Here's why southern Alberta sunrises have been lit

·2 min read
Mike MacLean snapped this shot of the sunrise northwest of Airdrie, Alta., looking west, earlier this week. (Submitted by Mike MacLean - image credit)
Mike MacLean snapped this shot of the sunrise northwest of Airdrie, Alta., looking west, earlier this week. (Submitted by Mike MacLean - image credit)

If you're in southern Alberta and you've been up early in recent days, you may have seen them.

Magical, animated colours have offered some of the most beautiful sunrises and sunsets seen in a while.

Submitted by Tab Gangopadhyay
Submitted by Tab Gangopadhyay

"Fall tends to be a really spectacular time in southern Alberta with these beautiful sunrises and sunsets," Kyle Brittain of The Weather Network told the Calgary Eyeopener on Thursday.

"It all comes back to the shape of the land."

Submitted by Nyckie Rea
Submitted by Nyckie Rea

Wait. Go deeper on that, please.

"You see beautiful sunrises and sunsets in all parts of the world, but the reason we get so many in southern Alberta is because of the terrain, because of the chinooks we get from the wall of rock to our west."

Brittain says those chinooks absolutely impact what the sky shares with us.

"You have the jet stream strengthening as a result of an increase in temperature contrast across the continent. That jet stream tends to shift southward and crosses the Rockies. Whenever you have the west-southwest wind crossing the Rocky Mountains, you tend to end up with chinook conditions. You will tend to see these spectacular sunrises and sunsets associated with chinook-type weather," he explained.

A chinook creates an "arch" of cloud cover over the area and at sunrise or sunset the sunlight is coming from below.

Christine Boyd/CBC
Christine Boyd/CBC

"We had an amazing cluster of skies at the end of September, early October. We've had more in the last few days."

But why are the colours so rich and vibrant?

Sunlight usually appears white, but it exists on a spectrum and different wavelengths play a part.

Submitted by @M_KWAD/Twitter
Submitted by @M_KWAD/Twitter

"You have the blue lights, the cooler colours, that have shorter wavelengths. The warmer colours have longer wavelengths. When you have direct sunshine during the day, a lot of that blue, small-wavelength light, tends to scatter off the small particulate matter, gases in the atmosphere," Brittain said.

"As we get into the evening or morning hours, the sun shines through a much thicker slice of the atmosphere, so it's scattered even further by blue light because it's interacting with even more particulate matter, gas molecules. It allows those reds and oranges to reach our eyes."

Submitted by @hifromtanya/Twitter
Submitted by @hifromtanya/Twitter

And are the sunrises longer than usual?

"Those clouds are way up there, they are like 20,000 feet (roughly six kilometres), maybe higher. These sunrises are just long lived. That sun shines on the underside of it for 20 or 30 minutes and it changes hues from red, to orange, to yellow," he said.

"It's just fantastic."

Submitted by @dawnste79109120/Twitter
Submitted by @dawnste79109120/Twitter

With files from the Calgary Eyeopener

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