Study of Sensitivity in Wind Direction Retrieval From Sentinel-1 Images

Retrieval of sea wind vector from Synthetic Aperture Radar (SAR) data is one of the most widely used methods, since it can give high wind resolution cell. For this approach, wind direction is normally the first retrieved parameter, since it plays a crucial role in many inversion models (CMOD, XMOD) to estimate wind speed. In spite of the huge studies of wind field retrieval, little has been reported about the sensitivity of wind direction retrieval at different scales, especially at a wind resolution cell of 1 km x 1 km. This is particularly significant for C-band Sentinel-1 images which have generally high spatial resolutions. In order to investigate this issue, the Local Gradient method is selected to retrieve wind directions from the Sentinel-1 data at different scales, with regard to the spatial resolution (or acquisition mode) of SAR images, speckle noise, and wind regimes.