Weather Science

Inversions: how the cool air just above your head could create a death cloud.

Being from an old mill city just outside of Boston, I am quite familiar with the effects pollutants have on the surrounding environment. The coughing and wheezing that is associated with poor breathing conditions is a common situation for many in the Rochester area. It is often true that the pollution we suffer from is man-made, but what you may not know is that a certain weather phenomenon known as an inversion can exacerbate these conditions.


An inversion is a deviation from the normal change of temperature with height. In a normal environment, temperatures decrease with height until the stratosphere (about 12 km above the surface). During an inversion there is an increase in temperature with height near the surface caused by a layer of cool, stable air that often sets-up during the early morning hours. This stable air acts as a blocking mechanism or cap on the upward movement of air from near the surface. As a result, any pollution that is emitted within the inversion layer becomes trapped near the surface. You may have seen smoke from a factory spread out horizontally from a smokestack (see photo). This behavior is a telltale sign of an inversion., When pollution is trapped like this for a long period of time, it can have serious health effects..

Rochester in particular is known for having one of the worst air qualities in the entire country. Vehicles and power plant smokestacks are mainly to blame for the extreme levels of sulfur dioxide and other fine particles that can cause health problems. Although recent studies have shown that the effort to improve the Rochester air quality is on the right path, pollutants in a dense area remain detrimental to one’s well being.

Temperature inversions are not random and actually occur more frequently in certain areas or seasons. Surprisingly enough, Rochester oftentimes experiences inversions due to its location.

Inversions can take place in a marine environment. During the spring and early summer when the cold bodies of water are still recovering from the winter, air directly over the body of water will be cool compared to the land. During the day, this shallow layer of cool air can sometimes move onshore with a lake breeze, setting up an inversion near the lakeshore.

Inversions can also occur with frequency throughout the winter months. Much of our frigid Arctic air (assuming we get any this winter) is often very shallow in nature. Directly above the in put of Arctic air, somewhat warmer air can reside. This temperature set-up can once again result in an inversion. As we progress into the winter months it is fair to say inversions will be occurring on a frequent basis in the Rochester area. Even though Rochester air quality is better than it once was, be on the lookout if you happen to suffer from respiratory conditions.