Sea wave numerical simulations with COSMO-SkyMed© SAR data

INTRODUCTION In this paper, X-band COSMO-SkyMed© Synthetic Aperture Radar (SAR) data are first experimented as wind field forcing of coastal wind-wave oceanographic modeling for sea-wave numerical simulation. Experiments consist of numerical wave simulations of the SWAN model accomplished with respect to some relevant wave storms recorded in the test area during the winter season of 2010. The wind forcing is provided by X-band COSMO-SkyMed© SAR-based wind field estimations which are properly blended with both buoys wave data and ECMWF model winds to retrieve meaningful wave parameters (e.g. significant wave height, wave directions and periods) as physical descriptors of storm events. The sea wave numerical simulations are properly accomplished in this coastal environment by means of wind field forcing provided by X-band COSMO-SkyMed© SAR-based wind field retrievals. The SAR data set consists of 60 X-band VV-polarized Level 1B Detected Ground Multi-look (DGM) ScanSAR Huge Region mode COSMO-SkyMed© SAR measurements collected in the Southern Tyrrhenian Coastal area on 2010. Sea wave numerical simulations are accomplished through the SWAN model with respect to some relevant wave storms recorded in the considered test area during the winter season of 2010. A blended wind field product is provided as wind forcing of the SWAN model, which consists of X-band COSMO-SkyMed© SAR-based wind field (i.e. wind speed and direction) retrievals and either buoys wave field or ECMWF model data. Within such a framework, the SAR-based wind speed estimation is accomplished by means of the Azimuth cut-off procedure (Chapron et al., 1995; Kerbaol, 1998; Korsbakken et al., 1998; Migliaccio et al., 2012; Montuori et al., 2012), while the SAR-based wind direction retrieval is accomplished by using the Multi-Resolution Analysis of Discrete Wavelet Transform (MRA-DWT) (Du et al., 2002). The output of SWAN model numerical simulations allows providing relevant wave parameters (e.g. significant wave height, wave directions and periods), which are used as physical descriptors of storm events. The experimental results gathered with X-band COSMOSkyMed© SAR-based wind field forcing are compared with the ones provided by using both buoys wave field data and ECMWF model winds, only. The comparison is accomplished to analyze the capabilities of blended wind field products composed by Xband COSMO-SkyMed© SAR wind field estimations and model data in terms of sea wave numerical simulations, in order to be further used for coastal management purposes. The innovative features of the project are the following: 1. With respect to the SAR-based wind field estimation procedures, the proposed approach was the SAR Wind Algorithm (SWA) based on the Azimuth cut-off procedure (Korsbakken et al., 1998; Bruning, et al., 1990; Kerbaol, et al., 1998). This approach, based on the filtering operated by SAR system in the azimuth channel, allows estimating the wind speed over the sea by ABSTRACT