Analysis and Validation of High-Resolution Wind From ASCAT

The standard ocean wind product from the Advanced Scatterometer (ASCAT) is retrieved on a 12.5-km grid. Ultrahigh-resolution (UHR) processing enables ASCAT wind retrieval on a high-resolution 1.25-km grid. Ideally, such a high-resolution grid allows for improved analysis of winds with high spatial variability, such as those in near-coastal regions and storms. This paper provides an analysis and validation of ASCAT UHR wind estimates to evaluate its spatial resolution and accuracy. This is done via a comparison with two other sources: buoy-measured winds in coastal regions and winds estimated from synthetic aperture radar (SAR) data over the open ocean. Near-coastal ocean measurements may be contaminated by nearby land, introducing a wind speed bias in the retrieved winds. To enable near-coastal UHR wind retrieval, we use a land contribution ratio (LCR) approach to discard ASCAT measurements with high land contamination before UHR processing and wind retrieval. Through a comparison with near-coastal buoy winds, we find that the LCR approach is appropriate for precisely controlling the tradeoff between land contamination and spatial coverage near land. We find that the resolution of the UHR data is improved over the 25-km wind product to 10 km, and likely down to 4 km in some cases. In comparing SAR and UHR winds, we find that both products have common fine-scale features and have derivative fields that match well and that the UHR product matches better the expected spectral properties of ocean winds.