Comparisons between the TAO buoy and NASA scatterometer wind vectors

There was an opportunity to compare 10 months of collocated National Aerona utics and Space Administration scatterometer (NSCAT) wind vectors with thos e from the Tropical Atmosphere Ocean (TAO) buoy array, located in the tropi cal Pacific Ocean. Over 5500 data pairs, from nearly 70 buoys, were colloca ted in the calibration/validation effort for NSCAT. These data showed that the wind speeds produced from the NSCAT-1 model function were low by about 7%-8% compared with TAO buoy winds. The revised model function, NSCAT-2, pr oduces wind speeds with a bias of about 1%. The scatterometer directions we re within 20 degrees (rms), meeting accuracy requirements, when compared to TAO data. The mean direction bias between the TAO and the NSCAT vectors (r egardless of model function) is about 9 degrees with the scatterometer wind s to the right of the TAO winds, which may be due to swell. The statistics of the two datasets are discussed, using component biases in lieu of the sp eed bias, which is naturally skewed. Using ocean currents and buoy winds me asured along the equator, it is shown that the scatterometer measures the w ind relative to the moving ocean surface. In addition, a systematic effect of rain on the NSCAT wind retrievals is noted. In all analyses presented he re, winds less than 3 m s(-1) are removed, due to the difficulty in making accurate low wind measurements.