.jpg){kind=link}
Calgarians know all too well how unpredictable the weather can be, but what causes this unpredictability?
Chinook winds — most commonly known as chinooks — cause a considerable temperature change year-round in Calgary and the surrounding area. Yet Calgarians notice these temperature changes in winter when temperatures can drop into the high negatives.
Global News Calgary’s chief meteorologist Tiffany Lizée describes chinook winds as moist, westerly air flows that hit the Rocky Mountains. As the air travels up the mountains, it dries out. The drying process causes condensation in the form of rain or snow.
“We could get that snow and then all of a sudden a chinook comes in and melts it. Once we get deeper into winter, it’s harder to melt that snowfall because you get that cooling effect off of the snow that’s already settled,” added Lizée. “It takes a lot more than just a chinook or two to melt that, depending on how thick the snowpack is.”
The condensation process happens on the windward side—meaning facing toward the wind—which typically affects our neighbours to the west, British Columbia.
The now-cooled air gathers and moves toward Calgary on the left side, away from the wind. As the air moves down the mountains, it warms up due to the heat released during condensation, which people associate with chinooks—warm, dry wind.
This phenomenon occurs worldwide in regions with long stretches of mountainous terrain and goes by various names, such as föehns in southern Europe, the Zonda in Argentina, Northwesters in New Zealand, and Bergs in South Africa.
Meteorologists can predict these warm winds, sometimes known as “snow eaters,” up to ten days before they occur.
“If there’s a strong low-pressure system building over the Pacific [Ocean] and it’s tracking toward southern Alberta…we can usually see that the airflow will track into our neck of the woods,” said Lizée.
Impacts on Calgary’s road maintenance
According to a 1997 study by the University of Calgary’s Lawrence Nkemdirim, “Chinooks occur in southern Alberta because the region lies between the foothills and the eastern slopes of the Rocky Mountains.”
Nkemdirim says that chinook winds can help the city with its road maintenance budget when they are strong, as they cause a significant increase in temperature.
On the other hand, the city may find it challenging to plan for road maintenance within its $55 million budget for the year.
Calgarians appreciate Chinook winds every winter, as they keep the city safe from long periods of below-freezing temperatures. But these respected winds have their own set of faults.
According to a 2000 study by University of Calgary researchers, “Chinook weather conditions increase the probability of migraine headache occurrence.”
For some people, chinooks can trigger piercing headaches, referred to as “chinook migraines.” Migraine sufferers seem especially vulnerable to this effect.
Edwin Cey, who heads the University of Calgary’s Department of Earth, Energy, and Environment, knows “chinook migraines” well.
“I actually happen to suffer from migraines, and I know over the years, I’ve tracked what some of my triggers are, and chinook weather events are a particular trigger for me,” said Cey. “As I know, they are for many other migraine sufferers.”
Environmental impact: chinooks, drought, and agriculture
Cey’s area of research focuses on hydrologic processes — water movement on land and below the surface.
Chinooks absorb moisture and cause soil to dry out.
“So we’re what’s called a relatively semi-arid climate [which] makes it difficult to grow things,” said Cey. “That’s why farmers are relying on irrigation because it’s a relatively dry area.”
The dramatic shift in temperature has other effects on our environment.
Further west, in the Rockies, chinooks can trigger wind slab avalanches. Wind slabs form from the wind, which creates one or more layers of stiff snow. According to Avalanche Canada, broken snow crystals pack together to form wind slabs.