semiell1piricalll1odel of the norll1alized radar cross-section of the sea

Multiscale composite models based on the Bragg theOly are widely used to study the U1LlI<,,'l~"~' radar cross-section (NRCS) over the sea sllrface. However, these models are able to correctly reproduce the NRCS in ail configurations and wind wave conditions. have developed a physical model that takes into account, not only the Bragg nisl11, but also the non-Bragg scattering l11echanisl11 associated with wave breaking. single model was built to explain on the same physical basis both the background . of the NRCS and the wave radar Modulation Transfer Function (MTF) at HH VV polarization. The NRCS is assul11ed to be the SUl11 of a Bragg part (two-scale ) and of a non-Bragg part. The description of the sea surface is based on the short wave spectrul11 (wavelength from few l11illimeters to few meters) developed by et al. [1999] and wave breaking statistics proposed by Phillips [1985]. We that non-Bragg scattering is suppOlied by quasi-specular reflection from vely wave breaking pattems and th<1t the overall contribution is proportional to the white coverage of the surface. A comparison of the model NRCS with observatioris is We show that neither pure Bragg nor composite Bragg model is able to duce observed feature of the sea surface NRCS in a wide range of radar frequencies, . speeds, and incidence and azimuth angles. The introduction of the non-Bragg part in . model gives an improved agreement with observations. In Part 2, we extend the model the wave radar MTF problem. INDEX TERl'vfS: 4275 Oceanography: General: Remote sensing electromagnetic processes (0689); 4560 Oceanography: Physical: Surface waves and tides (1255); 4504 :earlography: PhysicaI: Air/sea interactions (0312); 4506 Oceanography: Physical: Capillary waves; ocean surface waves, radar cross-section, short wind waves, wave breaking, Bragg scattering, ragg scattering