Tiny particles found to have a huge impact on the weather

A new study by 21 experts from 15 institutions around the world has revealed that the tiniest particles can have a major influence on the weather. The research demonstrates how particles smaller than one-thousandth the width of a human hair can intensify storms and rainfall events.

The small airborne particles, which are known as aerosols, come from many sources including industrial air pollution and wildfires. While it has been believed that aerosols may play an important role in the weather, the new research suggests that these particles have a much bigger influence than what scientists had anticipated.

Jiwen Fan is a researcher at the Department of Energy’s Pacific Northwest National Laboratory and the lead author of the study.

“We showed that the presence of these particles is one reason why some storms become so strong and produce so much rain,” said Fan. “In a warm and humid area where atmospheric conditions are otherwise very clean, the intrusion of very small particles can make quite an impact.”

The research was conducted using ground-based and airborne measurements related to climate during 2014-2015 from the research campaign GoAmazon.

The study was focused on data from one region in the Amazon, in particular. Manaus is the largest city in the Amazon with a population of more than 2 million people, yet the city is surrounded by pristine Amazon rainforest. This setting gave the researchers a rare opportunity to look at the impact of atmospheric particles and processes in a largely pre-industrial environment.

Scientists set out to closely examine the role of particles less than 50 nanometers wide in the development of thunderstorms. Larger particles that are similar to those observed in the study are known to create clouds and play a role in creating water droplets that fall like rain, but this is the first time that scientists discovered that smaller particles have this same effect.

In fact, computer simulations showed that the smaller particles have an even more powerful impact on the formation of clouds and precipitation than the larger particles.

“We’ve shown that under clean and humid conditions, like those that exist over the ocean and some land in the tropics, tiny aerosols have a big impact on weather and climate and can intensify storms a great deal,” said Fan. “More broadly, the results suggest that from pre-industrial to the present day, human activity possibly may have changed storms in these regions in powerful ways.”

The study is published in the journal Science.

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By Chrissy Sexton, Earth.com Staff Writer