Evidence for the effects of swell and unsteady winds on marine wind stress

Over the past four decades much effort has been directed toward determining a parameterization of the sea surface drag coefficient on readily measurab le quantities, such as mean wind speed and atmospheric stability. Although such a parameterization would have obvious operational advantages, the cons iderable scatter present between experiments, or within any one experiment, indicates that it is not easily achievable. One likely candidate for much of the scatter is the underlying wave field. Unfortunately, few campaigns o ver the years have included spectral measurements of the waves. Among those that have, the results are inconclusive. Here data are presented from the Surface Wave Dynamics Experiment and High Resolution Remote Sensing Program campaigns in which 3-m discus buoys were instrumented with K-Gill and sonic anemometers and complete motion packages to measure the direct (eddy correlation) stress and, concurrently, the dir ectional ocean wave spectrum. These data are examined for the effects of sw ell on the drag coefficient. It is found that much of the scatter in the dr ag coefficient can be attributed to geophysical effects, such as the presen ce of swells or nonstationary conditions.