COMPARISON OF WAVE BREAKING STATISTICS USING UNDERWATER NOISE AND SEA-SURFACE PHOTOGRAPHIC ANALYSIS CONDUCTED UNDER MODERATE WIND-SPEED CONDITIONS DURING THE SOFIA ASTEX EXPERIMENT

During the Surface of the Ocean, Fluxes and Interactions with the Atmo sphere/Atlantic Stratocumulus Transition (SOFIA/ASTEX) experiment, dev oted to air/sea interactions in the Azores region, a drifting omnidire ctional hydrophone was used in combination with a magnetic photographi c system to validate properties of the ocean surface. Apart from the f act that the noise levels are in good agreement with the Knudsen spect rum, we found, using an underwater sound model, that: the mean spacing between breakers ranges between 50 m and 40 m for mean horizontal win d speeds of 3-9 m/s; and the characteristic surface of whitecaps incre ases more rapidly with the wind speed than the density of whitecaps. T he last result is conjectured to be related to the wind speed range (3 -9 m/s) over which a transition from micro-breaking to spilling (or pl unging) wave breaking is observed.