Measurements of Atmospheric Turbulence a Few Meters Above the Sea Surface with a Three Component Thrust Anemometer

摘要

An analysis of atmospheric turbulence data obtained a few meters above the sea with a thrust anemometer during neutral to stable conditions indicates the following results. The intensity of turbulent fluctuations of the horizontal wind components, normalized with respect to the friction velocity, is a function of stability; the normalized turbulence intensity of the vertical component is not strongly related to stability and may be approximated by a constant. The drag coefficient is related to a stability parameter defined by the ratio of the air-sea temperature difference to the square of the mean wind speed. Based on a least squares analysis, the quadratic function relating the drag coefficient to the stability parameter approaches a constant at high wind speeds; at low wind speeds the drag coefficient is strongly related to the stability parameter. It is suggested that the vertical flux of momentum may be estimated during stable conditions from measurements of the stability parameter defined above and the turbulent fluctuations of wind speed; the principal advantage of the technique, which makes it suitable for measurements from non-stationary buoy platforms, is its reduced sensitivity to changes in orientation of the instrument axis. (Author)