WIND FLUCTUATIONS NEAR THE GROUND DURING RAIN

Measurements of wind speed were made above short grass during periods of rainfall using hot-film anemometers. A filtering algorithm was used to identify spikes in the anemometer signal time series, induced by r aindrop impacts on the hot-film sensors. A relatively small number of such spikes, comprising about 0.1-0.2% of the data points, were identi fied in signals recorded during rainfall with rates ranging from less than 0.1 to 7.2 mm h(-1). After these spikes were removed from the tim e series by filtering, the resulting values of the first four moments of wind speed were very similar to those found above grass during fair weather. Values of sigma(w)/u and sigma(u)/u* determined during rain using a 3-D sonic anemometer(l.3 and 2.6, respectively) were also in good agreement with corresponding values found during conditions of fa ir weather and near-neutral atmospheric stability.