SIMULATING THE INFLUENCE OF WAVE WHITECAPS ON SAR IMAGERY

This work provides a new application of numerical pseudo-random simulation of satellite active sensor imagery ([1] and [2]), which allows a greater freedom to introduce complex hydrodynamic mechanisms compared to the traditional spectral analytical procedure. After previous works [3] and [4] on the basic methodology, which mainly concentrated on tilting and Doppler shift effects, the possibility is examined here of including the effects of wave whitecapping in the simulation. Recent results as in [5] and [6] highlight the importance of wave breaking and the consequent formation of whitecaps on the image formation mechanism. Such an effect was already considered in [7] and [8] in connection with passive microwave sensors; it was also taken into account as a possible element of SAR sea current visualization by [5], [6] and [9], but it is still relatively new within the context of SAR wind and wave analysis, which until recently was assumed to depend mainly on capillary wave modulation and tilt. On the other hand, in the last few years the understanding of offshore wave breaking and whitecap formation has improved to the point that such processes can be confidently included in the image modeling. Some examples are given on how to represent whitecapping in the simulation, also by including the effects of the Doppler shift and its role in generating the final SAR image. Results from [10] and [11] are used to identify the generation of whitecaps through an appropriate parameter, together with up to date formulas for the determination of whitecap covered sea surface fraction as exposed in [12] and [13]. Numerical spectral SAR images are simulated in previous works [3] and [4]