Smog

 

Smog

Although freezing rain, thunderstorms, and tornadoes are significant weather events, one of the most important things impacted by an inversion layer is smog. This is the brownish-gray haze that covers many of the world’s largest cities and is a result of dust, auto exhaust, and industrial manufacturing.

Smog is impacted by the inversion layer because it is, in essence, capped when the warm air mass moves over an area. This happens because the warmer air layer sits over a city and prevents the normal mixing of cooler, denser air.

The air instead becomes still and, over time, the lack of mixing causes pollutants to become trapped under the inversion, developing significant amounts of smog.

During severe inversions that last over long periods, smog can cover entire metropolitan areas and cause respiratory problems for the inhabitants.

In December 1952 such an inversion occurred in London. Because of the cold December weather, Londoners began to burn more coal, which increased air pollution in the city. Since the inversion was present over the city, these pollutants became trapped and increased London’s air pollution. The result was the Great Smog of 1952 that was blamed for thousands of deaths.

Like London, Mexico City has also experienced problems with smog that have been exacerbated by the presence of an inversion layer. This city is infamous for its poor air quality, but these conditions are worsened when warm subtropical high-pressure systems move over the city and trap air in the Valley of Mexico.

When these pressure systems trap the valley’s air, pollutants are also trapped and intense smog develops. Since 2000, Mexico's government has developed a plan aimed at reducing ozone and particulates released into the air over the city.

London’s Great Smog and Mexico’s similar problems are extreme examples of smog being impacted by the presence of an inversion layer. This is a problem all over the world, though, and cities like Los Angeles, Mumbai, Santiago, and Tehran frequently experience intense smog when an inversion layer develops over them.

Because of this, many of these cities and others are working to reduce their air pollution. To make the most of these changes and to reduce smog in the presence of a temperature inversion, it’s important to first understand all aspects of this phenomenon, making it an important component of the study of meteorology, a significant subfield within geography.