Laser discrimination between rain and snow

TitleLaser discrimination between rain and snow
Publication TypeConference Proceedings
Year of Conference1984
AuthorsStrachan, J. W., McGurk B. J., and Berg N. H.
Conference Name52nd Annual Western Snow Conference
Series TitleProceedings of the 52nd Annual Western Snow Conference
Date PublishedApril 1984
PublisherWestern Snow Conference
Conference LocationSun Valley, Idaho
KeywordsLaser, Precipitation gage, Remote sensing

In mountainous environments where rainfall or mixed rain and snow comprise significant portions of the winter precipitation, warm-storm and rain-induced peak streamflow discharges can cause flooding and reduce the efficiency of reservoir operations. Most snow accumulation and melt and streamflow forecasting models use air temperature-based procedures to differentiate between rain and snowfall. The precipitation type-air temperature relationship is not completely deterministic and the scarcity of meteorological stations in mountainous areas often necessitates assumptions on temperature change with elevation. A prototype rain-snowfall discriminator is described. The laser/photo-detector unit monitors the fall velocity and indexes the shape of particles passing vertically through a 3-meter horizontal beam. In a laboratory environment the device discriminates between drop former 'rainfall'' and two types of small paper punches. Future research needs include the development and evaluation of a probabalistic algorithm for distinguishing between the three precipitate types, a low power light-emitting diode laser, precipitates more closely resembling snow, and a field prototype gauge.