How Do Radars Work?
Radar Technology for Weather & Climate
RADAR | RAdio Detection And Ranging
Radars are critical for understanding the weather; they allow us to “see” insideclouds and help us to observe what is really happening. Working together, engineers, technicians, and scientists collectively design, develop and operate the advancedtechnology of radars that are used to study the atmosphere.
What are Weather Radars?
Doppler weather radars are remote sensing instruments and are capable ofdetecting particle type (rain, snow, hail, insects, etc), intensity, and motion.Radar data can be used to determine the structure of storms and to help withpredicting severity of storms.
The Electromagnetic Spectrum
Energy is emitted in various frequencies and wavelengths from large wavelengthradio waves to shorter wavelength gamma rays. Radars emit microwaveenergy, a longer wavelength, highlighted in yellow.
How Do Radars Work?
The radar transmits a focused pulse of microwave energy (yup, just like amicrowave oven or a cell phone, but stronger) at an object, most likely acloud. Part of this beam of energy bounces back and is measured by the radar,providing information about the object. Radar can measure precipitation size,quantity, speed and direction of movement, within about 100 mile radius of itslocation.
How Does Doppler Radar Work?
Doppler radar is a specific type of radar that uses the Doppler effect to gather velocity data from the particles that are being measured. For example, a Doppler radar transmits a signal that gets reflected off raindrops within a storm. The reflected radar signal is measured by the radar's receiver with a change in frequency. That frequency shift is directly related to the motion of the raindrops.
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When a storm is stationary, the transmitted energy and the reflected energyor “echo” will not change, as shown below. | When a storm is moving towards the radar, the transmitted wavelength's frequency will be lower than the reflected wavelength frequency. | When a storm is moving away from the radar, the transmitted wavelength’s frequency will be higher than the reflected wavelength’sfrequency. |
Why does NCAR use radars for research?
Atmospheric scientists use different types of ground-based andaircraft-mounted radar to study weather and climate. Radar can be used tohelp study severe weather events such tornadoes and hurricanes, or long-termclimate processes in the atmosphere.
Ground-based Research Radar
The NCAR S-Band Dual-Polarization DopplerRadar (S-PolKa) is a 10-cm wavelength weatherradar initially designed and fielded by NCARin the 1990s. Continuously modified andimproved, this state-of-the-art radar system nowincludes dual-wavelength capability. When theKa-band is added, a 0.8-cm wavelength radar,it is known as S-PolKa. S-PolKa’s mission is topromote a better understanding of weatherand its causes and thereby ultimately provideimproved forecasting of severe storms, tornadoes, floods, hail, damaging winds,aircraft icing conditions, and heavy snow.
Airborne Research Radar
In the air, research aircraft can be outfitted with an array of radars. TheNCAR HIAPER Cloud Radar (HCR) can bemounted to the underside of the wing ofthe NSF/NCAR HIAPER research aircraft (amodified Gulfstream V jet) and delivers highquality observations of winds, precipitationand other particles. It was designedand manufactured by a collaborative teamof mechanical, electrical, aerospace, andsoftware engineers; research scientists; andinstrument makers from EOL.
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