Clean Air PrimerContact UsSan Joaquin Valley Air Pollution Control District
OverviewScienceIssuesHealthSolutionsActivities
Why the Air Gets Trapped?

Normal circulation of air can help keep the pollution at ground level from building up. The temperature of the air is usually warmer near the Earth and gets cooler with increasing altitude. The circulation cycle occurs because the sun warms the Earth and the air close to it during the day. In the evening, the warm air rises as the Earth and the air close to the ground cools.

Graphic of geography and wind motion from the Pacific to the Sierra Nevada

This circulation of air takes pollutants higher in the atmosphere where they disperse. Sometimes pollution is trapped near the Earth because of a thermal inversion which occurs when a layer of warm air traps cooler air and smog close to the ground and keeps it from escaping into the atmosphere. This layer of cool air is "out of order" since warm air is usually closer to the Earth.

Next Next - Visibility - Look into the light ...

Overview

  Air Transport Corridors

  Pollution Sources

  Criteria Pollutants

  Meteorology

  Visibility

  Acid Rain/Snow

  Air Pollution Advisories

  Air Pollution Advisories

In Depth Look

Tell me more...
Inversion layers and how they work.

2006 SJVAPCD. All Rights Reserved.