Doppler radar can be divided into several different categories according to the wavelength of the radar. The different bands are L,S,C,X,K. The names of the radars originate from the days of WWII.
L band radars operate on a wavelength of 15-30 cm and a frequency of 1-2 GHz. L band radars are mostly used for clear air turbulence studies.
S band radars operate on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated. This makes them useful for near and far range weather observation. The National Weather Service (NWS) uses S band radars on a wavelength of just over 10 cm. The drawback to this band of radar is that it requires a large antenna dish and a large motor to power it. It is not uncommon for a S band dish to exceed 25 feet in size.
C band radars operate on a wavelength of 4-8 cm and a
frequency of 4-8 GHz. Because of the wavelength and frequency, the dish size
does not need to be very large. This makes C band radars affordable for TV
stations. The signal is more easily attenuated, so this type of radar is best
used for short range weather observation. Also, due to the small size of the
radar, it can therefore be portable like the University of Oklahoma's Doppler
on Wheels. (DOW) The frequency allows C band radars to create a smaller beam
width using a smaller dish.
C band radars also do not require as much power as an S band radar. The NWS transmits at 750,000 watts of power for their S band, where as a private TV station such as KCCI-TV in Des Moines only broadcasts at 270,000 watts of power with their C band radar.
X band radars operate on a wavelength of 2.5-4 cm and a frequency of 8-12 GHz. Because of the smaller wavelength, the X band radar is more sensitive and can detect smaller particles. These radars are used for studies on cloud development because they can detect the tiny water particles and also used to detect light precipitation such as snow.. X band radars also attenuate very easily, so they are used for only very short range weather observation. Most major airplanes are equipped with an X band radar to pick up turbulence and other weather phenomenon. This band is also shared with some police speed radars and some space radars.
K band radars operate on a wavelength of .75-1.2 cm or 1.7-2.5 cm and a corresponding frequency of 27-40 GHz and 12-18 GHz. This band is split down the middle due to a strong absorption line in water vapor. This band is similar to the X band but is just more sensitive. This band also shares space with police radars.
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by Adam Frederick, firstname.lastname@example.org
Content and Images (unless otherwise noted) Copyright 1999 Adam Frederick
Last updated 07/22/99 10:50 AM