Hot-Film Measurements from a Small Buoy: Surface Wind Stress Estimates Using the Inertial Dissipation Method

Abstract

The design and deployment of an experimental meteorological buoy are described. A hot-film anemometer is used for in situ calculations of wind velocity variance spectra. The dissipation method is used to derive surface wind stress from the spectra. This is believed to be the first time a hot-film has been installed on a buoy and used to estimate surface wind stress. Buoy-based hot-film measurements provide distinct advantages over shipboard measurements in that they are much less subject to flow distortion by superstructure. The dissipation technique is also less subject to error due to uncertainties in stability-dependent physical mechanisms because the measurements are made very close to the water surface. Results are interpreted in terms of neutral drag coefficients, and simultaneous buoy and shipboard values show less scatter in the buoy data for a 40-h period. Given the variability in the wind speed and direction created by synoptic weather systems, both platforms compare satisfactorily with wind speed parameterizations of the neutral drag coefficient formulated by other investigators. The buoy hot-film data has an apparent wind speed limit of 11 m s?1 due to aerosol impaction. It is believed that this limit can be surpassed by using a sonic anemometer in place of the hot-film sensor.