METEOROLOGIST JEFF HABY
Clouds can both act as a heat shield and a blanket. During the day, clouds act like a heat shield. They reflect a high percentage of the solar
radiation back toward space. Since less solar radiation reaches the surface, this results in the surface being cooler than it otherwise would
have been. This is especially true when the sky condition is overcast. When there are breaks in the clouds, then a large amount of solar
radiation will still be able to make its way to the surface.
At night, clouds act like a blanket. This is because the clouds, like all objects, are continuously emitting longwave radiation. The clouds
result in more longwave radiation being absorbed by the surface. This results in the surface being warmer than it otherwise would have been.
This is especially true for overcast conditions. When there are breaks in the clouds then more longwave radiation can escape into space and
less longwave radiation will be emitted from clouds toward the surface.
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