Dust and Microbes from Asia and Africa Impact Rain and Climate in the Western U.S.

Weather is impacted by wind and humidity, but did you also know that it could be affected by dust? Scientists have found that dusty air blowing across the Pacific from Asia and Africa plays a critical role in precipitation patterns throughout the drought-stricken western U.S.

"We've learned that not all of the particles in the air at high altitudes have the same influence on clouds," said Kim Prather, one of the researchers, in a news release. "We're starting to think that these differences contribute to how rain gets distributed."

The scientists detected dust that mostly originates in Asian and Chinese deserts. These particles are swept westward by the jet stream, where they then mix with a variety of other airborne particles, such as sea spray and smoke. Each of these types of particles, known collectively as aerosols, has its own impact on clouds.

"The standard belief is that the more ice you have in a cloud, the more likely you will get precipitation out of it," said Prather. "Our goal is to catch the first stages of ice forming and find out what exactly the chemical constituents are that the ice is forming on."

In order to find out what effect particles and ice have on precipitation, the researchers used single-particle mass spectrometers. These sampled cloud droplets and ice crystals in real time aboard research aircraft. In the end, the scientists detected lots of biological components, such as bacteria and molecules associated with microbial life.

It's possible that the microbes hitch rides on bits of sand, iron and debris from desert regions. These microbes and biological components become mixed with dust as it's transported across the Pacific toward the west coast. These microbes can help characterize the dust.

"Long term, our goal is to be able to predict how much precipitation we can expect to form when certain aerosols such as dust are coming toward us," said Prather. "That's a lofty goal but we're making headway."

The findings will be presented at the 248^th National Meeting & Exposition of the American Chemical Society (ACS).