RADAR BACKSCATTER STATISTICS FROM THE SEA-SURFACE - IMPLICATIONS OF SIR-C X-SAR OBSERVATIONS FROM THE NE ATLANTIC/

Multichannel synthetic aperture radar (SAR) observations from the spac eborne imaging radar-C/X-band SAR (SIR-C/X-SAR) experiment in the NE A tlantic (April 1994) are analyzed to test models of both the mean and the distribution of radar backscatter from the sea surface. The data c over incidence angles from about 20 degrees to 40 degrees and wind spe eds from about 5 to 10 m s(-1). Empirical models of the mean fit the d ata well at C band to an accuracy of within 1-2 dB. Discrepancies at L band are a function of incidence angle, and we cannot rule out the po ssibility that they arise from systematic calibration errors. Single-l ook SIR-C/X-SAR data (spatial resolution similar to 7-10 m) fit well t o a K distribution, but multilook data (spatial resolution similar to 25 m) fit better to a lognormal distribution. The observed second mome nts of image intensity can be explained by the modulations of resolved ocean surface waves but only if relatively large hydrodynamic modulat ions, which are generally consistent with those inferred from tower ra dar data, are assumed.