Pesky clouds

Dec. 10- This happens a lot in the winter: not only is it cold, the days are short so there is not much sunlight to soak up, but to add insult to injury, we have plenty of cloudy days, sometime for many days on end.  Why does this happen?

Cold air is dense, so it naturally sinks and hugs the ground. It is hard to dig that air out, so relatively warmer air can sit on top of that layer of air.  This results in a stable atmosphere; warmer air rises, colder air sinks, so you little air movement that would help remove this setup.  We can this an inversion.

Inversions can cause a layer of clouds to stay persistent for days.

Inversions can cause a layer of clouds to stay persistent for days.

During the summer, the sun is able to heat up the ground (which heats the air above it), and remove that inversion by warming the cool, surface air to the point where it can start rising and “break” the inversion (or rise into the warmer air above it).  This promotes mixing in the atmosphere, helping “burn” off any fog, cloud cover, etc. that forms when the atmosphere is very stable.

Lack of adequate daytime heating does not help burn off the cloud cover.

Lack of adequate daytime heating does not help burn off the cloud cover.

The downside in the winter, is that the sun’s angle is low on the horizon (we aren’t getting as direct of sunlight to the earth as we would in the summer), and the days are short, cutting down on the amount of time the sun can heat the earth.  Without adequate heating, this inversion can stay in place for a while.  There is also plenty of cold air to go around in the winter.  As a result, cloud cover stays stubborn for days on end.

For us this week, high pressures is moving in from Michigan (high pressure can help dry the air out by promoting downward movement in the atmosphere, which is why we generally have sunny days with a high moving in), and warmer weather is flowing in from the west.  Between those two, we should see the pesky clouds get cleared out before the end of the week.

Next time we see a long stretch of cloudy days this winter, remember this article and how this all works!

-Alex

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Posted under weather

This post was written by Alex Kirchner on December 10, 2014

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