ASCAT Ultrahigh-Resolution Wind Products on Optimized Grids

The accuracy and spatial resolution of ultrahigh-resolution wind products derived from full-resolution ASCAT radar cross-section measurements are determined by the size and shape of the aggregation area. Current high-resolution products (ASCAT-coastal and ASCAT-6.25) are defined on a regular swath grid (size 12.5 and 6.25 km, respectively) and use a circular aggregation area (15 and 7.5 km radius resp.). For ASCAT-6.25, such approach leads to poor radar sampling, causing noise in the retrieved winds, and poor beam overlap, causing geophysical errors. More regular radar sampling and improved beam overlap can be obtained by using a grid that is synchronized with respect to the ASCAT mid-beam full-resolution measurements. This results in a new generation of ASCAT wind products. It is shown that a product on a 5.6 km grid size (on average) with optimized radar sampling compares better to buoys than ASCAT-6.25, but at the cost of an irregular grid and slightly degraded spatial resolution.