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 snow fall. 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 that 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 much 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.