Wind Fields from SAR in Coastal Areas

Coastal areas (~ within 10 km to 15 km or so from coast), are not covered by any kind of satellite wind data as satellite scatterometer. Due to the interaction between the wind flow and the orography, the wind fields in coastal areas are often not well reproduced both by the atmospheric models, and the possibility to get the wind field from SAR images is here extremely important. Necessary conditions to estimate the wind field from SAR is the knowledge of the wind direction and availability of a reliable ?0-wind speed algorithm. For Cosmo-SkyMed, while the wind direction may be estimated directly from the SAR images, the wind speed is still an issue due the lacking of a tested ?0-wind speed algorithm. This presentation shows how the wind directions may be inferred and highlights the importance of their determination in a geophysical framework. To estimate the wind field from SAR, we refined the 2D continuous wavelet (2D-CWT) technique described in Zecchetto et al, 2002, 2008. SAR-derived wind directions have been against in-situ and regional atmospheric model (Weather Research and Forecasting, WRF). The analysis of the wind directions has shown that the model variability is limited if compared to that SAR, which mostly respects the variability evidenced by in-situ data. The spatial variability of the SAR and model wind 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. The SAR images have been obtained in the framework of the COSMO-SkyMed/RADARSAT-2 Initiative of the Italian Space Agency (ASI) and the Canadian Space Agency (CSA) (Ocean wind fields from C and X-band SAR in the coastal areas, Proposal id 2868/5224). oastal areas (~ within 10 km to 15 km or so from coast), are not covered by any kind of satellite wind data as satellite scatterometer. Due to the interaction between the wind flow and the orography, the wind fields in coastal areas are often not well reproduced both by the atmospheric models, and the possibility to get the wind field from SAR images is here extremely important. Necessary conditions to estimate the wind field from SAR is the knowledge of the wind direction and availability of a reliable ?0-wind speed algorithm. For Cosmo-SkyMed, while the wind direction may be estimated directly from the SAR images, the wind speed is still an issue due the lacking of a tested ?0-wind speed algorithm. This presentation shows how the wind directions may be inferred and highlights the importance of their determination in a geophysical framework. To estimate the wind field from SAR, we refined the 2D continuous wavelet (2D-CWT) technique described in Zecchetto et al, 2002, 2008. SAR-derived wind directions have been against in-situ and regional atmospheric model (Weather Research and Forecasting, WRF). The analysis of the wind directions has shown that the model variability is limited if compared to that SAR, which mostly respects the variability evidenced by in-situ data. The spatial variability of the SAR and model wind 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. The SAR images have been obtained in the framework of the COSMO-SkyMed/RADARSAT-2 Initiative of the Italian Space Agency (ASI) and the Canadian Space Agency (CSA) (Ocean wind fields from C and X-band SAR in the coastal areas, Proposal id 2868/5224).