THE POLARIZATION-DEPENDENT RELATION BETWEEN RADAR BACKSCATTER FROM THE OCEAN SURFACE AND SURFACE WIND VECTOR AT FREQUENCIES BETWEEN 1 GHZ AND 18 GHZ

ESA's ERS-1 mission includes a C-band VV polarization wind scatterometer for which a wind-field-retrieval algorithm has been developed using a radar signature model CMOD1. A series of airborne scatterometer measurements were carried out in the framework of the EOPP (ESA's Earth Observation Preparatory Program) with the multifrequency airborne scatterometer DUTSCAT (TOSCANE-2 campaign 1987). The objective of this activity is to establish a multifrequency dual-polarization radar signature data base, and with it a multidimensional version of the current CMOD1 model. The main features of the data set are the following. The wind exponent-gamma of the upwind NRCS increases with frequency and incidence angle in the case of HH polarization. This trend is less note-worthy for VV polarization. The upwind/downwind ratio UD is mainly negative at 20-degrees of incidence angle, always at C-, X-, and Ku1-bands. The difference DELTA-UD between HH and VV polarization is increasing with the incidence angle, except at L-band. The upwind/crosswind ratio UC increases with the incidence angle and varies very little with the polarization.