The Chinook winds of southern Alberta are a welcome sight to many, but maybe not all Calgarians. Flowing east off the Rocky Mountains, a highly visible wall of cloud, they bring with them a respite from the winter cold. A temperature hike of 20°C or more in just a few hours is common. Yesterday’s Chinook appearance was particularly stunning, captured here in splendid reds and oranges as the sun was setting (Note: No Photoshop or other photo-manipulation software was applied to this image).
The word Chinook is said to be a First Nation (Indigenous Peoples) word for “snow eater”. Snow and ice literally melts away in front of your eyes, due not only to the increasing temperature but also to the drop in humidity and increasing wind speed….the snow transforms into water and also evaporates away more quickly.
Chinooks go by other names around the world. In the Swiss Alps they are known as Foehn (fall) winds and in Argentina they are called (in spanish) Viento Zonda , a dusty blowing across the pampas of Patagonia. Collectively, the scientific term applied to them is Adiabatic.
Like other winds, Chinooks are the result of colliding pressure fronts. Air pressure is lower at high elevation (in the Rocky Mountains) , and greater at low elevations (in the Foothills of the Prairies). When the wind comes down off the eastern slopes, the low pressure air collides with the high pressure air near the base of the mountains. The moisture in the air condenses, warming the winds by releasing latent heat as the wind moves downhill to the east. At the same time, the high pressure air compresses, further warming the air adiabatically. Because they move downhill, Chinook winds are also called katabatic winds.
I mentioned at the start that maybe not all Calgarians welcome a Chinook. Migraine sufferers can be more prone to an attack, something which may be coupled to the low barometric pressure. According to Dr Steven Graff-Radford, director of the program for headache and oro-facial pain at Cedar-SinaiMedical Center, Los Angeles, barometric pressure changes might affect pressure in the brain or the way in which the brain blocks pain, although the phenomenon has not been fully worked out. Personally, I suspect that the decrease in humidity and drying out of the air may also be a contributing factor (it is very easy to become dehydrated in Calgary’s dry winter).
In the balance though, many people psychologically feel “better” from these winds. No doubt because things warm up, giving a break from winter’s sub-zero temperatures. Certainly for me taking this shot yesterday, the “wow” factor gave me a great sense of well-being in winter.