Relationship Between Precipitation and Topography in the Cypress Hills, Saskatchewan

Abstract

Long tenn precipitation records show a trend toward increased precipitation over tiJne in the cypress Hills of Saskatchewan. 'The Cypress Hills are a plateau 300 to 500 matres higher than the surrounding prairies. Detennining the variation of precipitation with the topography of this area is the focus of this thesis. 'Ib investigate this problem an intensive precipitation gaging network was established over a large portion of the Cypress Hills and maintained during the surmners of 1987 and 1988. In addition, a variety of meteorological instn.nnents were set up to record weather conditions affecting the area. Five topographic variables were used to describe the topography surrounding each gaging station. comparisons between these variables and precipitation recorded at the station indicated that elevation and local relief were the lIDSt significant in explaining changes in precipitation. Gaging stations were grouped into three classes, north slope, plateau, and south slope stations to compare precipitation received over the cypress Hills. Analysis of variance indicates that significant precipitation differences occurred across the Cypress Hills. Generally, the greatest precipitation occurs along the steep north slopes with spillover onto the plateau surface. There is a trend to decreasing precipitation on the more gentle southern slopes inferring the development of a rain shadow. The effect of a large glacial spillway dividing the cypress Hills is unclear. Evidence gathered supports roth a decrease in precipitation or no effect upon precipitation associated with the valley. The distribution of precipitation across the Cypress Hills is complex and is highly dependent upon weather conditions. COrrespondence between topography and precipitation is IIOSt apparent when nof.st; air masses generated by cyclonic stonns affect the area. It also appears that thunderstorns which encounter the Cypress Hills are intensified.