Radars. Sandra Cruz-Pol Professor Electrical and Computer Engineering Department University of Puerto Rico at Mayagüez CASA- C ollaborative A daptive S ensing of the A tmosphere 2006. What is a Radar? Ra dio d etection a nd r anging. How does a radar work? Radar Concepts Games.
Electrical and Computer Engineering Department
University of Puerto Rico at Mayagüez
CASA- Collaborative Adaptive Sensing of the Atmosphere
The frequency of the em wave used depends on the application. Some frequencies travel through clouds with virtually no attenuation.
ALL em waves move at the speed of light
How does a radar work?
Compare to: Acoustic Echo-location
t = 2 x range / speed of sound
Example:range= 150 m
Speed of sound≈340 meters/second
t= 2 X 150 / 340 ≈ 1 second
t = 2 x range / speed of light
measure t, then determine Range
Example:t = .001 sec
Speed of light = c = 3x108 meters/second
Range = .001 x 3x108 / 2 = 150,000 m = 150 km
Scattered wave amplitude
conveys size of the scattering objects. Measure amplitude, determine size.
Closer look at Large drop
Transmitted Pulse #1
In summary, radars work by…
Transmitting microwave pulses….
and measuring the …
… of the microwave echo in each range gate
Other concepts of Radars
Hurricane Andrew, 1992
QPE – Quantitative Precipitation Estimation
NEXRAD System Today
May 3, 1999 Tornado Outbreak in Oklahoma
Water spout at Mayaguez Beach, PR- Sept 2005 –unseen by NEXRAD
D is the antenna diameter
λ is the wavelength of signal in air
Small wavelengths (high frequencies) = small antennas
But small wavelengths attenuate more
How wide and tall are various things we want to see?
Width of Meteorological Objects (i.e. Storms, Tornadoes)
Fill in the table with values you calculate
Play related games