Creating a Multidecadal Ocean Microwave Brightness Dataset: Three-Way Intersatellite Radiometric Calibration Among GMI, TMI, and WindSat

The Tropical Rainfall Measuring Mission (TRMM), launched in late November 1997 into a low earth orbit, produced the longest satellite-derived precipitation time series of 17 years. During the second half of this mission, a collection of cooperative weather satellites, with microwave radiometers, was combined to produce a 6-h tropical precipitation product, and the TRMM Microwave Imager (TMI) was used as the radiometric transfer standard to intercalibrate the constellation members. To continue this valuable precipitation climate data record, the Global Precipitation Mission (GPM) observatory was launched in February 2014, and the GPM Microwave Imager (GMI) became the new transfer standard that normalized the microwave radiance measurements of the GPM constellation radiometers. Previously, the Central Florida Remote Sensing Lab conducted intercomparisons over oceans, between TMI and the Naval Research Laboratory's WindSat polarimetric radiometer and found that the radiometric calibration of TMI relative to WindSat exhibited exceptional long-term radiometric stability over a period >8 years. Moreover, for purposes of assessing global climate change, it is crucial that a seamless transfer between the TRMM and the GPM microwave brightness temperature time series be achieved. Therefore, this paper presents arguments that the 3-way (WindSat, TMI, and GMI) intersatellite radiometric comparisons, performed during the 13-month period overlap, can be used to bridge the TRMM and GPM eras and assure a stable radiometric calibration between the diverse constellation's member radiometers.