On the parameterization of drag coefficient over sea surface

Six parameterization schemes of roughness or drag coefficient are evaluated on the basis of the data from six experiments. They present great consistency with measurement when friction velocity u(*)<0.5 m/s (approximately corresponding to 10 m wind speed U-10<12 m/s) and large deviation from measurement when u(*)>= 0.5 m/s (approximately U-10 >= 12 m/s). In order to improve the deviation, a new parameterization of drag coefficient is derived on the basis of the similarity theory, Charnock relationship and Toba 3/2 power law. Wave steepness and wind-sea Reynolds number are considered in the new parameterization. Then it is tested on the basis of the measurements and shows significant improvement when u(*) >= 0.5 m/s. Its standard errors are much smaller than the ones of the other six parameterizations. However, the new parameterization still needs more tests especially for high winds.