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Here’s a look at the science behind B.C.’s rare purple sunrise

Click to play video: 'B.C. evening weather forecast: Jan. 14' B.C. evening weather forecast: Jan. 14
Meteorologist Kristi Gordon has the Jan. 14, 2022 forecast for Metro Vancouver and British Columbia – Jan 14, 2022

Many residents around the province woke up to a rare sight Friday morning: a purple sunrise.

Why did this occur? First, a quick explanation on why our eyes see certain colours during sunrise and sunset.

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Purple sunrise Jan. 14, 2022.
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Purple sunrise Jan. 14, 2022.
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Purple sunrise Jan. 14, 2022.

As visible light passes through the atmosphere, tiny particles cause certain wavelengths or colours in the light spectrum to scatter. The further the distance, such as at sunrise and sunset when the sun is low on the horizon, the more colours are scattered.

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Purple and blue have the shortest wavelengths so they are scattered out most easily. The remaining colours able to reach our eyes are the ones with longer wavelengths like orange and red.

The exact colour we see depends on how far away the sun is and the amount of particles in the atmosphere such as dust, pollution and water droplets.

Why are sunsets red?.

In the case of a purple sunrise or sunset, cloud cover needs to be present.

Pink wavelengths, caused by the sunrise or sunset, create an optical illusion as they reflect off the base of clouds.

However, when these clouds are dark or the sky behind the cloud is dark, this pink can seem like purple.

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Purple sunrise Jan. 14, 2022.
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Purple sunrise Jan. 14, 2022.

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