Sensor Synergy of Active and Passive Microwave Instruments for Observations of Marine Surface Winds

An example of sensor synergy of active and passive microwave instruments for observations of marine surface winds is demonstrated using data from the Advanced Earth Observing Satellite-II (ADEOS-II), which carried a Ku-band microwave scatterometer, SeaWinds, and the Advanced Microwave Scanning Radiometer (AMSR). Scalar wind speed observed by AMSR was evaluated by using wind speed observed by SeaWinds. The intercomparison between the AMSR and SeaWinds wind speeds was largely contributed to improvements of the wind retrieval algorithm for AMSR. The latest version of AMSR wind speed agrees well with buoy and SeaWinds data with negligibly small bias and root-mean-squared difference of approximately 1.5 ms. A discontinuous trend in the wind speed, which was discernible in the earlier versions, was much reduced in the latest version. Wind speed bias which depends on the relative wind direction was significantly reduced compared to the previous versions. Rain flag algorithm developed for the SeaWinds wind products was also assessed using rain data derived from AMSR. Global statistical analyses indicated significant improvements of the rain flag algorithm compared to the previous version. Evaluation of wind speed algorithm of ASMR and rain flag algorithm for SeaWinds will contribute not only to improvements of the wind products of AMSR and SeaWinds on ADEOS-II but also to those of AMSR-E on Aqua and SeaWinds on QuikSCAT, which are not accompanied by active and passive microwave sensor, respectively.