A fractal approach to document the Wave-Influenced Boundary Layer in the Large Air-Sea Interaction Facility of Luminy, Marseille

The study of the relationship between wind speed, altitude, and the geometric properties of the ocean surface (characteristics of dominant waves, surface roughness, see the wave-breaking rate) is a central topic both (1) for the representation of the transfer of momentum at the ocean-atmosphere interface in weather, ocean, wave growth forecasting models, and in coupled models, from sub-meso-scale to climate and paleoclimatic scales, and (2) for spaceborne remote sensing of the wind speed at the surface of the oceans, either in microwaves (mainly scatterometers and radiometers) or in visible wavelengths (observation of foam lines). Our study is focused on the surface air layer that is directly influenced by the presence of waves, which is so-called Wave-influenced Bounday Layer (WBL). After a survey of the existing relations found between wind, momentum, and the surface geometry in gradually increasing wind conditions, we will attempt to relate the results of ongoing fractal analyses based on (1) wind field deduced from PIV technique, (2) horizontal wave slope images from light refraction technique, and (3) Laser slice, in a controlled environment.