Wave and wind retrieval from SAR images of the ocean

Over the past few years, recognition of the importance of the coastal zone has led to the establishment of international Programmes for monitoring the coastal zone environment and its change. The European programme MARSAIS is part of this effort. One important component of such actions aims to better predict the sea surface wind and wave dynamics in these vulnerable regions where most economic marine activity is taking place. Indeed, ocean surface wind and wave observations serves both oceanographic and meteorological communities and have direct applications for driving ocean circulation models, numerical predictions and short term forecasts, but also for advancing in the physical understanding of the complex interactions that take place at the ocean-atmosphere interface. As now well recognised, satellite data and particularly the weather independent radar remote sensing data present potential advantages and applications to achieve these requirements. Nowadays, sea surface remote sensing techniques are rapidly developing throughout the world and need some kind of assessment. Altimetry and scatterometry are well proven techniques, which result in recognised operational applications. Synthetic Aperture Radar (SAR) Missions have not enjoyed such successes. However numerous space borne radar images of the ocean surface have revealed a wealth of information on different dynamical processes and SAR images of the ocean surface very, often reveal a remarkable range of signatures on the uppermost layers of the sea. These data have resulted in numerous quantitative scientific findings and theoretical advances in upper-layer and lower atmosphere dynamics. In this review, the main different techniques developed to retrieve surface wave and wind information are recalled. Illustrations are given for ENVISAT wave mode products.