THE FEASIBILITY OF USING A HOT-FILM ANEMOMETER IN THE RAIN

Cylindrical, platinum-coated, hot-film anemometers were struck with a series of individual drops of water while immersed in controlled airfl ows with velocities ranging from 0.3 to 5.0 m s(-1). Subjecting the se nsor to water drops caused slight, but permanent, changes in calibrati on. In an effort to overcome calibration changes. following drop impac ts, a Teflon-coated sensor was also tested. A filtering algorithm was devised to remove drop-caused spikes in the recorded time series. An a verage spike duration of 0.32 s per drop impact was found, and maximum record loss was estimated to be 1.7% for rainfall rates less than 30 mm h(-1).