James Rennell Centre for Ocean Circulation INTERNAL DOCUMENT No. 3 Wind stress and its dependence on wind speed and sea state

The aim of the project is to detect and quantify the egect of sea state on the wind stress. An overview of the basic theory of wind stress in the surface layer is provided, along with a more detailed description of the inertial dissipation method which is used to obtain stress estimates for this study. Wind stress measurements by other researchers illustrate the large scatter which seems to be inherent in the drag coefBcient/wind speed relationship, and parameterisations of the wave Seld have been suggested to explain at least some of this scatter, Past appraisals of the dissipation technique show it to be capable of measuring wind stress over the oceans. Details are given of the data collection and processing to date. The analysis of the data has so far resulted in an lOS report on the performance of a prototype sonic anemometer, and a paper presenting preliminary results at the 1991 lUGG. Drag coefGcients from an early data set are higher than expected and possible reasons for this are discussed. The next stages of data analysis are discussed, and ways of achieving our overall aim of detecting the eSect of sea state on wind stress are described.