Cooling at Night, Cloudy versus Cloudless Skies.

Clouds at night often cause warming at the surface of the Earth. The figures below illustrate this effect. On clear nights energy radiated from the surface of the Earth as long wave (infrared) radiation has a freer path to the top of the atmosphere. The result is enhanced cooling compared to nights when clouds block and reradiate some of this energy. The figures below illustrate this effect.