Clouds of the Day - Monday, December 21, 2020

As you can see the day began with a clear sky. The first photo on the left was taken before the Sun climbed above the southeastern horizon. The bright light across the bottom of the photo is sunlight being scattered by the rising sun. Across the top of the photo is darker sky. The atmosphere higher in the sky is still dark because the sunlight has not reached it yet. As the sun rises higher the entire sky will brighten.

The stratocumulus clouds below are caused by cold advection. As temperatures warmed in the morning the air became weakly unstable in the lower levels. Because there was sufficient moisture available, the rising air cooled to its dew point and condensed in to stratocumulus clouds. Stratocumulus are not very deep because the atmosphere above the cloud tops includes sinking motion which warms the air creating a stable layer of air above the rising clouds below. This stops the rising motion and keeps the clouds in the low levels of the atmosphere.

Sunrise

Stratocumulus

Stratocumulus

Stratocumulus