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 -10°C to 0°C, lake surface to air temperature difference > 7°C, lower tropospheric stability (T _{lake - 850} > 15°C) 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 in frequency 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 0°C, 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.