Assessment of potential effects of climate change on heavy lake-effect snowstorms near Lake Erie

The potential effects of future climate change on the frequency of heavy lake-effect snowstorms in the Lake Erie snowbelt were assessed using recent transient simulations from two General Circulation Models (GCMs): the second-generation Hadley Centre (HadCM2) and the first generation Canadian Climate Centre (CGCM1) coupled ocean-atmosphere models. An analysis of historical heavy lake-effect snowstorms identified six weather conditions to be closely related to heavy lake-effect snowstorm occurrence: surface wind speed > 6 m/s, surface wind direction of south southwest to west northwest, surface air temperature in the range of -10degreesC to 0degreesC, lake surface to air temperature difference > 7degreesC, lower tropospheric stability (T (lake) - 850 > 15degreesC), and a highly amplified middle tropospheric wave train. These criteria were applied to daily grid point data from the GCMs for two periods, the late 20(th) Century and the late 21(st) Century, to determine the relative frequency with which heavy lake-effect conditions were predicted. Surface conditions favorable for heavy lake-effect snow decreased infrequency by 50% and 90% for the HadCM2 and CGCM1, respectively, by the late 21(st) Century. This reduction was due almost entirely to a decrease in the number of occurrences of surface air temperature in the range of -10 to 0degreesC, which in turn was the result of an increase in average winter air temperatures. Other surface conditions favorable for lake-effect snow occurred at about the same frequency in the late 21(st) Century as in the late 20(th) Century, suggesting that lake-effect rain events may replace lake-effect snow events. Changes in the middle tropospheric wave train were also noted in both models. However, there were sizable biases in the simulation of the present-day climate, raising questions about the validity of the future projections.