JISAO data

GOES Precipitation Index (GPI)

The GPI is available in monthly, pentad, and daily averages. This WWW page has the monthly values, but the other temporal resolutions are available from the NCEP Climate Prediction Center ftp site.

Annual Total Precipitation (m) 1986-95
Image of tropical domain
Annual total GPI rainfall is characterized by rainfall in excess of 3 m over the equatorial landmasses, the ITCZ and SPCZ, the eastern portion of the Indian Ocean. The largest totals, in excess of 4 meters, are found near islands and the Isthmus of Panama.

The GOES precipitation index estimates tropical rainfall using cloud-top temperature -- see the CPC WWW page. The GPI rainfall estimates are prepared by Robert Joyce of NOAA NCEP, and span the latitudes within 40 degrees latitude of the equator north and south. This version of the GPI has been processed to reduce longitudinal discontinuities associated with different satellites, and other corrections have also been applied (Joyce and Arkin, 1997). Questions concerning the method should be directed to Robert Joyce.

The data:

  • The data in netCDF format (1.2 Mbytes) (mm day-1). Obtained on 28 October 1996. Maps of "NaN"s are appended to the end of the file so that the file is for complete years.
    The same data, but in units of mm month-1 (netCDF format) (1.2 Mbytes). Obtained on 28 October 1996. Maps of "NaN"s are appended to the end of the file so that the file is for complete years.
    All errors in the netCDF file are due to Todd Mitchell.
  • Monthly values were produced through February 2004, and they can be obtained at the NCEP anonymous ftp directory

    Climatological fields for 1986-95 in netCDF:
    monthly climatology The time variable was written incorrectly. The first month is January, the second month is February, and so on.
    annual total


  • Janowiak, J. E., and P. A. Arkin, 1991: Rainfall variations in the tropics during 1986-1989, as estimated from observations of cloud-top temperature. J.Geophys. Res., 96 Suppl., 3359-3373.
  • Joyce, R., and P. A. Arkin, 1997: Improved estimates of tropical and subtropical precipitation using the GOES Precipitation Index. J. Atmos. Ocean. Tech., 10, 997-1011.
  • Online documenation.


    September 1998
    Todd Mitchell (mitchell@atmos.washington.edu)
    JISAO data