Weather Whys; Ionosphere

This is weather-wise. If you've ever listened to the radio late at night, you may have been surprised to find that you could pick up stations hundreds or even thousands of miles away. Those distant programs are yours, courtesy of the ionosphere. That's a region high in the atmosphere that contains a large number of electrically charged particles. There are three major parts of the ionosphere called the DE and F regions. The D region is closest to the Earth, starting at an elevation of about 40 miles. The E is next to it, beginning around 60 miles, and the F is farthest away at about 90 miles. Now AM radio waves go out in a straight line from the transmitter, but the surface of the Earth is curved, so eventually the AM waves path takes them high into the atmosphere. When they encounter the D region of the ionosphere during the day, some of those waves are reflected back to Earth, but most are either absorbed or scattered.

At night, however, the D region essentially disappears, and the AM radio waves are being reflected off the E and F layers. Those regions don't weaken the waves like the D region does, so the waves make it back to Earth, and even though they may be hundreds of miles from their station, you can still pick them up with very little problem. That means earthly entertainment is coming to you through the highest regions of the atmosphere. Weather-wise is produced with the assistance of the National Weather Service Forecast Office, and the National Severe Storms Laboratory, both in Norman, Oklahoma, and the Cooperative Institute for Mesoscale Meteorological Studies, the Oklahoma Climateological Survey, and the School of Meteorology, all at the University of Oklahoma. Weather-wise is made possible by a grant from the National Science Foundation, but whether wise, I'm Drew Barlow.