On the statistics of the phase of microwave backscatter from the ocean surface

Abstract

In this paper we describe what we believe is the first study of the distribution of the phase of microwave fields backscattered from the ocean surface. Scatterometry data from the Synthetic Aperture Radar and X band Ocean Nonlinearities experiment conducted on the German North Sea Research Platform, Forschungsplatform Nordsee, in November 1990 have been analyzed to reveal the distribution of phase differences as a function of time lag. A theoretical model for these statistics is presented based on modulated Gaussian fields. This theoretical model is shown to be in good agreement with the measured statistics. From this agreement we conclude that the backscattered fields have a Gaussian distribution on short time scales but are modulated in amplitude and frequency by the long surface waves. These results are of more than purely academic interest, with direct applications to the design and analysis of interferometric synthetic aperture radars, a relatively new class of instruments that may be capable of providing high‐resolution maps of ocean surface currents from aircraft or satellites.