The MIRS GPM precipitation retrieval

The Microwave Integrated Retrieval System (MIRS) is an operational system at National Oceanic and Atmospheric Administration (NOAA) providing satellite derived information since 2007. The system has been extended to retrieve variables based on the Global Precipitation Measurement Microwave Imager (GPM/GMI) instrument observed radiances. The inversion algorithm is a One-Dimensional Variational (1DVAR) scheme and is consistent across sensors and uses an iterative approach in which a solution is sought that best fits the observed satellite radiances, subject to other constraints. The Community Radiative Transfer Model (CRTM) is used as the forward and Jacobian operator to simulate the radiances at each iteration prior to fitting the measurements to within the noise level. This paper describes the MiRS retrieval algorithm, its extension to GPM/GMI, and validation against several reference data sets, including National Centers for Environmental Prediction (NCEP) Stage IV precipitation analyses, as well as with the European Centre for Medium-Range Weather Forecasts (ECMWF). Results indicate that MiRS can retrieve details of the atmospheric water vapor, hydrometeors and surface precipitation in an accurate and self-consistent manner.