IMERG: Rainfall estimates combining data from all passive-microwave instruments in the GPM Constellation (GPM IMERG L3)

GPM Mission Concept

The Global Precipitation Measurement (GPM) mission is an international network of satellites that provide the next-generation global observations of rain and snow. Building upon the success of the Tropical Rainfall Measuring Mission (TRMM), the GPM concept centers on the deployment of a “Core” satellite carrying an advanced radar / radiometer system to measure precipitation from space and serve as a reference standard to unify precipitation measurements from a constellation of research and operational satellites. Through improved measurements of precipitation globally, the GPM mission will help to advance our understanding of Earth's water and energy cycle, improve forecasting of extreme events that cause natural hazards and disasters, and extend current capabilities in using accurate and timely information of precipitation to directly benefit society. GPM, initiated by NASA and the Japan Aerospace Exploration Agency (JAXA) as a global successor to TRMM, comprises a consortium of international space agencies, including the Centre National d’Études Spatiales (CNES), the Indian Space Research Organization (ISRO), the National Oceanic and Atmospheric Administration (NOAA), the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), and others.

For more information on the GPM mission:


This algorithm is intended to intercalibrate, merge, and interpolate “all” satellite microwave precipitation estimates, together with microwave-calibrated infrared (IR) satellite estimates, precipitation gauge analyses, and potentially other precipitation estimators at fine time and space scales for the TRMM and GPM eras over the entire globe. The system is run several times for each observation time, first giving a quick estimate and successively providing better estimates as more data arrive. The final step uses monthly gauge data to create research-level products.

precipitation (mm/hr)
random error (mm/hr)
gauge relative weighting (percent)
probability liquid precipitation (percent)
Zonal Global by 0.1 deg
Meridional Global by 0.1 deg
Temporal Mar 12, 2014 to Jan 2016 by 1 month(s)
Static? no
Volume 75 MB/month
Server public:
Acquired Apr 13, 2015 (Updated Jul 2016)
APDRC contact
Supplements IMERG Technical Documentation
IMERG Algorithm Theoretical Basis Document (ATBD)