Rainbows All Around
For sky watchers, a new discovery is as rewarding as finding the pot of gold at the end of the rainbow. Instead of mythical treasure, however, rainbow enthusiasts have found the elusive triple rainbow and the previously unanticipated quadruple rainbow.
The search for a visible triple rainbow began when United States Naval Academy professor of meteorology Raymond Lee presented scientific evidence for the possibility of visible tertiary rainbows at the International Conference on Atmospheric Optics in 2010. With only five scientifically reliable reports of tertiary rainbows in the past 250 years, Lee didn't have much to go on. But after carefully reviewing the details of those reports, he and his colleague Phillip Layen developed a mathematical model to predict the conditions needed for such an event. They predicted that when the sun breaks through dark thunder clouds during a heavy downpour of uniform-sized droplets, a tertiary rainbow could be visible at about 40 degrees from the sun. That means observers have to be looking into the sun's glare in order to see a tertiary rainbow.
KIMBRA CUTLIP is a freelance writer and former assistant editor for Weatherwise.