Satellite Passive Microwave Climate Rainfall Products

Window channel observations from passive microwave radiometers have been used to estimate rainfall since the launch of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) in July of 1987. Over radiometrically cold ocean regions, changes in brightness temperature due to the absorption/emission by liquid hydrometeors at frequencies below the 50-60 GHz oxygen absorption band is directly related to rainfall. While this approach doesn't work over radiometrically warm land surfaces, scattering by precipitation sized ice particles at frequencies above the oxygen absorption band can be used to estimate rainfall. Microwave sounding channel data have also been used to estimate rainfall going back to 1979 from the Microwave Sounding Unit (MSU) on board NOAA's TIROS-N polar-orbiting satellite in October of 1978. Although MSU provides a longer data record than SSM/I, poor spatial resolution of the sensor along with limited precipitation information have limited it use primarily to enhance coverage prior to SSM/I in the merged CMAP product.

SSM/I Emission [More information] [Plot Intercomparison]
A SSM/I 19 GHz emission-based retrieval producing monthly rainfall estimates over the global oceans at a 2.5x2.5 degree spatial resolution. This product is one of the component satellite products produced for the GPCP project and covers the period from July 1987 through the present.
SSM/I Scattering [More information] [Plot Intercomparison]
A SSM/I 85 GHz scattering-based retrieval producing monthly rainfall estimates globally over both ocean and land at a spatial resolution of 2.5x2.5 degrees. This product is one of the component satellite products produced for the GPCP project and covers the period from July 1987 through the present.
SSM/I Combined [More information] [Plot Intercomparison]
A combination of the SSM/I 19 GHz emission algorithm and the 85 GHz scattering algorithm. This product is one of the component satellite products produced for the GPCP project and covers the period from July 1987 through the present.
MSU [More information] [Plot Intercomparison]
The Microwave Sounding Unit (MSU) precipitation dataset is an emission-based oceanic retrieval. The technique calculates the anomalous temperature increase in MSU channel 1 (50.3 GHz), which is primarily due to liquid water emission. This dataset is used in the CMAP merged rainfall product.