WAVE-INDUCED WINDS FOR SHOALING WAVES: A LABORATORY STUDY

Air-sea fluxes of heat, gases, momentum is dominated by the interaction between air and water at the interface (Donelan, Csanady, 2001). It is intuitive that wind generates wave by exerting a stress on the surface. Several researchers focused on the energy and momentum transfer at the air-sea interface by parametrizing a drag coefficient to express wind-generated waves in terms of a single velocity in air (usually the air friction velocity u* or the 10-m velocity U10) (Sullivan and McWilliams, 2010). Many coupled ocean-atmosphere models rely on such parametrization for weather forecasting (Cavaleri et al, 2007), which often imply that wind velocity is higher than the wave phase speed. However, less attention has been devoted to swell propagating faster than the reference wind speed, which in the real world can appear both offshore and nearshore. In that case, the wave field generates (wave-induced) winds, and transfers momentum and energy to the atmosphere. Recent studies showed that the current models used for coupled models are not adequate to describe this phenomenon, yielding to misleading forecasting (Smemdan 1999, CBLAST-Low, Yun and French 2016, Aird et al. 2022). Here, we present a laboratory study of a monochromatic wave propagating on a mild-slope bottom, in conditions of no wind. Our aim is to observe how different wave frequencies and water depths influence the air flow above.