Ideas for Teaching
Why Radar Can't (Usually) See Tornadoes
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Radar "Beamwidth"
A
traditional radar has a dish that both sends and receives pulses of electromagnetic
energy. Most radars can be aimed in many different directions. The WSR-88D
Doppler radars have fixed scanning patters.
The geometry of the dish and a few other factors help determine the pulse volume, which can be specified in degrees. Although the WSR-88D radar sends discrete pulses (and spends 99.57% of the time listening for return echoes) meteorologists like to use the convenient terms "beam" and "beamwidth" to describe where the radar is pointing and the effective resolution of the air being sampled.
We'll need the number(s) below for our calculations. Radar names are explained after the table.
| Radar Type | Effective Beamwidth (degrees) |
|---|---|
| WSR-88D | 1.0 |
| TDWR | 0.5 |
| DOW | 0.93 |
| SMART-Radar | 1.5 |
| typical TV station radar | 1-2 |
WSR-88D is the Doppler radar network used by the National Weather Service, Federal Aviation Administration, and Department of Defense.
TDWR is the Terminal Doppler Weather Radar, used around major airports in the US.
DOW refers to the Doppler on Wheels research radar at the University of Oklahoma.
SMART-Radar refers to the mobile research radars jointly owned and operated by the NOAA National Severe Storms Lab, Texas A&M, Texas Tech, and the University of Oklahoma.
TV station radars are made by several companies and the quality varies a great deal, in part by what the station wishes to spend on this equipment. TV stations also show WSR-88D data routinely but do not generally reveal the source of any particular radar image.
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Last updated: March
27, 2002
Created by: DSZ