Retrieval of Wind Velocity Vectors Over the Ocean Surface with Spaceborne Synthetic Aperture Radar: Implementation and Quality Assessment
Wind velocity measurements at 10 meters over the ocean surface represent an important parameter
to study the ocean behavior. Wind vector fields are available from different sources, such as satellite
derived measurements and weather forecast models. Nevertheless, the limited availability in time,
low spatial resolution and poor coverage close to the coasts motivate research on the use of Synthetic
Aperture Radar (SAR) for wind velocity retrieval.
This report presents an description and assessment of a wind velocity algorithm implemented for
C-band (frequency 4–8 GHz) SAR data. Results obtained with the algorithm are compared and validated
with wind velocity estimates from the Global Forecast System (GFS) model and the Advanced
SCATterometer (ASCAT) sensor on-board the MetOp-A satellite. The statistical results show that the
wind velocity retrievals are in very good agreement with the validation data when the wind field is
slowly varying, leading to a bias in the wind speed smaller than 0.5 ms−1 and a root mean square
error (RMSE) smaller than 2 m/s, and a RMSE about 20◦ in the wind direction. For winds with
high variability, the algorithm agrees better with ASCAT measurements than with the GFS model,
provided that sufficient amount of samples are available to perform the comparison.