Thursday, January 24, 2013

surface temperature inversions

The most common manner in which surface inversions
form is through the cooling of the air near the ground at
night. Once the sun goes down, the ground loses heat
very quickly, and this cools the air that is in contact with
the ground. However, since air is a very poor conductor
of heat, the air just above the surface remains warm.

Conditions that favor the development of a strong
surface inversion are calm winds, clear skies, and long
nights. Calm winds prevent warmer air above the
surface from mixing down to the ground, and clear skies
increase the rate of cooling at the Earth’s surface.

 Long nights allow for the cooling of the ground to continue
over a longer period of time, resulting in a greater
temperature decrease at the surface. Since the nights in
the wintertime are much longer than nights during the
summertime, surface inversions are stronger and more
common during the winter months. A strong inversion
implies a substantial temperature difference exists
between the cool surface air and the warmer air aloft.

During the daylight hours, surface inversions normally
weaken and disappear as the sun warms the Earth’s
surface. However, under certain meteorological
conditions, such as strong high pressure over the area,
these inversions can persist as long as several days. In
addition, local topographical features can enhance the
formation of inversions, especially in valley locations.

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