The Global Precipitation Climatology Project (GPCP) reanalyzed their archive
of surface rain gauge data to produce a 1 deg. x 1 deg. monthly precipitation
product for 1987-1988. The standard land/sea mask was applied by the
publication group at NASA GSFC. The Global Runoff Data Center (GRDC)
contributed monthly river runoff rate data for 14 basins together with
information on the location of the gauges and the catchment area upstream of
the gauge. The percentage of each 1 deg. x 1 deg. grid area covered by lakes,
rivers, and marshes was obtained from data published by Cogley (1991).
The Food and Agricultural Organization (FAO) archive on soil properties has
been extensively scrutinized by researchers at the University of Arizona
(Sorooshian, Amer), NASA GSFC (Koster) and at NASA GISS (Zobler). These
analyses were combined to create consistent global fields of soil texture,
depth, and slope.