What is an inversion?
An inversion is a stable zone in the atmosphere. Inversions that are weak may only last a day while strong inversions can stay around for multiple days until the weather changes. During a strong inversion, pollution is trapped under this “cap”, preventing exhaust like carbon monoxide from vehicles and wood stoves to mix or rise up in the atmosphere.
How do inversions form?
An inversion is caused when the air near the ground is colder than the air in the atmosphere. Warm air is lighter than cold air so when an inversion forms the air is very stable.
www.airnow.gov/inversion.html
Types of Inversions
There are two major types of inversions; aloft inversions that take place above the ground, and surface inversions take place near the surface of the earth. Surface inversion formed through the cooling of air near the surface during the night. After the sun sets, the ground cools off rapidly this in turn cools the air that is in contact with the ground. This process is known as radiative cooling of lower layers. Because air is a poor conductor of heat, the air aloft the ground remains warm.
Surface inversions usually form during a mild wind, clear sky that lasts most of the night. A breeze will prevent warmer air in the atmosphere from mixing with the cool air on the ground and a clear sky will enhance the rate of cooling on the surface of the earth. The nights during the winter season are long and usually have clear skies, and the surface inversions are much stronger.
