Wednesday, April 29, 2009
Doppler Detected Speeders!
There's some good radar refraction taking place from the Memphis radar site this evening. Meteorologist Phil Baker at the NWS pointed it out to me and I captured some images on StormTRACK Doppler 8. Look at the "blips" just north of Blytheville on I-55. That's not rain. That's traffic!
Radar does not operate like a laser beam in a straight line, but it bends vertically and horizontally and speeds up and down in response to the atmospheric conditions. (I believe the air density is the main driver to this phenomenon.) When the wavelength is slower in spots, it tends to bend toward the slower portion of the wave. This is called refraction. When it does this, you can occationally see traffic on the interstate!
The second image below shows the "velocity scope". we typically use it to detect rotation. If you notice the bright pink areas, that's the traffic. Phil says he clocked some people going 82 mph... LOL I wonder if the NWS can write tickets? :)