May 18, 2009

Climatologists Discover Microbes in Clouds

U.S. researchers say a new study of nascent clouds has revealed that a number of microorganisms"”including bacteria, spores and plants"”may play a role in cloud formation and weather patterns.

Computer models have typically been the tool of choice for climatologists attempting to predict emerging weather patterns, partly due to the fact that it is extremely difficult to capture and measure ice crystals as they are forming in young clouds.

The new study, published in the journal Nature Geoscience, describes how the team of researchers was able to pluck ice crystals from the atmosphere and offer the first direct evidence that airborne bacteria exist in clouds.

"By sampling clouds in real time from an aircraft, these investigators were able to get information about ice particles in clouds at an unprecedented level of detail," explained Anne-Marie Schmoltner of the National Science Foundation's Division of Atmospheric sciences.

"By determining the chemical composition of the very cores of individual ice particles, they discovered that both mineral dust and, surprisingly, biological particles play a major role in the formation of clouds."

For the project, a team of scientists from Scripps Institution of Oceanography and the University of California San Diego loaded themselves and a mass spectrometer "“ a lab device used to measure and determine a substance's molecular content "“ into an airplane and made several trips across Wyoming's skies, all the while collecting and analyzing cloud samples.

In past studies, other research teams have also harvested ice crystals from aircraft, but were unable to keep the samples from melting long enough to be analyzed in a land-based lab, essentially making it impossible to be certain of what they were measuring.

"The key to cloud formation is these little seeds [ice crystals] that feed the clouds," said Kim Prather, a co-author of the study.  "We are basically trying to understand what is forming clouds."

Results of their ice particle analysis revealed that roughly 33 percent of the particles found in the crystals were biological matter, while mineral dust constituted another 50 percent.

"The big deal was to be able to measure the chemistry of each particle one at a time," said Prather.

Prather also explained that the samples contained a significant dust from Asia, suggesting that biological particles can be picked up in dust storms to aid in the formation of clouds.

The group was not, however, able to determine whether the biological elements of the crystals were still living because the instruments "smashed them to bits" in order to analyze them.

"They were potentially living," said Prather.  "We can't say for sure."

The possibility that there may be living microbes present in clouds is not, however, entirely shocking to experts in the field of climatology.  Past studies have discovered living bacteria in rainwater, and a number of scientists have theorized that viruses and bacteria may be transported over long distances by clouds.

"It's almost like the biological material is hitching a ride along with the dust," added Prather.

She says that possessing more accurate knowledge of the exact composition of clouds will assist climatologists in forming models and predictions of future patterns of climate change.


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journal Nature Geoscience