TRMM Combination

The Tropical Rainfall Measurement Mission (TRMM) is being flown by the National Aeronautics and Space Administration (NASA, U.S.) and the Japan Aerospace Exploration Agency (JAXA, Japan) to improve our quantitative knowledge of the 3-dimensional distribution of precipitation in the tropics. TRMM has a passive microwave radiometer (TRMM Microwave Imager, TMI), the first active space-borne Precipitation Radar (PR), a Visible-Infrared Scanner (VIRS), and other instruments. Coordinated observations are intended to result in a "flying raingauge" capability.

Two of the products produced operationally in TRMM are the "TRMM and Other Satellites" precipitation estimate (product 3B42) and the "TRMM and Other Sources" precipitation estimate (product 3B43) described in Huffman et al. (2007). The TRMM Multi-satellite Precipitation Analysis (TMPA) algorithm calibrates the TMI (2A12), SSMI, SSMIS, AMSR-E, AMSU-B, MHS and IR precipitation estimates to the TRMM Combined Instrument (TCI, product 2B31, based on both TMI and PR data), and all of these are merged to produce 3-hourly multi-satellite precipitation fields. Algorithm 3B43 merges these multi-satellite estimates for a month with gauge data (mostly over land) to compute estimated monthly satellite-gauge precipitation. Finally, product 3B42 is computed by (approximately) scaling the 3-hourly multi-satellite data to sum to the monthly 3B43 satellite-gauge field. The data sets cover the period January 1998--present (with a two-month delay). Both 3B42 and 3B43 products are observation-only datasets. There are two fields in each data set - estimates of surface precipitation and RMS random error. Currently both 3B42 and 3B43 are being produced as Version 7.

The data set archive consists of binary data sets in Hierarchical Data Format (HDF). Each 3B42 file contains a 3-hourly estimate and each 3B43 file contains a one-month estimate. The grid on which each field of values is presented is a 0.25 deg x 0.25 deg latitude--longitude (Cylindrical Equal Distance) array of points over the latitude range 50N-S. It is size 400x1440, with X (latitude) incrementing most rapidly South to North, and then Y (longitude) incrementing West to East from the Date Line. Grid edges are located at whole-degree values:

First point center      = (49.875S,179.875W)
Second point center = (49.625S,179.625W)
Last point center      = (49.875N,179.875E)

Missing values are denoted by the value -9999.9, and the units are mm/hour.

Technical documentation is available though the "more information" hot link at the bottom of the page, and the standard reference is:

Huffman, G.J., R.F. Adler, D.T. Bolvin, G. Gu, E.J. Nelkin, K.P. Bowman,

E.F. Stocker, D.B. Wolff, 2007: The TRMM Multi-satellite Precipitation

Analysis: Quasi-Global, Multi-Year, Combined-Sensor Precipitation

Estimates at Fine Scale. J. Hydrometeor., 8, 33-55.

The dataset curator is:

 precip data set curator

David T. Bolvin
Code 612
NASA Goddard Space Flight Center
Greenbelt, MD 20771 USA
Phone: +1 301-614-6323
Fax: +1 301-614-5492

More Information (pdf)

Latest News (pdf)

See a list of publications (pdf)

Notice: End of TRMM, shift to GPM (pdf)