Wind Fields From C- and X-Band SAR Images at VV Polarization in Coastal
Area (Gulf of Oristano, Italy)
Abstract
This work deals with the spatial characteristics of the wind fields
evaluated from synthetic aperture radar (SAR) images and simulated by
the weather research and forecasting (WRF) atmospheric model in the
Gulf of Oristano, a small coastal area about 10 km × 18 km wide in
western coast of Sardinia (Western Mediterranean Sea). The SAR-derived
wind fields have been obtained analyzing images of the COSMO-SkyMed,
Radarsat-2, and Sentinel-1A satellites through a fully two-dimensional
continuous wavelet transform (2-D-CWT) method. The analysis of the wind
directions has shown that the model variability is limited if compared
to that inferred by 2-D-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 assessed: 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 scales. 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.