Sunday, March 18, 2007

Chinook Train

Canon EOS 20D with 10-22 @ 10mm

I shot this photo of the C-Train hurtling into downtown Calgary under a Chinook Arch as the rising sun projects its rays onto the towers in the city core. I had been on the phone talking to my friend Brian in Edmonton earlier in the week and I had mentioned that we were experiencing a Chinook in Calgary. Brian said to me "Why don't you shoot a photo of a Chinook Arch and place the photo on your blog". It made me realize, what we in Calgary and Southern Alberta take for granted, might be of interest to those of you who have heard of a Chinook Arch but have not seen one.

What exactly is a Chinook Arch you ask? The Chinook Arch is one of the most striking feature of a Chinook. The arch is a band of stationary stratus clouds caused by air rippling over the mountains due to orographic lifting. To those unfamiliar with the chinook, the chinook arch may look like a threatening storm cloud at times. However, they rarely produce rain or snow. They can also produce stunning sunrises or sunsets.

The eastern-slope chinook phenomenon is a Fohn wind that results from the movement of high and low pressure systems over the Rockies seen in the second photo. As the wind moves over and through the mountains, the moisture in the air condenses and falls as precipitation, warming the air by releasing latent heat. Then the air is warmed and dried. as the air descends the eastern slope of the Rockies. Warm air descending this slope can displace an existing cold, moist air mass and increasing the temperature that Calgarians look forward to upon the arrival of a Chinook.

Quite often, when the west coast is being hammered by rain, the windward side of the Rockies is being hammered by snow, and on this side of the Rockies, Alberta is basking in a Chinook. Of course chinooks are not necessarily loved by all as it is said that chinook winds can cause a sharp increase in the number of migraine headaches suffered by people such as my sister Sonia who suffers from these Chinook headaches.

These frequent midwinter thaws in Southern Alberta's chinook country are more a bane than a blessing to gardeners. Plants can be visibly brought out of dormancy by persistent chinook winds, or have their hardiness reduced even if they appear to be remaining dormant. In either case they become vulnerable to later cold waves. Plants that do well in areas where constant cold maintains dormancy all winter are difficult in our chinook country as I can attest to. Now that I bored you to death, I will hang up...

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