ACCOUNTING FOR SURFACE-WAVE DISTORTION OF THE MARINE WIND-PROFILE IN LOW-LEVEL OCEAN STORMS WIND MEASUREMENTS

Marine wind measurement at three heights (3.0, 4.5, and 5.0 m) from bo th moored and drifting buoys during the Ocean Storms Experiment are de scribed. These winds are compared with each other, with winds from shi ps, from subsurface ambient acoustic noise, and from the analyses of t hree numerical weather prediction centers. In the mean, wind direction s generally differ by only a small constant offset of a few degrees. N o wave influence on the wind direction is evident, because the differe nces are not systematic and with few exceptions, they are less than th e expected error. After correcting for some apparent calibration and i nstrument bias, the Ocean Storms wind speeds display similar behavior when compared to the analyzed wind products. There is excellent agreem ent up to a transition wind speed between 7 and 10 m s(-1), above whic h all me measured winds tend to be relatively low. The transition spee d is found to increase with anemometer height, so this behavior is int erpreted as being due to the distortion of the wind profile by surface waves. The wave effects are shown to be profound. By increasing the s tress by 40% or more in high winds, the corrections are shown to be es sential for numerical models to simulate the oceanic response to storm events. The Ocean Storms corrections are used to construct functions describing wave influence on both the vertical wind shear and the mean wind speed profile. These functions can only be regarded as crude app roximations because the Ocean Storms data are far from ideal for deter mining them. However, they can be used to assess potential influences of surface waves on any low-level wind measurement.