Window channel measurements from the NOAA-15 Advanced Microwave Sounding Un
it (AMSU) are used to retrieve rain rates. This study focuses on the rain r
ate retrievals over land and uses measurements at 89 and 150 GHz to detect
a scattering signal by millimeter-sized ice particles under precipitating a
tmospheres. An operational algorithm using the AMSU-A module (89 GHz) imple
mented in August 1999 is also described. The algorithms are calibrated with
hourly surface rain observations. It is shown that identification of strat
iform rain can be dramatically improved using measurements at 150 GHz from
the AMSU-B sensor. Improved spatial resolution of AMSU-B is a major factor
contributing to this algorithm.