Science of winter: Why early-morning sunshine can make the air colder

By Tom Spears, Ottawa Citizen, January 2, 2019

There’s an oddity that David Phillips has noticed on clear, still winter mornings: The sun comes up, and the air keeps getting colder.

It doesn’t happen every day, but he says it happens fairly often, and it’s no illusion. (A case in point was Wednesday, when the air at 8 and 9 a.m. was colder than at 5 and 6 a.m.)

And the reason is a complex relationship between the sun, the ground, and the different layers of air near ground level.

Phillips, the senior climatologist at Environment Canada, explained it in an interview.

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