Which Days Will Storms Strike?

Climate Researchers Find More Lightning During Mid-Week, Suspect Truck Peak Emissions

September 1, 2009

Climate researchers found that strong storms and lightning are more likely to occur during the middle of the week due to pollution levels being higher on those days. The researchers speculate that the rise in pollution during mid-week is a result of truck traffic-when emissions peak on Wednesdays or Thursdays. The researchers estimate this may cause a significant increase in lightning strikes on those days than on weekends. As pollution particles rise through storm clouds, water droplets surround them and freeze in a thunderstorm cloud-ideal for triggering lightning.

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Science Insider

LIGHTNING STRIKES ON WEEKDAYS: In a study covering several regions of the United States, researchers found that lightning strikes are 10-20 percent more likely to occur on Wednesdays and Thursdays than other days of the week. Scientists think that there is a relationship between aerosols released by human activity and that may be why lightning strikes peak during the work week. Truck traffic may be one of the main culprits, because their emissions peak around the same time.

WHAT IS LIGHTNING? Lightning is a form of static electricity. We experience static electricity every time we drag our feet on the carpet and then touch a conducting surface, like a metal doorknob. The shuffling causes our bodies to pick up extra electrons. Touching something with a positive charge, like metal, causes the electrons to "jump" across the small gap from our fingers to the object, and we experience a tiny electric shock. Similarly, lightning occurs because clouds become negatively charged as the water droplets inside rub up against each other during the natural process of evaporation and condensation, when moisture accumulates in the clouds. This charge seeks out something with a positive charge -- the ground, ideally -- and the lightning is the "spark" closing the gap between the two.

The American Meteorological Society contributed to the information contained in the TV portion of this report.

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Lightning Research

To Go Inside This Science:
Thomas L. Bell
Tel: 301-614-6197
NASA / Goddard Space Flight Center
Greenbelt, MD 20771
Thomas.L.Bell@nasa.gov

American Meteorological Society
Boston, MA 02108-3693
617-227-2425

Peter Weiss
American Geophysical Union
Washington, DC 20009-1277
pweiss@agu.org
1-800-966-2481

AGU is a worldwide scientific community that advances, through unselfish cooperation in research, the understanding of Earth and space for the benefit of humanity.