Addressing the Polarization Signature of the Ocean Scattering at Ku band in Presence of Both Non-homogenous Winds and Rain

Abstract:

Spaceborne scatterometer observations, especially at Ku-band, are affected by rain and these effects need to be corrected to avoid errors in wind retrievals. Although several semi-empirical techniques have been already developed to correct the wind retrievals, a physical forward model of the backscattering coefficient accounting for both wind and rain may lead to a more accurate approach in estimating winds. Three main steps are needed to construct this model, such as: modeling the effects due to the raindrops impinging over the ocean surface; modeling the attenuation on the signal going through the precipitating event; modeling the volume backscattering introduced by rain. We propose a theoretical model of the ocean surface backscattering coefficient accounting for the surface modifications due to the raindrops’ impact. Modeling both the attenuation and volume backscattering will be the objective of future works. The ocean surface scattering model is based on a modified version of the surface wind waves spectrum developed by Donelan and Pierson (1997) which is suitable to include the splash effects. Main results suggest that this model is able to simulate the co-polar surface backscattering coefficient in both rainy and non-rainy conditions especially at V polarization. However, main discrepancies are found at H polarization where comparisons between the rain-free model and the QuikSCAT Ku-band scatterometer geophysical model function show disagreements especially at medium and high winds. To address this problem we are investigating the model of ocean surface response by analyzing its behavior for different wind wave spectra as well as by comparing it to different geophysical model functions. Moreover, analysis of wind variability will be carried out in order to perform a sensitivity study to the wind changes. Such approach is intended to develop a more realistic model to accurately simulate the ocean surface response considering both polarizations.