Calibration/validation of the SeaWinds radiometer rain rate algorithm

The SeaWinds scatterometer, which has been flown on both the QuikSCAT and ADEOS-II satellites was designed to remotely sense ocean surface wind vectors. Because ocean wind retrievals are occasionally contaminated by rain in the tropics and because there is no independent rain measurement on QuikSCAT, a SeaWinds rain-estimation method was developed and implemented. This technique utilizes the SeaWinds receiver noise to measure ocean radiometric brightness temperature (T_b) and then applies a statistical regression algorithm to estimate the integrated rain rate. This rain algorithm was originally "trained" with QuikSCAT SeaWinds T_b and near-simultaneous rain rate measurements from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). In this study, the SeaWinds instrument on ADEOS-II and the Advanced Microwave Scanning Radiometer (AMSR), also onboard ADEOS-II, were used to refine the algorithm. This provided truly simultaneous and collocated measurements from the same platform and over the same swath, which was ideal for improving the SeaWinds rain algorithm. The improved algorithm can now be applied on QuikSCAT using the SeaWinds radiometric measurement.