Accuracy of Canadian Snow Gage Measurements

Abstract

Field investigation to assess the accuracy and comparability of precipitation gage measurements of snowfall in Canada was initiated in 1973. The MSC Nipher shielded snow gage (Canadian standard gage), the Universal (Belfort) precipitation gage, and the Fischer and Porter precipitation gage were tested at open and sheltered sites. Shielded and unshielded pairs of gages were compared at an open site. Gage catch was related to ?ground true? snowfall water equivalent as measured on snow boards in a sheltered site. Each gage tested had unique performance characteristics. Curves of gage catch to ground true as a function of wind speed are given. The catch ratio of the Universal gage is higher than the Fischer and Porter for similar shielding and environmental conditions. The MSC Nipher shielded gage exhibits a superior catch efficiency. At lower wind speeds this gage can overcatch. For winds up to 5.5 m s?1 the catch of the Nipher gage is within 10% of true. A mean correction of 0.15 mm for retention loss is required for this non-recording gage. Reasons for the efficiency of this gage are suggested. Users of gage measurements of snowfall water equivalent in Canada must consider the method of measurement before analyzing or correcting snowfall data.