Rapid temporal changes of boundary layer winds

The statistical distribution of the magnitude of the vector wind change over 0.25-, 0.5-, 1-, and 2-h periods based on central Florida data from November 1999 through August 2001 is presented. The distributions of the 2-h u and v wind-component changes are also presented for comparison. The wind changes at altitudes from 500 to 3000 m were measured using the Eastern Range network of five 915-MHz Doppler radar wind profilers. Quality-controlled profiles were produced every 15 min for up to 60 gates, each representing 101 m in altitude over the range from 130 to 6089 m. Five levels, each constituting three consecutive gates, were selected for analysis because of their significance to aerodynamic loads during the space-shuttle-ascent roll maneuver. The distribution of the magnitude of the vector wind change is found to be lognormal, consistent with earlier work in the midtroposphere. The parameters of the distribution vary with time lag, season, and altitude. The component wind changes are symmetrically distributed, with near-zero means, but the kurtosis coefficient is larger than that of a Gaussian distribution.