The Effect of Averaging Time and Sample Duration on Estimation and Measurement of Maximum Wind Gusts

Gust factors for tropical cyclone, monsoon and thunderstorm winds

“…Brook and Spillane (1968) revisited the effect of varying averaging time and sample duration on wind gust estimation based on an assumed spectral density function, in which the wind gust is restricted to be normally distributed. Mitsuta and Tsukamoto (1989) expanded the knowledge of time correlation and proposed an experimental formula as:…”

Wind‐gust parametrizations at heights relevant for wind energy: a study based on mast observations

“…For example, W73 estimated that the gust factor within 1 h is about 10% larger than that within 10 min close to the surface; also the change in gust duration from 3 s to 1 s increases the gust factor (e.g. Wieringa, 1973;Brook and , 1968). The height dependence of this difference is, however, unknown.…”

“…He found that this ratio is a function of surface roughness. Brook and Spillane (1968) further developed the methodology of Durst (1960) and extended the idea of Deacon (1965) to derive an equation for the ratio of gusts with different time-scales T and t. In this process they introduced a function for the velocity spectrum, which they then used to estimate the variance of the fluctuations. Their results suggest that gusts with 1 s duration are about 10-15% larger than gusts with a duration of 3 s. The effect of the sampling period (T) is smaller: gusts during 1 h are about 1-5% larger than gusts during 10 min if the gust duration is kept constant.…”

“…Following from this definition, any maximum wind speed during a time period from a fraction of a second (10-20 Hz is a typical measurement frequency of fast-response sonic anemometers) up to 10 min can be called a gust (Brook and Spillane, 1968;WMO, 2008;Harper et al, 2010). The typical averaging period T for the mean wind varies from a few minutes in aviation applications (Young and Kristensen, 1992) to an hour or longer for climate studies (WMO, 2008).…”

“…The WMO (2008) recommendation is 3 s for the gust duration t and 10 min for the mean wind averaging period T. Several studies have focused on the effect of different gust durations and averaging period lengths on gusts (Durst, 1960;Deacon, 1965). Statistical approaches have also been proposed to estimate the effect of gust observing practices (Brook and Spillane, 1968;Beljaars, 1987;Kristensen et al, 1991;Wichers Schreur and Geertsema, 2008). Extreme gusts-the gusts that are located in the upper tail in the gust wind-speed distribution-may cause damage to buildings and other structures.…”