Application of wind wave spectrum model in altimeter wind speed retrieval

Based on the specular reflection theory of electromagnetic waves at rough sea surface and the spectral model of wind waves with a wave age factor, the sea surface wind speeds were retrieved from the normalized radar backscatter cross section measured by TOPEX/Poseidon Ku-band altimeter using the mean square slope calculated from the spectral models of the wind waves and the gravity-capillary waves. The study showed that the wave age factor has a significant influence on retrieving altimeter wind speeds. Compared with the empirical algorithms in operational use for altimeter winds retrieval, after considering the effects of wave age factor, both the bias and the root mean square error between wind speeds retrieved by the proposed analytical algorithm and buoy measured wind speeds in Eastern China Sea decrease significantly. The relationship between the wave age and non-dimensional wave height can be used to calculate the wave age factor based on altimeter measured significant wave height and wind speeds. Thus, the algorithm proposed in this study has a comprehensive applicability.