Global ocean wave analysis based on the 10-year ENVISAT/ASAR wave mode data

Abstract

The Synthetic Aperture Radar (SAR) Wave Mode (WM) is an imaging mode dedicated to ocean surface wave observation. Since the first used in the ERS-1/SAR in 1991, this imaging mode has been continuously acquired by ERS-2, ENVISAT/ASAR, Sentinel-1A/1B and the GaoFen-3, and has been providing ocean wave observation data for almost 30 years. As the Envisat/ASAR has the longest archived WM data, we used a parametric model named CWAVE_ENV to retrieve ocean wave parameters of significant wave height (SWH) and mean wave period (MWP) from all the ASAR WM data in its lifetime from December 2002 to April 2012. By comparing with the ECMWF and NDBC buoy data, we found good agreements between the ASAR retrieved results and the buoy measurements. The retrieved ASAR integral wave parameters are further calibrated using the buoy measurements based on the Reduced Majored Axes (RMA) regression method. By calibration, the bias of SWH and MWP are improved from −0.06 m to 0.00 m and from −0.19 s to 0.00 s. Cross-validation of the calibrated ASAR wave parameters with the JASON-1 Radar Altimeter SWH also shows a good consistency, with the correlation coefficient of 0.93, the bias and RMSE of 0.18 m and 0.53 m, respectively. The proposed 10-year global wave product could be a good complementary to the Radar Altimeter product and possible good dataset for wave climate study. A preliminary result of using these data for global wave analysis is shown as well in this paper.