Climate change: Particle makeup in clouds

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From environmental search web (Liz Kalaugher):

“Understanding cloud processes is key to reducing the uncertainties associated with climate change,” Kim Prather of the University of California, San Diego told environmentalresearchweb. “One of the largest unknowns is which particles form cloud seeds. Our measurements are some of the first measurements to characterize the size and chemistry of the individual cloud seeds in real-time.”

Prather and colleagues from Colorado State University, the University of Wyoming, Naval Research Laboratory, National Centre for Atmospheric Research, Oregons State University and the University of California, San Diego, took measurements from a plane about 8 km high on 7 November 2007 during the Ice in Clouds Experiment – Layer Clouds. They used aircraft-aerosol time-of-flight mass spectrometry (A-ATOFMS) of the residue remaining after water had been evaporated from the cloud’s ice particles. This resulted in the first aircraft-based, single-particle, dual-polarity mass spectrometry measurements.

The team found that mineral dust made up around 50% of the individual ice-crystal residues, and biological particles made up roughly 33%. The remainder was salts such as potassium and sodium chloride, organic carbon mixed with nitrate, and soot. The use of dual-polarity mass spectrometry enabled a clear differentiation between biological particles and carbonaceous inorganic and non-biological particles.

Around 87% of the dust particles were phyllosilicate clays, which are known to be ice nuclei. It looks like the particles had mixed with biological material, as 60% of them contained both organic nitrogen and phosphate, which may have increased the particles’ ice nucleation efficiency.

More Coyote Gulch coverage here.

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