Life in Clouds
Cumulus clouds photo courtesy of the Cloudman.
JB: This is Earth and Sky, with a question that stumped a lot of experts. A listener wants to know, “Does anything live in clouds?”
DB: We talked to scientists – from microbiologists to cloud experts. Every single one said “interesting question” – but no one had a solid answer.
JB: The only life form that there was some agreement on was bacteria. Probably some bacteria do make their way into clouds as cloud condensation nuclei. In other words, they become the tiny suspended particles that serve as the collection points for water vapor – the seeds of cloud-drops and raindrops. These cloud condensation nuclei can be windblown dust, sea-salt, exhaust from combustion – and probably a small fraction are also bacteria.
DB: But it’s probably not accurate to say that bacteria live in clouds. Instead, they just survive their time there. The lifetime of a cumulous cloud is about half an hour. And since air is continuously passing through clouds, the lifetime of a single cloud droplet is much less than that. The bacteria in clouds probably don’t grow or reproduce until they come back in contact with a food source. So they either dry up and die – or fall back to Earth, enclosed inside a drop of rain.
JB: Thanks today the National Oceanic and Atmospheric Administration and to the National Fish and Wildlife Foundation. We’re Block and Byrd for Earth and Sky.
Our thanks to the following individuals and institutions who assisted in the preparation of this script:
Gary M. Barnes, Ph. D Chair, Department of Meteorology University of Hawaii Honolulu, Hawaii
Antony D. Clarke Department of Oceanography University of Hawaii Honolulu, HI
John Laffan, Ph.D. Assistant Professor Microbiology Department James H. Quillen College of Medicine East Tennessee State University Johnson City, TN
Shelley M. Payne Professor of Microbiology The University of Texas at Austin Austin, TX
Author’s Notes:
Thunderstorms last about 1-2 hours. The great sheets of altostratus and stratus clouds can be sustained for many hours, but these clouds do not tap into the air near the surface where the bacteria probably originate.
Additional Teacher Resources
Astrobiology Magazine; NASA: Life in Clouds
This article discusses explores how in 1997 hurricane Nora, which swept over the western United States, delivered surprising evidence of sea salt and microscopic marine life as far inland as Oklahoma. Research aircraft have discovered plankton in high cirrus clouds. This occurrences and other suggest widespread microbial transport in the clouds.
Spaceref.com: The Clouds Sailing Over Our Heads May Be Home to Thriving Communities of Microorganisms
This article discusses a group of Austrian researcher who discovered bacteria in cloud cover over the Alps. They explain that bacteria does live and grow in clouds, and they believe in may trigger rainfall as well as alter climate.
“Cloud Classification”: National Oceanic and Atmospheric Administration, Jetsream?An Online Weather School. www.srh.noaa.gov/srh/jetstream/synoptic/clouds_max.htm
Clouds are classified into 27 different categories that use Latin words to describe the appearance of clouds as seen by an observer on the ground. This site provides thumbnail images of the 27 classifications and a description of each.
