(WKBN) – Do you wake up early enough to ever notice dew on the grass or moisture on your car?
What causes that? Well, for starters, we’ll look at a process called radiational cooling. It is a natural process that occurs after the earth cools off at night. During the day, earth’s surface is heated by the sun (even if there are clouds, the sun’s rays are strong enough to penetrate through the cloud cover to heat the surface of the earth). At night, that heat rises and the ground cools off.
The American Meteorological Society classifies dew as: “Water condensed onto grass and other objects near the ground, the temperatures of which have fallen below the dew point of the surface air due to radiational cooling during the night, but are still above freezing.”
In simple terms, once the air temperatures fall to the dew point, the air can no longer hold any more water vapor, and liquid water (dew) begins to form on surfaces, especially the grass.
I explain these processes with graphics in the latest episode of Weather For Kids.