May 15, 1998 transcript #: 233-5
Subject(s): rainbows, halos
Title: BRAINSTORM ANSWER: ROUND RAINBOWSA few weeks ago, I asked one of our famous Brainstorm questions where you come up with the answer. Hi I’m Dave Thurlow for the Weather Notebook. The Brainstorm question was this – “where would you have to be in order to see a completely circular rainbow? Now, this question generated a wide variety of responses, including…
“I believe you would have to be standing at one of the poles, either the North Pole or the South Pole looking out over the earth and you would see the complete rainbow.”
A lot of people said that but the biggest problem is that it never rains at the poles. No rain, no rainbow. Others said they see round rainbows all the time:
“I have seen completely circular rainbows many times here in Northern Minnesota around the sun.”
Those are actually solar haloes or ice bows. Light bounces of ice crystals, not rain drops. Now Jonna Davenport who hears us on WPLN in Nashville was one of the many listeners who hit the nail on the head.
“To see a circular rainbow, you’d either have to be in an airplane, on a mountain or a very tall building.”
You can only see a full circular rainbow when you are looking down, like from an airplane or a mountaintop. Rainbows are half circles when the sun is right at the horizon, near dusk or dawn. They would show a full circle if the earth just weren’t in the way, if you were simply high of the ground. The Weather Notebook is produced by the Mount Washington Observatory where nearly circular rainbows are known to appear. We have pictures and further explanations from our listeners, posted on our website mountwashington.org/notebook. Our show is underwritten by Subaru, the beauty of all wheel drive, with major funding provided by the National Science Foundation.