During winter, high pressure systems lead to cold temperatures, stagnant air, and a build up of pollutants in the air. Wind , rain and snow storms are sometimes called scrubbers because they help clear out the air pollution. A temperature inversion is when a layer of warm air sits on a layer of cold air and pollutants. During most other weather conditions, warm air is near the ground and the air can rise easily and carry away pollutants . In a temperature inversion the reverse is true.
Cold air is trapped near the ground by a layer of warm air.
Warm air acts like a lid , holding pollutants down where we breathe . During winter, smoke from fireplaces and wood stoves is a major source of pollution in Spokane. During an inversion, smoke from chimneys can't rise and our neighborhoods can get smokey. That's why, if there's too much smoke in the air, a burn ban may be issued to reduce or stop the use of wood burning devices. Another major source of air pollution in Spokane is from automobiles .