Validation of QuikSCAT wind vectors by dropwindsonde data from DOTSTAR

The accuracy of 10-meter wind vectors derived from the QuikSCAT satellite near tropical cyclones is validated against soundings from 457 GPS dropwindsondes deployed by DOTSTAR (Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region) during 2003-2007. To maximize the database, the surface to 40-m wind speed in the dropwindsondes is averaged and interpolated to the 10-m wind speed by linear regression. After removing rain-flagged data, the root-mean-squared differences between QuikSCAT and dropwindsonde data were 2.6 m s-1 or 18% (wind speed) and 17¢ª (wind direction) based on 896 matching samples. Further analyses also indicate that the QuikSCAT data slightly underestimates the wind speed of medium wind regime (between 10 and 17.2 m s-1) and possesses some clockwise directional bias in the high wind regime (above 17.2 m s-1). In summary, this study suggests that the QuikSCAT wind vectors below tropical storm wind strength (17.2 m s-1) are accurate enough for forecasters to determine the critical wind radius of 34-kt wind, while a new error bound of the QuikSCAT wind estimate in high-wind regimes near tropical cyclones is suggested to be set at about 4 m s-1.