SeaWinds Validation: Effect of Rain as Observed by East Coast Radars

Abstract

To examine the accuracy of the SeaWinds scatterometer wind data and rain flags, and how this accuracy depends on ground-based radar-estimated rain rate, SeaWinds data, WSI NEXRAD precipitation rates, and selected Eta analysis variables are collocated. [SeaWinds is the NASA scatterometer on the QuikSCAT and Advanced Earth Observing Satellite (ADEOS)-2 satellites, WSI NEXRAD precipitation data are from a Weather Services International Corporation product based on the U.S. Next Generation Radar (NEXRAD) network of Weather Surveillance Radar-1988 Doppler (WSR-88D) installations, and Eta is the NCEP operational mesoscale model.] Only data close to the east coast of the United States are collected, where both the WSI NEXRAD data and the Eta analyses are accurate. For the subset of data for which WSI NEXRAD detects no rain, within the optimal part of the swath, and for Eta analysis wind speeds between 3 and 20 m s?1, the rms differences between SeaWinds and Eta analysis wind speed and direction are 1.73 m s?1 and 21°, respectively. These rms differences increase significantly whenever WSI NEXRAD detects rain, even light rain. The SeaWinds rain indices are strongly correlated with the WSI NEXRAD precipitation rates. While for high rain rates most winds are correctly flagged, many cases of light rain are not detected.