2A Radiometer (GPROF & PRPS)

The 2A GPROF and 2A PRPS algorithms estimate precipitation rate from single orbits brightness temperature data from passive-microwave radiometers.  The algorithms also uses ancillary information about Earth’s atmosphere and surface. The GPM archive contains 2A GPROF granules for the following instruments, whose satellite names are stated in parentheses in the following list: GMI (GPM), TMI (TRMM), SSMI (F11 through F15), SSMIS (F16, F17, F18), AMSUB (NOAA 16, 17, 18), AMSRE (Aqua), AMSR2 (GCOM W1), MHS (NOAA 18, 19, and 20; METOP A, B, C), and ATMS (NPP). The PRPS algorithm is run on the SAPHIR observations from the Megha-Tropiques satellite.

For instruments currently in orbit, there are near-realtime (NRT) products and standard-research products.  All instruments have climate products that are designated 2A-CLIM GPROF or 2A-CLIM PRPS.  The difference between climate products and standard-research products is that climate products use ancillary data that are not produced until approximately 3 months after the satellite observations are made.

Processing Level
Dates Covered
1991 - Present (varies based on satellite)
Data Simple Description
Single-orbit radiometer rainfall estimates from GPM GMI, TRMM TMI, and constellation microwave radiometers
Minimum Latency
2 hours (near real-time); 40 hours (Research); 3 months (Climate)
Spatial Resolution
5km x 8km (GMI 89GHz channels)
Varies by satellite and instrument channel
Current Algorithm Version
V05A, V05B, or V05C (2A GPROF for various satellites); V06A (2A PRPS for SAPHIR)
Date Last Updated
April 17th, 2018
Document Description

GPROF V05 is the rainfall algorithm used in TRMM V8. It matches in all ways the algorithm from the retrieval for GPM GMI and other satellites in the constellation. The Goddard Profiling Algorithm is a Bayesian approach that nominally uses the GPM Combined algorithm to create it's a-priori databases. Given the importance of these databases to the final product, they are worth reviewing before discussing particular changes to the algorithm. GPROF V03 was implemented at the launch of the GPM mission and thus had no databases from the GPM satellite itself.