The Global Precipitation Climatology Project daily precipitation was obtained from National Climatic Data Center (NCDC). The precipitation estimates are derived by different methods in the tropics and the extratropics, and the documentation available from the above WWW page provides a detailed discussion and reference.
A comparison of the Climate Prediction Center Merged Analysis of
Precipitation (CMAP) and GPCP merged precipitation datasets is given
by:
Yin, X., A. Gruber, and P. Arkinc, 2004: Comparison of the GPCP
and CMAP Merged Gauge-Satellite Monthly Precipitation Products for the
Period 1979-2001. J. Hydromet., 5, 1207-1222.
The GPCP is managed by Arnold Gruber, and it is a component of the Global Energy and Water Cycle Experiment of the World Climate Research Program. GPCP is an ongoing project, and updates and new algorithms are always being developed, so users are advised to to check the NCDC GPCP WWW page and NASA Goddard Space Flight Center to see if there is a newer product that replaces this one. The updates of the data seem to lag reality by 2-3 months. I will not be updating the netCDF version of this data set until I have a need for updated data. Please send questions or comments about the product to George Huffman.
The data:
Reference:
Huffman, G. J.,R. F. Adler, M. M. Morrissey, S. Curtis, R. Joyce,
B. McGavock, and J. Susskind, 2001: Global precipitation at
one-degree daily resolution from multi-satellite observations.
J. Hydrometeor., 2, 36-50.