|Coverage||Global Ocean (60N-60S, 0-360E)|
|Time Period||January 1979 - July 1997|
|Resolution||2.5 x 2.5 degree, monthly|
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 size 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.
There is only one version of this dataset and no additional updates are planned.
The Microwave Sounding Unit (MSU) precipitation dataset is an emission-based oceanic retrieval developed by Spencer . The technique calculates the anomalous temperature increase in MSU channel 1 (50.3 GHz), which is primarily due to liquid water emission. This emission signal is then calibrated to a rainfall estimate using rain gauge observations from over 100 coastal and atoll sites around the globe. This dataset is used in the CMAP merged rainfall product.
This dataset is available through NOAA's Climate Diagnostics Center