Lower-atmosphere upper-ocean interactions: the influences of breaking waves

Abstract

Wave breaking at the ocean surface is an important process for air-sea exchange. Whitecaps are visual sea surface signatures of breaking waves. By measuring the fractional coverage of whitecaps on the sea surface, it is possible to quantify wave breaking. This thesis comprises of three distinctive pieces of research. I compare model simulations of sea surface temperature to high resolution observations for three unique cases. The model runs over a daily cycle using a 1-dimensional 2nd moment closure turbulence scheme with the inclusion of a wave breaking model. The comparisons reveal poor performance when the wave breaking model is included. Subsequently, attempts to improve on our understanding of wave breaking were made. I developed a technique for estimating whitecap coverage estimates of both actively breaking (stage A) waves, and maturing (stage B) foam. The Spatial Separation of Whitecap Pixels (SSWP) allows for accurate distinguishing of stage A and stage B whitecap regions by manually evaluating the pixel intensity, location (with respect to the crest of the wave), texture and shape of a given whitecap region. Finally, measured WA and overall whitecap coverage (WT = WA +WB) for the North Atlantic dataset were then compared with modeled estimates of whitecap coverage, derived using a semi empirical formula and various wave-field model parameters. High resolution model estimates of the wave-field are provided by the European Center for Medium Range Weather Forecasting (ECMWF) Wave Model (WAM). Results reveal good performance between WA and modeled generated WT for specific tuning values, which are provided.