Lightning and Thunder Paul Flynn Picture from http://www.flickr.com/photos/dagpeak/13436814/
Contents What is Lightning? What causes it/how does it happen Lightning Strokes What is Thunder and what does it have to do with Lightning?
What is Lightning? Lightning “is similar to the electrical shock you have experienced on touching a metal object on a very dry day. Only the intensity is much bigger.” (Lutgens and Tarbuck pg. 296) Part of the cloud becomes negatively charged, other part becomes positively charged. Lightning acts to balances by creating positive or negative flows of current. Most lighting is what is called “Sheet lightning” The other kind is called “cloud-to-ground lightning” and is much less frequent but much more dangerous.
Heat Lightning Besides sheet and cloud-to-ground lighting, there is also a type that most people know as Heat Lightning. This name is given to thunderstorms that are too far away for people to see or hear, so the result is a bright flash in the sky, which usually occurs when there is a warm humid night following a hot day.
What causes Lightning? Rapid vertical movements inside Cumulonimbus. 5 Kilometer level, ice crystals develop. Positive charge with colder regions. Negative charge with warmer regions. Small positive go up, Heavy negative toward base. Surface has net positive charge. Lightning stroke discharges negative region by striking ground.
Lightning Strokes Many very rapid strokes-Flash Individual components-Stroke Strokes begin when cloud releases electrons-Ionizing air Path becomes known as leader Electron flow increases electrical potential-more conductive, more ionizing When close to ground, deposited electrons flow down Return Stroke-electrons continuously extending up As RS moves up, negative charge in channel is brought to ground
Thunder Discharge of lightning heats air Air expands crazy! Produces sound waves Possible to see lightning right away, not hear thunder Happens along long lightning paths Mountains and building delay sound Lightning more than 20 km away has no thunder-Heat lightning
Lightning/Thunder Facts The total energy in a thunderstorm is more than that in an atomic bomb. About 100 US residents are killed each year by lightning. The Empire State building gets struck about 25 times per year. Once lightning strikes, count seconds and divide by 5 (5 seconds =1 mile) Thunder rumbles cause shock waves are created at different altitudes.
What to do during a Thunderstorm If in a forest, seek shelter in a low area under thick growth of trees. If in an open area, go to low place like a ravine or valley. If in open water, get to land and find shelter immediately.
References Britt, Robert Roy. "The Science of Lightning, Thunder and Thunderstorms." Space.com. 2007. Web. 28 Feb. 2010. <http://www.space.com/scienceastronomy/lightning_backgrounder.html>. Lutgens, Frederick K., and Edward J. Tarbuck. The Atmosphere. 10th ed. New Jersey: Pearson Prentice Hall, 2007. Print. Heat Lightning. 2008. Photograph. Flickr.com, Tampa, Florida. Lightning background. 2007. Photograph. Space.com. P1121162. 2007. Photograph. Flickr.com. By Benjamin W. Denver Lightning. 2004. Photograph. Flickr.com, Denver.