What is a temperature inversion and what problems can it cause?

Normally, the temperature of air is cooler up high and warmer down below. This occurs because warm air expands and cools as it rises. A temperature inversion is when the temperature of air is warmer up high and cooler down below.

There are two types of temperature inversions:

• 
  Surface Inversions: temperature inversions which occur near the Earth's surface

• 
  Aloft Inversions: temperature inversions which occur above the ground

Conditions that favor the formation of a temperature inversion include: long nights (winter), clear skies, and calm winds. Geologic features such as valleys may enhance the formation of temperature inversions. A temperature inversion may last for several days.

Temperature inversions can create several problems:

• Temperature inversions can trap pollutants near the surface and contribute to poor air quality.

• Temperature inversions can trap sound near the surface and may cause noise to sound louder.

• Temperature inversions may prevent thunderstorms from forming.