Application of state-of-the-art SAR X-band geophysical model functions (GMFs) for sea surface wind (SSW) speed retrieval to a data set of the Italian satellite mission COSMO-SkyMed

Abstract

The concurrent presence of three satellite X-band SAR systems makes it interesting to test the interoperability of retrieval approaches meant for one system on the others. To approach this problem a description of the state of the art of the SAR X-band geophysical model functions (GMFs) for sea surface wind (SSW) speed retrieval is carried out. A sensitivity study of wind speed retrieval with respect to the wind direction when using the XMOD2 GMFs developed at the German Aerospace Center (DLR) and the Italian Space Agency (ASI) is presented. An application of these two GMFs to a series of data sets of stripmap images with vertical polarization VV acquired by the Italian satellite mission COSMO-SkyMed (CSK) is discussed, and the results of the SSW speed retrieval are compared to both the National Centers for Environmental Prediction (NCEP) blended sea winds and in situ buoy data from the National Data Buoy Center (NDBC). The retrieval exercises show that the two GMFs have similar performance. The sensitivity study shows that an error of ±10°may introduce an error greater that 10% in the retrieval of SSW speed.

Uncertainty Analysis in SAR Sea Surface Wind Speed Retrieval through C-Band Geophysical Model Functions Inversion

“…This yields that the CMOD7 is provided by tabled values of NRCS for a number of specific triplets (θ,W,ϕ). Whatever the exploited GMF, SAR SSW speed W may be estimated from the minimization of a cost function J, defined as follows [42]:…”

“…Ref. [42] presents a sensitivity study of wind speed retrieval with respect to the wind direction when using the X-band model 2 (XMOD2) GMFs developed at either the German Aerospace Center (DLR) or the Italian Space Agency (ASI). The study shows that an error of ± 10 • for the SSW direction may introduce an error greater than 10% in the retrieval of SSW speed.…”

Combining COSMO-SkyMed satellites data and numerical modeling for the dynamic management of artificial recharge basins

“…1), which shield the ARB resulting in calm conditions. The calm and thus smooth water surface has low backscatter, which is less than −13 dB for calm conditions with wind speed < 2 m/s (i.e., below Force 2 in the Beaufort wind scale) at the upwind direction (Grieco et al, 2015) for the incidence angle of 26° (smallest incidence angles among all SAR images; see Table 1S).…”

“…Active microwave sensors, such as synthetic aperture radar (SAR), are very effective tools to detect the presence of water in various landscape conditions including open surfaces, vegetated agricultural lands, and urban areas, regardless of cloud cover and absence of solar illumination (Paloscia et al, 2008;Paloscia and Santi, 2012). Compared to other land surface types, water surface typically has very low radar backscatter, especially at large incidence angles, showing different polarization signatures depending on wind speed and wind direction (Grieco et al, 2015;Li and Lehner, 2014;Nghiem et al, 1997Nghiem et al, , 2004. This important property can be used to identify inland water bodies from other surface targets.…”