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 algorithm description

TMI specific details:

Information from the additional 10.65 GHz channels is used for intense rainfall scenes where the higher frequency channels begin to saturate. The change in the water vapor channel to 21.3 GHz also varies from the SSM/I retrieval as does the resolution of the sensor. The higher resolution of the TMI sensor (30x18 km vs. 69x43 km for the 19 GHz channels) decreases the impact of partial beam-filling, although it remains a significant issue.

Input Brightness Temperature Data:

The rainfall products provided here are computed from the Level 1C 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 the rainfall estimates from TMI are limited to the tropics, extending from approximately 38S to 38N.

Rainfall Data:

Daily and monthly gridded rainfall data is available via ftp. Details on the file format are also provided.
                FTP Rainfall Data
File Format for Daily Gridded Rainfall Files
                File Format for Monthly Gridded Rainfall Files

Rainfall Images:

Browse images in png format have been created for both the daily and monthly gridded rainfall data products.
                Create Daily Rainfall Images
Create Monthly Rainfall Images
FTP Pre-rendered Rainfall Images


Software to read the binary data files is available in both C and IDL.

    Get software

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.

Related Links:

Goddard Data and Information Services Center (DISC)