Bio-particles trigger ice formation in clouds

May 18th, 2009 - 5:01 pm ICT by IANS  

Washington, May 18 (IANS) A recent analysis of ice crystals, collected while an aircraft was flying through clouds, revealed that they were made up almost entirely of either dust or bacteria, fungal spores and plant material.
While it has long been known that micro-organisms or parts of them get airborne and travel great distances, this study is the first to yield in-situ data on their participation in forming cloud ice.

“If we understand the sources of particles that nucleate clouds and their relative abundance, then we can determine the impact of these different sources on climate,” said the study’s author, doctoral student Kerri Pratt, working under Kim Prather, at the chemistry and biochemistry department, University of California San Diego (UCSD).

These are the results of the Ice in Clouds Experiment - Layer Clouds (ICE-L), funded by the National Science Foundation (NSF) and the National Centre for Atmospheric Research (NCAR).

The effects of tiny airborne particles called aerosols on cloud formation have been some of the most difficult aspects of weather and climate for scientists to understand.

In the climate change science field, which derives many of its projections from computer simulations of climate phenomena, the actions of aerosols on clouds represent what scientists consider the greatest uncertainty in modelling predictions for the future.

“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,” said Anne-Marine Schmoltner of the NSF’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.”

Aerosols, ranging from dust, soot, sea salt to organic materials, some of which travel thousands of miles, form the skeletons of clouds. Around these nuclei, water and ice in the atmosphere condense and grow leading to precipitation, said an UCSD release.

Scientists are trying to understand how they form as clouds play a critical role by both cooling the atmosphere and affect regional precipitation processes.

These findings appeared in Sunday’s online edition of Nature Geoscience.

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