ASU Research E-Magazine: Smoggy Skies, Soggy Skies

After a tough week at work or school, nothing sounds better than a weekend of fun in the sun. Unfortunately, that work week may be responsible for rained-out ball games and soggy picnics on Saturday and Sunday.

Two ASU climatologists have discovered a link between air pollution and weather patterns on the Atlantic coast of North America. It seems that car exhaust and factory smoke produced during the week may lead to a pattern of rainy weekends.

To get their results, Randy Cerveny and Robert Balling, Jr. studied daily carbon monoxide and ozone measurements collected at a Canadian monitoring station located on an island off the coast of Nova Scotia. Carbon monoxide and ozone are two common air pollutants.

They also studied rainfall data gathered by weather satellites in orbit over the Atlantic Ocean, and information stored in databases of Atlantic hurricane measurements. They found that weather on the East Coast of the United States is likely to be rainy on weekends and clear during the week. They also found that pollution hits its highest levels at the end of the week—possibly causing the weekend showers.

“The dirt and dust, the solid parts of the pollution, tend to absorb heat. That makes the air around those parts warmer. Warm air rises. As warm air rises, it tends to cause clouds and precipitation,” says Cerveny, an ASU professor of geography.

The researchers believe the seven-day pollution pattern is caused by the human work week, because nothing in nature follows a seven-day cycle. The seven-day week is a purely human creation.

Not surprisingly, activities that cause pollution tend to happen on weekdays, so it makes sense that pollution levels peak at the end of the week.

“[Pollution] primarily comes from auto exhaust and from factories. It’s the nasty stuff that helps to create the brown cloud we see over Phoenix,” Cerveny says.

Balling and Cerveny also found a link between pollution patterns and hurricanes. Weekend hurricanes tend to be much weaker than storms that occur Monday through Friday.

Hurricane wind speeds can drop by 10 miles-per-hour on the weekend, knocking them down a whole category on the Saffir Simpson Scale, a tool used by scientists to rate the strength of hurricanes and other cyclonic storms.

Cerveny and Balling only studied the Atlantic coast. As western cities grow, some people wonder whether or not their weekends might get wetter as well.

Cerveny doubts it. “Winds flow from west to east,” he says. “While it is possible that pollution from areas in southern California may affect our weather here [in Arizona], it’s unlikely to affect the West Coast.”—Diane Boudreau