Precipitation trends on the Canadian prairies

The Canadian prairies are a major producer of grain, much of which is produ ced under rain-fed agriculture. The amount and timing of precipitation are critical to grain production. Information on the precipitation trend is the refore vital to this region. Regression analysis was used to establish line ar trends of precipitation amounts, number of precipitation events, and var iance of precipitation at 37 stations with 75 yr of record across the Canad ian prairies. The precipitation was further split into rainfall and snowfal l, and similar analysis was performed on these variables. The analysis show ed that there has been a significant increase in the number of precipitatio n events mainly due to an increase in the number of low-intensity events. A s such,precipitation events are not getting more intense on the Canadian pr airies. The number of precipitation events (excluding events that are 0.5 m m or less) has increased by 16 events during the last 75 yr. Precipitation and rainfall amounts have increased significantly by 0.62 and 0.60 mm yr(-1 ), respectively, on the Canadian prairies during the last 75 yr. During the period from 1921 to 1960 the trends in precipitation, rainfall, and snowfa ll were not statistically different from zero. However, from 1961 to 1995, snowfall has declined significantly by 0.95 mm yr(-1). The trends in the mo st recent period (1961-95) were also significantly different from those in the 1921-60 period for snowfall. The difference in trends between the two p eriods for snowfall, combined with the inverse relationship in the rainfall -snowfall trends, suggest that these trends may be related to climate chang e.