Potential Future Weather Patterns over the Great Lakes Region

Abstract

Evaluating changes in synoptic patterns is tantamount to understanding regional climate change. To date, the synoptic evaluations that have been done regarding climate change output from General Circulation Models have been restricted mainly to examining changes in storm tracks across large areas (the Atlantic Ocean). In this study, output from the Canadian Coupled Climate Model (CGCM1) and the Hadley Coupled Climate Model (HadCM2) are examined relative to present conditions to evaluate potential changes in synoptic patterns over the Great Lakes region towards the end of this century. These models were used as part of the U.S. National Assessment of Climate Change. Both models show a decrease in the number of extremely cold days, an increase in the number of extremely hot days, and an increase in precipitation for the future—particularly for heavy precipitation (> 12.5 mm) events. The Canadian Model shows more of a precipitation increase from December to July. The Hadley Model shows more of a precipitation increase from July to December. Both models show a decrease in surface windspeed and an increase in the number of days with an easterly wind component. Both models exhibit decreases in cyclone numbers for the future. The Canadian Model shows a general decrease in the number of moderately strong cyclones and decreases in each month. The Hadley Model shows a slight increase in the number of strong cyclones but a greater decrease in the number of weak cyclones—especially during the spring. The Canadian Model exhibits significant decreases in the number of anticyclones in summer and significant increases occur in fall but does not exhibit any systematic changes in terms of intensity. The Hadley Model shows a slight increase in the number of weak anticyclones but a greater decrease in the number of strong anticyclones. Most of the decreases occur during the summer—so that the seasonal distribution is more uniform. All of the changes are consistent with changes in the general large scale flow patterns. An understanding of all these synoptic changes provides richness and a more conceptual understanding of how climate change may affect the Great Lakes region.