On the problem of the near ocean surface wind speed retrieval by radar altimeter: a two-parameter algorithm
In this paper we present results from a theoretical investigation of the scattering of microwave radar signal by the ocean surface. The aim of the research is to generate an improved altimeter wind speed retrieval algorithm, and to achieve this a new theoretical approach to the problem of microwave scattering has been developed. The inadequacy of the assumption of a single valued relationship between surface wind speed and microwave radar backscatter is discussed, and a more complex approach adopted taking into account the nature of the sea surface. Two versions of a two-parameter algorithm (NA1 and NA2) for near surface wind speed retrieval are developed and presented in a tabular form. Co-located altimeter and buoy data are used to test this new algorithm. Good agreement is found between measured and retrieved values with the new algorithms: NA1- the mean difference M=-0.03 m s-1 and rms=1.47 m s-1; NA2- M=0.03 m s-1, rms=1.54 m s-1. Note, that the currently used algorithm WC91 (see below) has the following characteristics: M=0.43 m s-1 and rms=1.69 m s-1. The importance of taking into account the regional specific conditions is emphasized.