Effects of sensor response and moving average filter duration on maximum wind gust measurements

Abstract

The use of wind speed data recorded using different measuring equipment (i.e. anemometers with different response characteristics) and different signal-processing procedures can introduce errors in the characterisation of surface wind speeds. This study aims to assess the effects of a set of various moving average filter durations and turbulence intensities on the recorded maximum gust wind speeds. For this purpose, a series of wind-tunnel experiments was carried out on the widely-used Vaisala WAA151 cup anemometer. The variations of gust and peak factors, and turbulence intensities measured by the cup anemometer as a function of the averaging duration and turbulence intensity are presented. The wind-tunnel results are compared with values computed from a theoretical approach, namely random process and linear system theory, and the results were also validated against values reported in the literature where possible. The results show that the maximum gust wind speeds measured using large averaging durations (e.g. 3 s or 5 ​s) lead to up to 25%–30% negative biases compared to high frequency measurements (e.g. 4 Hz unfiltered gust measurements). This result can strongly impact subsequent meteorological, climatological and wind engineering studies, as different gust definitions have been adopted by National Weather Services and institutions around the world. Lastly, a set of correction factors (i.e. gust factor ratios) have been proposed that allows measurements at a specific gust duration to be converted to equivalent measurements at specified particular gust durations of interest.