Satellite passive microwave sensors have been in operation since the 1970's. These include the Microwave Sounding Unit (MSU); the Special Sensor Microwave/Imager (SSM/I); the Advanced Microwave Sounding Unit (AMSU); the Advanced Microwave Scanning Radiometer (AMSR); the Tropical Rainfall Measurement Mission Microwave Imager (TMI); and the Global Precipitation Mission Microwave Imager (GMI). The AMSU-A and AMSU-B (replaced by the Microwave Humidity Sounder (MHS) on later satellites have been taking detailed moisture and temperature measurements since 1998 and have flown aboard the NOAA-15, -16, -17, -18, -19, and MetOp-A, -B, and -C satellites. These data were originally intended to be used primarily for operational weather prediction. Since there is now a nearly twenty-year record and because there have been multiple satellites operating simultaneously, thus providing increased diurnal coverage, these data may also be useful for hydrological climate studies, and can be used not only as stand-alone time series but also combined with similar measurements from other sensors. In order to do this, the first step is satellite calibration and inter-calibration, thereby generating Fundamental Climate Data Records (FCDRs) of the satellite brightness temperatures (TBs) which have the stability and homogeneity necessary for climate studies.
Thematic Climate Data Records (TCDRs) are generated from these inter-calibrated TBs using the Microwave Surface and Precipitation Products System (MSPPS). The specific products are total precipitable water (TPW), cloud liquid water (CLW), sea-ice concentration (SIC), land surface temperature (LST), land surface emissivity (LSE) - all from AMSU-A and from AMSU-B/MHS - rain rate (RR), snow cover (SC), ice water path (IWP), and finally snow water equivalent (SWE). Inter-satellite analyses of these products are made together with comparisons to similar observed products such as the Global Precipitation Climatology Product (GPCP), the Advanced Microwave Scanning Radiometer 2 (AMSR-2), the Interactive Multisensor Snow and Ice Mapping System (IMS), and model reanalysis products such as the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2), and the Global Forecast System (GFS), all for the period 2002 to 2018, in order to show the strengths and weaknesses of these AMSU-A and AMSU-B TCDR products.