When wind shear conditions are strong, air pollution makes thunderstorms less likely to form. But when wind shear is weak, pollution aerosols actually make storms stronger.

 

"This finding may provide some guidelines on how man-made aerosols affect the local climate and precipitation, especially for the places where afternoon showers happen frequently and affect the weather system and hydrological cycle," atmospheric scientist Jiwen Fan of the Department of Energy's Pacific Northwest National Laboratory told E! Science News.

 

Scientists have long known that air pollution affects weather, but previous studies produced conflicting results, with some showing that more air pollution made storms stronger and others showing that less air pollution strengthens storms.

 

Essentially, the team found that water releases heat when it condenses around aerosol particles, which boosts convection and increases updraft speed. Evaporating water droplets cool the surrounding air, which reduces updrafts.

 

"Aerosols in the air change the cloud properties, but the changes vary from case to case. With detailed cloud modeling, we found an important factor regulating how aerosols change storms and precipitation,” says Fan.