Wind Fields from C and X band SAR images at VV polarization in coastal area

This work shows and discusses the spatial characteristics of the wind fields evaluated from SAR and atmospheric model in the Gulf of Oristano, western coast of the Sardinia (Western Mediterranean Sea), a small basin about 10 km by 18 km wide. The SAR derived wind fields have been obtained from the images of the COSMO-SkyMed, Radarsat-2 and Sentinel-1A satellites through a fully two-dimensional continuous wavelet method (2D-CWT), and the model winds from the Weather Research and Forecasting (WRF) model. The analysis of the wind directions has shown that the model variability is limited if compared with that inferred by 2D-CWT method, which mostly respects the variability evidenced by in-situ data. As the use of model directions to compute the SAR wind fields is a standard in many studies, the impact on the SAR wind speed retrieval of using the model instead of the SAR derived directions has been reported: differences of wind speed greater than ±10% occur for about the 20% of data. The spatial variability of the SAR and model wind speed fields results quite different at both local and domain scale. The knowledge of the spatial variations of the surface wind fields can be very important for the oceanographic applications and constitutes the added value brought by SAR in the description of the coastal wind. For this reason the SAR derived wind fields should be taken as reference in many kind of applications.