimates ( gpi )
                             daily satellite indentification 
                             daily number of satellite observations;

    Second day of the pentad: daily rainfall estimates ( gpi )
                              daily satellite indentification
                              daily number of satellite observations;
    .
    .
    .
    .
     
    Fifth day of the pentad:  daily rainfall estimates ( gpi )
    ( or sixth for the 12th   daily satellite indentification
      pentad of leap year )   daily number of satellite observations.

    Units for rainfall estimates are mm/day.
    The satellite identifiers represent the satellite used to obtain
 information needed to produce the GPI estimate for a given 1x1 degree
 box for that day:

     1 = GMS
     2 = GOES WEST
     3 = GOES EAST
     4 = METEOSAT ( METEOSAT-7 )
     5 = INSAT ( METEOSAT-5 )
     6 = NOAA 12 ( Daytime Pass )
     7 = NOAA 12 ( Nighttime Pass )
     8 = NOAA 14 ( Daytime Pass )
     9 = NOAA 14 ( Nighttime Pass )

    The number of satellite observations is the number of satellite
 observations within a day used to derive the GPI estimate for a given
 1x1 degree box for that day.
 
    The name of file is IRPROD_yyyypp where yyyy is the year (i.e. 1998)
 and pp is the number of the pentad.

      The data can be read in FORTRAN as follows:

      real*4       gpi(360,80),satid(360,80),numobs(360,80)

        open (unit = 17, file = filename, form = 'unformatted',
     1        access = 'direct', recl = 360*80*4)

      iwrec = 0

      iyr=iyyyypp/100

      if(mod(iyr,4).eq.0.and.ipnt.eq.12)then
       ipntmx=6
      else
       ipntmx=5
      endif

      do ipday=1,ipntmx

      iwrec = iwrec + 1
      read(17,rec = iwrec) ((gpi(i,j),i=1,360),j=1,80)
      iwrec = iwrec + 1
      read(17,rec = iwrec) ((satid(i,j),i=1,360),j=1,80)
      iwrec = iwrec + 1
      read(17,rec = iwrec) ((numobs(i,j),i=1,360),j=1,80)

     enddo

    We will update these data approximately once a month.