Strong wind observations in the atmospheric surface layer

Abstract

The content of this article is a contribution to the limited amount of available strong-wind multi-level tower observations in the atmospheric surface layer, and is primarily intended for those engineers and scientists engaged in the field of wind engineering. The observations were used to evaluate the correctness of the predictions obtained from theoretical and empirical models, the latter used frequently by the wind engineering community. The comparisons included profiles of mean wind, turbulence intensity, and gust velocities. To test the mean-velocity models for the prediction of wind speeds at locations where no recording stations were present, observations at a reference location were used to predict and to compare with the simultaneous observations at a number of locations where wind speed observations were available. The analysis of the data revealed that under strong wind conditions thermal stability effects should not be ignored. For obstacle-free open terrain significant variations of the aerodynamic roughness length are observed. The height of the surface layer that increases with roughness and wind speed is at least 150 m. Davenport's “gradient” height, not a function of wind speed, is approximately twice the height of the surface layer that applies to the strong wind data analyzed. Estimation of wind speed at locations where normally no observations are available may exceed the actual speed by as much as 50%.