Amount of dust, pollen matters for cloud precipitation, climate change

Science Daily: A lot of large particles of dust and pollen in the atmosphere may make your nose twitch, but they can lead directly to greater precipitation in clouds, Colorado State University atmospheric scientists have discovered for the first time.

The amount of ice crystals necessary to form precipitation in clouds is linked to the abundance of larger aerosol particles in the atmosphere, according to a study by Paul DeMott and Anthony Prenni, research scientists in the Atmospheric Science department at Colorado State. Their findings appear in this week's issue of the Proceedings of the National Academy of Sciences.

Using these new findings, a global climate model predicted that clouds have a stronger cooling effect on the globe than previously estimated. However, future increases in these ice nuclei for cold clouds would reduce the cooling impact on climate and vice versa, the scientists found.

Special particles called aerosols -- resulting from desert dust, some biological processes and possibly from pollution -- are needed as catalysts to form ice in clouds, which can influence precipitation and cloud dynamics. These particles can serve as the center, or nuclei, for cloud droplets that combine to form raindrops. "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, DeMott said…..

Clouds shot by Ted Garvin, Wikimedia Commons, under the Creative CommonsAttribution-Share Alike 2.5 Generic license