Estimation of Significant Wave Height of Near-Range Traveling Ocean Waves Using Sentinel-1 SAR Images

摘要

Synthetic aperture radar (SAR) is a valuable tool to observe many oceanographic parameters of the ocean surface. The significant wave height (H-s or SWH), defined as the mean wave height of the highest one-third of waves, can be estimated using indirect relations between SAR-derived and the actual ocean wave spectra. However, multilook SAR imaging of ocean surface waves is highly affected by degraded azimuthal resolution and the random shift of scattered elements as the waves propagate off the SAR range direction. Therefore, the azimuthal displacement is found to be very low when near-range travelling ocean waves with narrow band spectrum are imaged. In this study, an improved algorithm is developed to directly estimate the significant wave height of ocean waves that propagate in the near-range direction using SARSAR imagery. The slope of the NRCS with respect to the radar wave incidence angle is derived from SAR images using an iterative scheme. A total of 69 SAR images from Sentinel-1A and 1B from 2016 to 2017, acquired near Hawaii, and in situ wave data from nearby National Data Buoy Center buoys are used to estimate H-s and validate the improved algorithm. Results show that the algorithm performs well in estimating SWH under low to moderate wind forcing conditions (4-10 ms(-1)). The accuracy of the SWH estimation decreases under high-wind-speed and wind-wave-dominant conditions.