Variation of Lateral Gustiness with Wind Speed

The variations of lateral gustiness with wind speed were studied using a light-weight, fast-response wind system coupled to an automatic sampling system. Accuracies of 1° in determining the width of the wind direction distribution and 1 km hr−1 in determining wind speeds above the 1 km hr−1 threshold were obtained. Results show a decreasing trend of lateral direction fluctuations with increasing wind speed, for speeds >2 m sec−1. For winds <2 m sec−1, direction fluctuations increase with increasing wind speed, both during stable and unstable conditions. It is suggested that increasing wind speed is necessary to provide the energy to overcome pressure resistance to lateral fluctuations, which therefore increase with wind speed. This result is consistent with continuity considerations. At higher wind speeds, increasing air momentum results in a decrease of fluctuations with increasing wind speed. The product of wind speed and the width of the lateral fluctuation distribution increases monotonically for all wind speeds, which agrees with present experimental evidence.