Research points to fewer droughts


Precipitation has been below normal in much of the eastern Prairies, going back to the wet fall of 2019.

However, this period of dry weather runs contrary to a larger trend.

Over the last 50 to 70 years, the northern United States Plains and the Prairies are getting warmer and wetter.

A U.S. Department of Agriculture study published April 6 found that the southwestern U.S. is receiving less rainfall than it did in the past and the number of days between rainfalls is getting longer.

Scientists from the USDA and the University of Arizona studied data from 337 weather stations across the western U.S. from 1976 to 2019.

The data showed less rain in states like Arizona, but also showed that Idaho, Washington, Montana and North Dakota are getting more rain.

“In these regions, the researchers found some increases in total annual rainfall and decreases in drought intervals. Together, these changes support what models have predicted as a consequence of climate change: a northward shift in the mid-latitude jet stream,” said a USDA news release about the study.

The findings do apply to Western Canada, said Barrie Bonsall, a research scientist with Environment Canada in Saskatoon.

Canadian climate data shows that droughts are becoming less frequent on the Prairies and rainfall is increasing, on average.

That phrase, “on average,” is critical to remember.

“You’re looking at a long-term trend, super-imposed on ups and downs, ups and downs,” Bonsall said.

“In any given year… (it) can deviate from that trend.”

It’s hard to notice such a trend when there’s been little rain or snow for seven months, but that’s the nature of the Prairies.

“The variability (from) year to year, and even decade to decade, is so great in this area,” Bonsall said. “(But) you have to take a step back and (look) at, what’s the long-term line.”

That line, the average amount of precipitation per year, has been going up.

It’s hard to know if the average amount of precipitation will continue to increase during the 2020s.

Western Canada could be entering a dry spell over the next decade, or a wet spell.

What’s more probable is that extreme weather will occur more often.

Last year on June 28, 155 mm of rain fell on Brandon in one day.

That storm represented about 40 percent of all of Brandon’s precipitation for 2020. As temperatures rise, such massive storms are more likely.

“With the warming atmosphere, it’s able to hold more moisture. Your probability of getting 150 mm of rain (on a given day) is increasing,” Bonsall said. “We would expect more of those (events) in the future.”

As well, with warming temperatures there’s been a decline in average snowfall across Western Canada, but an increase in rainfall, on average, each year.

That’s because of warming weather in the shoulder seasons, during months like April, October and November.

So, a place like Weyburn is more likely to get rain in April rather than snow.

“If you look on average, over a long period of time, we’re getting more Aprils above zero than we are below (zero),” Bonsall said.

“Instead of it falling as snow, it’s coming as rain.”