| Making Rain - Science Insider
Reported June 2009
HOW STORMS DEVELOP: Storm clouds form as moisture evaporates from the earth into the atmosphere. The air cools off rapidly as it reaches higher altitudes. Sometimes a cold front -- where the cold air from one air mass meets the surrounding air -- will force warm, moist air upward into the colder air. This cools the water vapor and it condenses onto dust and dirt particles in the air, called condensation nuclei, collectively forming clouds. Nuclei made of ice are usually present before rain or snowfall. The process continues: More and more water vapor turns into liquid, and the moist air gets warmer and rises higher and higher. A thunderstorm results. New research demonstrates most condensation nuclei are actually biological in origin, with bacteria at the core.
ICE PARTICLES ALSO LINKED TO LIGHTNING: The relationship between the number of lightning strikes and how many ice crystals are present in clouds is the same regardless of different atmospheric environments over oceans, coasts and continents. The relationship between ice and lightning, in comparison, does not show this same level of consistency. The results support previous assumptions about the basic physics of lightning and ice. As a result, the amount of lightning in a storm could be used in the future to predict the amount of ice that is present.
The American Meteorological Society and the American Geophysical Union contributed to the information contained in the TV portion of this report.
If you would like more information, please contact:
Brent C. Christner
Louisiana State University
Baton Rouge, LA 70803
(225) 578-1734
http://www.biology.lsu.edu/faculty_listings/fac_pages/bchristner.html American Meteorological Society
Boston, MA 02108-3693
(617) 227-2425
http://www.ametsoc.org
Peter Weiss
American Geophysical Union
Washington, DC 20009-1277
(800) 966-2481
http://www.agu.org
pweiss@agu.org
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