Analysis of Winter Precipitation Observations in the Cooperative Snow Investigations

In the Cooperative Snow Investigations of the Corps of Engineers and Weather Bureau, observations were made of precipitation measurements in different kinds of gages and of water equivalent of snow on the ground at a great variety of station sites in the mountains of California and Montana for the five winter seasons ending 1950–51. Much of the variation in catch of precipitation over rugged areas of 4 to 20 square miles is ascribed to variations in local exposure and in natural sheltering of the gages. Wind speed appears to be a good measure of the adequacy of gage shelter and of precipitation catch. The error in sampling of water equivalent for average snow courses is of about the same order of magnitude as the maximum daily change in water equivalent. For seasons of several months' length, observations of gage catch and of accumulated snow on the ground, each at good sites, appear to have comparable precision though there are inherent limitations in the validity of such comparisons.