Spaceborne SAR for Ocean Wave Measurements in Global and Regional Scales

Abstract

In this paper, we presented our collaboration on studies retrieval of ocean wave parameters, i.e., integral wave parameters by spaceborne SAR data, in the global and regional oceans. By using the ENVISAT/ASAR wave mode data acquired in its full life cycle (2002 – 2012) over the global ocean, we developed a dataset consisting of integral ocean wave parameters of significant wave height (SWH) and mean wave period (MWP). Both parameters are calibrated and validated against buoy data. A cross-validation between the ASAR SWH and radar altimeter (RA) data is also performed to ensure that the SAR-derived wave height data are of the same quality as the RA data. These data are stored in the standard NetCDF format, which are produced for each ASAR wave mode Level1B data provided by the European Space Agency. This is for the first time that a full sea state product is derived from spaceborne SAR data over the global ocean for a decadal temporal scale. Using similar algorithm, i.e., parametric model, which relates SAR observed normalized radar cross section (NRCS) and other radar parameters with ocean wave parameters, we further developed Sentinel-1 SAR wave mode data product for global oceans. In regional scale, SAR data acquired in stripmap or ScanSAR modes are used to derive ocean wave parameters. These data have not only high spatial resolution but also relatively large spatial coverages, and therefore are useful for mapping of ocean wave in regional scales. Compared with wave mode data with fixed radar incidence angles, they vary significantly from near to far ranges, particularly for ScanSAR and wide ScanSAR modes. Therefore, by adopting previously developed parametric model, effect of incidence angles is included. The SAR-derived SWH is systematically validated by comparing RA data and buoy measurements and shows a good accuracy.