Airborne Particles Affect Precipitation

FORT COLLINS, Colo., June 9 (UPI) — U.S. scientists say they’ve discovered for the first time that large airborne particles of dust and pollen can create greater amounts of precipitation.

Colorado State University atmospheric researchers said they found the amount of ice crystals necessary to form precipitation in clouds is linked to the abundance of larger aerosol particles in the atmosphere. Using that finding in a global climate model, the scientists also discovered clouds have a stronger cooling effect on the Earth than had been previously estimated.

However the study leaders — research scientists Paul DeMott and Anthony Prenni — said future increases in the ice nuclei for cold clouds would reduce the cooling impact on climate and vice versa.

“The catalysts for most ice nuclei are primary emissions — from pollution or sea spray or dust,” DeMott said. “The bigger the particles, the better it is for ice nuclei.” At the same time, pinpointing a number of particles at a specific temperature is too simple for climate models to accurately represent what’s occurring in nature, he added.

The study appears in the Proceedings of the National Academy of Sciences.

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