Intercomparison of wind speeds observed by AMSR and seawinds on ADEOS-II

The ADvanced Earth Observing Satellite-II (ADEOSII) carried two microwave sensors, AMSR (Advanced Microwave Scanning Radiometer) and SeaWinds, which can measure near-surface wind speed over the global oceans. The wind speeds observed by AMSR and SeaWinds were compared with each other in order to assess consistency of the measurements. It is clearly shown that the first version of the AMSR wind (version 1) has systematic bias with reference to SeaWinds. The trend of bias discontinuously changes around wind speed of 5-6 m/s. This systematic bias in the AMSR wind speed is also confirmed by comparison with data from off-shore ocean buoys, while the SeaWinds wind speed agrees well with buoy data and shows no systematic bias. In an intercomparison of wind speed histograms calculated from global 7-months observations, the AMSR wind (version 1) also shows a skewed histogram with reference to those of SeaWinds and ECMWF (European Centre for Medium-range Weather Forecasts) analysis. It is also shown that the systematic bias is significantly reduced in the revised version (version 3) of the AMSR wind product.