Evaluation of marine surface winds observed by active and passive microwave sensors on ADEOS-II

Marine surface winds observed by two microwave sensors, SeaWinds and Advanced Microwave Scanning Radiometer (AMSR), on the Advanced Earth Observing Satellite-II (ADEOS-II) are evaluated by comparison with off-shore moored buoy observations. The wind speed and direction observed by SeaWinds are in good agreement with buoy data with root-mean-squared (rms) differences of approximately 1 m s^-1 and 20°, respectively. No systematic biases depending on wind speed or cross-track wind vector cell location are discernible. The effects of oceanographic and atmospheric environments on the scatterometry are negligible. Though the wind speed observed by AMSR also exhibited reasonable agreement with the buoy data in general with rms difference of 1.3 m s^-1 it is systematically lower than the buoy data for wind speeds lower than 5 m s^-1. Similar results are obtained in an intercomparison of wind speeds globally observed by SeaWinds and AMSR on the same orbits. Global wind speed histograms of the SeaWinds data and European Centre for Medium-range Weather Forecasts (ECMWF) analyses agree precisely with each other, while that of the AMSR wind shows slight deviation from them.