Weather Whys; Air Quality

This is weather-wise, everyone likes a nice breath of clean, fresh air, and few people enjoy outdoor activities in a smoggy polluted area. Of course, the number of factories and automobiles in a community have a lot to do with its air quality. Geography plays an important role, too. For instance, polluted air might have a harder time clearing out of a canyon than it would the wide open spaces. But no matter whether you live deep in a valley or on the great plains, the atmosphere's own mechanisms can help clear out polluted air under the right conditions. On a sunny day, solar radiation passes through the atmosphere and warms the ground beneath it. The ground, then, in turn, warms the air right next to it through a process called conduction. Since hot air tends to rise, that warmed air lifts into the atmosphere creating convection currents. Those currents help mix the warmer air with cooler air, and in doing so, they may carry quantities of airborne pollution particles up into the atmosphere and out of a smoggy

area, helping dilute the polluted air with cleaner air from above. On your average summer day, that layer of well-mixed air may extend upwards for thousands of feet, and the result can be greatly improved air quality for people in the affected area. On the other hand, a lack of mixing can sometimes produce a very bad air pollution episode. In a stable atmosphere such as those associated with large areas of high pressure, pollution can be trapped near the ground. If the same conditions persist for several days, the air quality can become so bad it can pose a threat to people living in the area. Whether wise is made possible by a grant from the National Science Foundation and is a service of the University of Oklahoma, our writer is Christine Harbour, our editor is Brian Walkie, for Whether wise, I'm Drew Barlow.