Atmospheric turbolence

The wind on the sea, usually summarised as an average value over the last ten minutes, is characterised by turbulence (gustiness) acting at different scales, from the micrometric level (order of second) till the synoptic one (tens or minutes or more). The exchanges at the sea surface (energy, momentum, heat, gases, spray) between ocean and atmosphere depend in a nonlinear way (quadratic or higher) on the wind speed. Therefore their correct evaluation requires a detailed knowledge of the turbulent motions in the lower layers of the atmosphere. These motions have been studied for many years on the base of the data recorded at the tower, in particular in relationship to the generation of wind waves (Abdalla and Cavaleri, 2002). The derived physical description is now integral part of the WAM wave model (Komen et al., 1994) used for operational prediction at most of the meteo-oceanographic centres.