Weather and Air Quality

One way weather can affect air quality is through high temperature and bright sunlight - just the conditions when many of us like to be outside. Ground-level ozone forms in the air from other pollutants: volatile organic compounds (VOCs) and nitrogen oxides (NOx). The higher the temperature and the more direct the sunlight, the more ozone is produced. That's why summertime is the time to watch out for unhealthy levels of ozone.

Wind direction also affects ozone and other air pollution levels. On hazy, hot and humid summer days, winds in New Jersey are usually blowing from the southwest. These winds carry air pollution from the Washington, Baltimore and Philadelphia metropolitan areas to New Jersey, contributing to high ozone levels here. These winds also carry the pollution created here to New York, Connecticut and further to the northeast.

Weather can also affect how quickly pollutants move away from an area. Normally, pollutants rise or blow away from their sources without building up to unsafe amounts. But imagine what could happen if the air was trapped inside a giant box. The pollutants can't escape, and after a while they may build up to unhealthy levels. This trapping can happen when winds are slow or calm, and when warm air moves in over cold ground, keeping pollutants close to the surface (an inversion). Inversions can even occur on clear summer nights. This can affect the next day's ground-level ozone concentrations.

An "inversion" is a zone where the air gets warmer as the height above the ground increases. Usually, inversions are accompanied by light or calm winds, which keep the different temperature layers of air from mixing.

"Boundary layer profilers" are instruments that measure temperature, wind speed and wind direction at different altitudes above a point on the earth's surface. You can check the current atmospheric profile above Rutgers University, which is a display of the winds and temperatures above New Brunswick. (That web page requires Netscape 3 or higher, or Internet Explorer 4 or higher).