TRMM Microwave Imager (TMI) Rainfall Products

Sensor Description:

The TMI is a nine-channel passive microwave radiometer based upon the Special Sensor Microwave/Imager (SSM/I). The key differences are the addition of a pair of 10.7-GHz channels with horizontal and vertic al polarizations and a frequency change of the water vapor channel from 22.235 to 21.3 GHz. This change off the center of the water vapor line was made in order to avoid saturation in the tropical orbit of TRMM. In addition, the TMI has significantly higher spatial resolution than SSM/I due to the lower orbit of the TRMM satellite.

Algorithm Description:

GPROF 2010: The rainfall algorithm used to compute rainfall estimates from the TMI brightness temperature data is the 2010 release of the Goddard PROFiling algorithm (GPROF) [Kummerow et al., 2001, Masunaga and Kummerow, 2005]. The TMI version of GPROF is run operationally by the Precipitation Processing System (PPS) and is referred to as the 2A12 algorithm. The current plan is for the PPS to begin processing GPROF 2010, also referred to as 2A12 version 7, once the algorithm is finalized in late 2010. Additional information is available on the TMI implementation details.

Version Information:
  • GPR08.B2 (GPROF 2008 beta version 2): Preliminary version of GPROF 2008 for TMI.
  • GPR08.B3 (GPROF 2008 beta version 3): Minor changes were made to the level 2 output including a few bug fixes, however, the gridded data files are basically unchanged from version B2.
  • GPR08.B4 (GPROF 2008 beta version 4): A number of changes were made to the level 2 output including the addition of a data quality flag. There are significant changes in the output data fields particularly with respect to rainfall estimates over land and coast.
  • GPR08.B5 (GPROF 2008 beta version 5): Minor changes were made to the level 2 output, but no significant changes were made to the daily and monthly gridded output products. As a result, the gridded products on this site were not updated to B5.
  • GPR08.B6 (GPROF 2008 beta version 6): B6 is a beta version 6. Changes to the level 2 output include a number of bug fixes along with the following improvements/changes. These include an improvement to the sea-ice edge detection algorithm, the use of higher resolution (0.25x0.25 degree) daily Reynolds SST data, and changes to the channel weights based on individual channel errors. To improve the consistency between rainfall estimates from different sensors a modification was made to the rain screening methodology used in the optimal estimation procedure for retrieving geophysical paramters over non-raining scenes. Finally, for sensors other than TMI several adjustments were made to the apriori databases to improve the consistency in the output rainfall estimates.
  • GPR10.V1 (GPROF 2010 version 1): The apriori database was finalized based on the TRMM version 7 products.
  • GPR10.V2 (GPROF 2010 version 2): A number of updates were made to the V1 retrieval to improve consistency between sensor and screen for desert on snow-covered regions over land. The land retrievals have been updated and are now available for all the sensors.

Input Brightness Temperature Data:

The rainfall products provided here are computed from the TRMM 1B11 version 7 brightness temperature dataset.

Data Availability:

The TRMM satellite was launched on November 27, 1997 with rainfall estimates available from December 8, 1997 through to the present. Because the inclination of TRMM is only 35 degrees the rainfall estimates from TMI are limited to the tropics, extending from approximately 38S to 38N.

Rainfall Data:

FTP Daily and Monthly Gridded Rainfall Data Files
File Format Specification for Daily Gridded Rainfall Files
File Format Specification for Monthly Gridded Rainfall Files

Rainfall Images:

Create/Display Daily Rainfall Images
Create/Display Monthly Rainfall Images
FTP Pre-rendered Rainfall Images


Get software to read the binary gridded rainfall files.

Additional Documentation/References:

–   Kummerow, C., W. Barnes, T. Kozu, J. Shiue, and J. Simpson, 1998: The Tropical Rainfall Measuring Mission (TRMM) sensor package, J. Atmos. Oceanic Technol., 15, 809-817.
–   Kummerow, C. and Coauthors, 2000: The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit, J. Appl. Meteor., 39, 1965-1982.
–   Kummerow, C., Y. Hong, W. S. Olson, S. Yang, R. F. Adler, J. McCollum, R. Ferraro, G. Petty, D. B. Shin, and T. T. Wilheit, 2001: The evolution of the Goddard profiling algorithm (GPROF) for rainfall estimation from passive microwave sensors, J. Appl. Meteor., 40, 1801-1820.
–   Masunaga, H. and C. D. Kummerow, 2005: Combined radar and radiometer analysis of precipitation profiles for a parametric retrieval algorithm, J. Atmos. Oceanic Technol., 22, 909-929.

Related Links:

Goddard Data and Information Services Center (DISC)