TRMM Monthly 0.5° x 0.5° Combined Rainfall (3B31)


This dataset is created from the TRMM products 2A12 and 2B31 in the GSFC Earth Sciences (GES) Distributed Active Archive Center (DAAC), NASA. The data of 2B31 is the combination data from the TMI (TRMM Microwave Imager) and PR (TRMM Precipitation Radar). The PR measures the 3-D rainfall distribution over both land and ocean, and defines the layer depth of the precipitation. The TMI is a nine-channel passive microwave radiometer, which builds on the heritage of the Special Sensor Microwave/Imager (SSM/I) instrument flown aboard the Defense Meteorological Satellite Program (DMSP) platforms.

The data of 2A12 is the TMI Level 2 Hydrometeor Profile Product. It includes the vertical profiles of hydrometeors from TMI brightness temperatures by blending the radiometric data with dynamical cloud models. For each pixel, the algorithm assigns a surface type (land/ocean/coast) and a freezing height; and computes surface rain, convective surface rain, and profiles of hydrometeors (cloud liquid, cloud ice, water vapor, etc.) at 14 vertical levels.

Output data of 2A12 and 2B31 are input to the 3B31 and then accumulated for each month at 0.5 grid elements. Monthly surface rainfall totals are derived by multiplying the mean rainfall rate by the total number of hours in each month. Because the rain water content profile of 2A12 and rain rate profile of 2B31 are output at different vertical resolutions, averaging the outputs of 2B31 over several radar range gates to match the 14 layers of 2A12 is necessary. Also, the rain rate (mm/hr) at each radar gate in 2B31 is converted into rain water content (g/m3) to match that in 2A12.

IMPORTANT: After over 17 years of productive data gathering, the instruments on TRMM were turned off on April 8, 2015.

Read the TRMM end of mission frequently asked questions

rain water content from 2a12 [gm**-3]
surface precipitation from 2a12 accumulated in box [mm]
sonvective surface precipitation from 2a12 accumulated in box [mm]
snow liquid water content from 2a12 [gm**-3]
graupel liquid water content from 2a12 [gm**-3]
the number of pixels with pixelstatus equal to zero
surface precipitation from 2b31 accumulated in box [mm]
rain water content from 2b31 [gm**-3]
snow liquid water content from 2b31 [gm**-3]
graupel liquid water content from 2b31 [gm**-3]
the number of pixels npixtotalcomb
the ratio of 2b31 (narrow swath) to 2a12 (wide swath) surface precipitation
the ratio of 2b31 to 2a12 surf. precip., from the overlap region (where both have valid samples)
Zonal Global by 0.5 deg
Meridional 40S to 39.5N by 0.5 deg
Vertical 28 levels
Temporal Dec 1997 to Mar 2015 by 1 month (Orbit descent: Nov 2014-Jan15 missing)
Static? yes
Acquired Jul 17, 2003 (Updated Sept 2015)
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