Radar Principles Flashcards
Types of Radar Deployments
Airborne, Space, Mobile, NEXRAD
K-band
Wavelength 0.75-1.2cm, 1.7-2.5cm and frequencies of 27-40 GHz and 12-18 GHz (Police/radar guns)
X-band
Wavelength 2.4-4 cm and frequency 8-12 GHz (aircraft weather avoidance radars, DOW)
C-band
Wavelength 4-8 cm and frequency 4-8 GHz (former NWS local warning radars; TV stations)
S-band
Wavelength 8–15 cm frequency 2-4 GHz (NWS NEXRAD, WSR-88D Doppler weather surveillance radar requires antenna dish 25-30 ft diameter; ATC ASR radars)
L-band
Wavelength 15-30 cm and frequency 1-2 GHz (air traffic control ARSR radars; clear air turbulence studies)
Microwave oven E-M radiation is ~2450 MHz frequency and the wavelength is about 12cm (~4.7in) which is very similar to _______
Weather radar surveillance operations
E-M Microwave radiation emitted by ________ and ________ is __________
Weather radars, home microwave ovens, Non ionizing radiation
rearrange DNA and other cellular structures
Ionizing radiation
Does not rearrange DNA and other cellular structures
Non-ionizing radiation
The _______ (shorter) the ______ the _____ (smaller) the precip-size particle that can be detected
Longer, wavelength, larger
The ______(shorter) the _______, the ____(more) likely that precip attenuation of the radar signal will occur
Longer, wavelength, less,
The _______(shorter) the ________ the _______(smaller) the diameter of the radar antenna/dish is required; this has major implications for onboard aircraft ______________
Longer, wavelength, larger, rather-avoidance radars
The NOAA National Weather Service WSR-88D Doppler radar is a ___________ (s-band) weather detection radar that is excellent at sampling most precip particles without encountering any __________ due to precip attenuation
10-cm wavelength, significant signal loss
A large amount of horizontally polarized EM energy is transmitted but only a ______ of energy is reflected back to the radar receiver,
Fraction
Range-Height Information (RHI) assume ________
Standard refractivity index
Power returned to the radar by a target is ______ related to the ___________ Z, and _______ related to the ______ R.
Directly, reflectivity factor, inversely, range
Only a _____ increase in drop diameter can result in a ______ increase in reflectivity Z
Small, large
Large drops return ______ power….. but can contribute ______ to total water mass
Most, less
One 1/4 inch diameter drop returns as much energy as ________ of 1/8 inch diameter
64 drops
However, one 1/4 inch diameter drop has a volume of only 0.065in^3, where as 64 1/8inch diameter drops yield a volume of 0.52 in^3 or __________ total water mass
8 times as much
The one 3mm diameter rain drop returns _______ and produces a larger reflectivity than the 64 1mm drops do….. yet the one 3mm diameter rain drop contains ______ total water mass than the 64 1mm rain drops
More power, much less
Since we don’t know the _____ distribution of ______ particles we can use the ________ (sintead of reflectivity), which is a function of the power returned and the range/distance from the radar
Actual, precipitation, equivalent reflectivity
A Doppler weather measures a single component of motion, but only ______ or _____ from the radar
Toward, away
Typical rain drop is a ‘flat’ oblate spheroid with a ______ horizontal _____ that returns more energy in the horizontal plane
Wider, axis
Dual-polarized radar provides better z-r relationship and rainfall estimates by determining _________
Precipitation type
Values of Zdr well ______ indicate the hydrometeors in the volume are ________ (rain) meaning their horizontal axis is longer than their vertical axis
Above zero, horizontally oriented
Values of Zdr well ______ indicate the hydrometeors in the volume are ________ (large hail) meaning their vertical axis is longer than their horizontal axis
Below zero, vertically oriented
Values of Zdr ______ indicate hydrometeors in the volume have nearly ________ (snow, giant hail) in the mean
Near zero, spherical shape
Zar values for meteorological echos typically range between _____ dB and _____ dB
-2, 6
Power returned to the radar is ________ to the power transmitted and the target reflectivity
Directly related
Power returned to the radar is _______ to the target range
Indirectly relates
Radar ______ increases with increasing ________
Beam height, range
WSR-88D Doppler weather radar 4-bin-average (4BA) Doppler velocity data _______ as reconnaissance aircraft flight-level wind speed data
Is as accurate
Zero greater than or equal to 2 is
Rain
Zdr less than or equal to 0 is
Hail/graupel
