An effective parametrization of gust profiles during severe wind conditions

A simple and effective parameterization for the profile of extreme wind gusts during severe wind conditions is presented. It is shown that the gust profile follows directly from the logarithmic wind profile. Also the uncertainty in the gust estimates can easily be determined from information of the average wind speed at two different heights. One specification of practical importance is that the maximum 3s-gust in a 10 min period at 10 m height is arithmetically equal to the average wind at 140 m. At larger heights the gusts are equal to the average wind speed at an easily determinable height that is a factor α (α > 1) higher. Validation over The Netherlands indicates that this rule applies to heights up to at least 200 m. This outcome is validated both over land and over sea, and is independent of surface roughness. The proposed parameterization reproduces the climatological values of the measured extreme wind gusts. Maximum gusts for individual winter months are better represented than for individual summer months. The mean error in the monthly winter maxima estimates is 5%.