The Response of the Dines Anemometer to Gusts and Comparisons with Cup Anemometers

Abstract

he Dines pressure tube anemometer was the primary wind speed recording instrument used in Australia until it was replaced by Synchrotac cup anemometers in the 1990s. Simultaneous observations of the gust wind speeds recorded using both types of anemometers during tropical cyclones have, however, raised questions about the equivalency of the gust wind speeds recorded using the two instruments. An experimental study of the response of both versions of the Dines anemometer used in Australia shows that the response of the anemometer is dominated by the motion of the float manometer used to record the wind speed. The amplitude response function shows the presence of two resonant peaks, with the amplitude and frequency of the peaks depending on the instrument version and the mean wind speed. Comparison of the gust wind speeds recorded using Dines and Synchrotac anemometers using random process and linear system theory shows that, on average, the low-speed Dines anemometer records values 2%?5% higher than those recorded using a Synchrotac anemometer under the same conditions, while the high-speed Dines anemometer records values 3%?7% higher, depending on the mean wind speed and turbulence intensity. These differences are exacerbated with the adoption of the WMO-recommended 3-s moving average gust wind speed when reporting the Synchrotac anemometer gust wind speeds, rising to 6%?12% and 11%?19% for low- and high-speed Dines anemometers, respectively. These results are consistent with both field observations and an independent extreme value analysis of simultaneously observed gust wind speeds at seven sites in northern Australia.