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A weather Doppler is a device used to detect severe weather conditions, based on a principle described by Christian Doppler in 1842. The devices are now being used to predict weather in stations located in various centers around the United States.
Christian Doppler was a professor of mathematics and astronomy. He presented a paper that explained the principle that was named after him entitled, "On the Coloured Light of Double Stars and Certain Other Stars of the Heavens." Doppler described how the frequencies associated with light and sound waves varies, depending on where they are coming from. The location of the device observing the waves also plays a part. This principle formed the basis for the idea that weather patterns could be tracked by observing radio waves.
The United States National Weather Service started installing weather Doppler devices in the 1980s, completing the project by the early part of the 1990s. Weather stations aren't the only locations where Doppler radar can be found. Some television stations have invested in buying their own equipment. Others get their information from National Weather Service installations.
The weather Doppler device sends out radio waves. As the waves move out from the antenna, they come into contact with a number of objects in the air. When the radio waves hit bands of precipitation, such as rain, snow, or hail, they reflect back toward the radar station. Concentrations of other objects, such as dust or insects, will also appear on Doppler radar.
The weather Doppler picks up the reflections, which appear as images on the radar screen. If the object the radar has picked up is moving toward the weather Doppler, the waves are picked up at a higher frequency. Objects that are moving away from the Doppler radar appear at a lower frequency.
Part of the weather Doppler is a computer program that tells meteorologists about the speed and direction of winds. Changes in radar wave frequencies are used to make these calculations. The information taken from the images is used to predict the weather in a particular area.
Internet users can see weather Doppler images on various web sites online. They can see where bands of precipitation are present, with the image showing pockets of rain, snow and ice. The Doppler radar also indicates whether the precipitation is light, moderate or heavy. Members of the public can find out whether severe weather is moving toward where they live by checking out the Doppler radar images online.