Agricultural cultivation and thunderstorm patterns in the prairies

There seems to be a link between weather patterns and the kind of crops grown on Canada's Prairies. The widespread agricultural cultivation in the Prairies appears to have had an impact on the frequency and severity of thunderstorms in the region.

The conversion of nearly 60 per cent of Canada's prairie grasslands from native mixed grasses to annual crops has altered the pattern of evapotranspiration—the natural process by which plants release moisture back into the atmosphere—according to an Environment Canada study. This process is known to be at least partially responsible for the formation of weather conditions that cause thunderstorms.

The study shows a strong similarity between the evapotranspiration curve for spring wheat—the dominant crop in the Prairie eco-climatic zone—and the seasonal pattern for thunderstorms. Before crops emerge, as they age, and after they have been harvested, low evapotranspiration rates make thunderstorms less likely and probably less frequent. In the middle of the growing season, when rapidly expanding foliage and seed production cause high evapotranspiration, such storms are more likely and may be more frequent. The study also suggests that regional mid-summer thunderstorms are more severe, on average, than they were before the introduction of agriculture.

Observational studies done in the Great Plains region of the United States have also linked high evapotranspiration rates to increases in the frequency of both hail and tornadoes.

The research is helping to develop a better understanding of the impacts agricultural practices can have on Canada's climate.

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