Spokane is nestled in a broad river valley that extends eastward into north Idaho. The “bowl-shaped” topographical features of the area inhibit the dispersion of air pollutants. Long periods of air stagnation can trap pollutants in this basin, especially during winter when colder, stable air prevails. Weather patterns can positively or negatively affect air quality.
During periods of low pressure with unstable weather patterns (wind or precipitation),warmer air sits near the earth’s surface, with cooler air above. Wind and warmer air mix pollutants and disperse them into the atmosphere.
However, during periods of stable air, an inversion often forms and pollutants can’t disperse as readily. During an inversion, the cooler air sinks beneath the warmer air and becomes trapped at the surface. Smoke from wood burning and carbon monoxide from automobile emissions become trapped in this cooler air and can’t escape into the warmer layer above. The effects of an inversion are felt most commonly after dark, as the night air cools and sinks, making the cooler air layer as shallow as 150 feet.
To learn more about weather: KXLY's Chief Meteorologist, Kris Crocker, provides information as part of "Kris' Weather Kids" program. For more information, click here.