radar palet e home radar systems analysis & diagnosis 1 radar systems where are the radars...
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Analysis & Diagnosis 1Radar Palette Home Radar Systems
Radar Systems
• Where are the radars located?• What is the radar coverage?• What are some of the characteristics that
differentiate between radar systems?• Radar Scan strategies?• Radar products?
Analysis & Diagnosis 2Radar Palette Home Radar Systems
Radar History – in Brief
• Radar Radio Detection And Ranging • In 1887, a physicist named Heinrich Hertz began
experimenting with radio waves in his laboratory in Germany.
• Sir Robert Alexander Watson-Watt (1892--1973)Watson-Watt was the Scottish physicist who developed the radar locating of aircraft in England.
• Radar was patented (British patent) in April, 1935. • Doppler RADAR is named after Christian Andreas
Doppler, an Austrian physicist who first described in 1842, how the observed frequency of light and sound waves was affected by the relative motion of the source and the detector. This phenomenon became known as the Doppler effect.
• Weather radar. started in 1943 as a Canadian Army project in Ottawa
Analysis & Diagnosis 3Radar Palette Home Radar Systems
The distribution of stations after implementation
DND ConventionalNew Doppler
Existing Doppler
Dopplerized/Relocated
U.S. Doppler
DND Doppler
Dopplerized DND
The radar network in 2003.
Analysis & Diagnosis 4Radar Palette Home Radar Systems
North American Radar Coverage
Analysis & Diagnosis 5Radar Palette Home Radar Systems
Canadian Radar Coverage – Canadian Composite
For the masses….
Analysis & Diagnosis 6Radar Palette Home Radar Systems
Nominal Radar Coverage with 256 km range
However, in winter …
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Effective Radar Coverage with 2 km echo tops
Large blind swaths across the country
Even here on the 401
♫ I’m dreaming of gap-filling X-band network …
Analysis & Diagnosis 8Radar Palette Home Radar Systems
Pacific Network
Analysis & Diagnosis 9Radar Palette Home Radar Systems
Prairie Network
Analysis & Diagnosis 10Radar Palette Home Radar Systems
Ontario Network
Analysis & Diagnosis 11Radar Palette Home Radar Systems
Quebec Network
Analysis & Diagnosis 12Radar Palette Home Radar Systems
Atlantic Network
Analysis & Diagnosis 13Radar Palette Home Radar Systems
Radar Data in Ontario
Analysis & Diagnosis 14Radar Palette Home Radar Systems
NWS Radar Composite
Meteorologists without Borders
Analysis & Diagnosis 15Radar Palette Home Radar Systems
Antenna Scan Strategies
• Conventional: – 24 PPI scans– top down– 6 RPM– 24.6 to 0.3 degrees (0.1 in
winter)– 5 minutes to complete– 10 seconds per elevation
angle, 6 per minute
• Doppler:– 3 scan angles– bottom up ?– much slower (0.85 RPM)
since more sample points are collected for the Doppler processing
– fills much of remaining 5 minutes
10 minute cycle
Analysis & Diagnosis 16Radar Palette Home Radar Systems
Some basic radar products CAPPI vs. PRECIP
• CAPPI 1.0– Uses conventional reflectivity scans
– 1 km AGL out to 100 km, then rides up the lowest PPI angle (~0.1° winter & 0.3 ° summer) out to 256 km
– Precipitation is relatively high above ground and can grow considerably between 1 km AGL and the surface
• PRECIP– Uses long range doppler reflectivity scan within 125 km of radar, including
ground clutter removal
– Uses lowest PPI conventional reflectivity scan beyond 125 km of radar
– Doppler reflectivity not quite as sensitive to weak echoes
– Best product for seeing precipitation close to ground
– Therefore, Precipitation Accums (PA) from PRECIP product should be better than from CAPPI, as long as ground doesn’t absorb too much beam power
Analysis & Diagnosis 17Radar Palette Home Radar Systems
Some basic radar products
CAPPI 1.0 km vs. PRECIP product
range (km)
beam
heigh
t (km
)
2 2
1010
1818
0.0 00.0 0
2.0 02.0 0
25.0 025.0 0
CAPPI 1.0PRECIP
Doppler reflectivity Conventional reflectivity
Analysis & Diagnosis 18Radar Palette Home Radar Systems
PRECIP product example
Boundary between doppler & conventional reflectivity scans
Analysis & Diagnosis 19Radar Palette Home Radar Systems
Gain vs Beamwidth
• The smaller the beamwidth, better the gain• Improved gain means higher signal strength for
distant objects or small targets– e.g. light precipitation may be detected at greater
distances
Analysis & Diagnosis 20Radar Palette Home Radar Systems
Weather Radar Bands
• The more common weather radar wavelengths and letter designations are:
BAND (cm) EXAMPLE S 10 NEXRAD,
MCGILL C 5 NRP, EUROPE
X 3 U OF TORONTO, MCGILL
Analysis & Diagnosis 21Radar Palette Home Radar Systems
Pulse Repetition Frequency (PRF)
• The pulse repetition frequency (PRF) is the number of pulses emitted by the radar per second (pps)
• A pulse travelling to a target at range rmax and back will cover a distance 2rmax
• The pulse will make it back to the radar before the next pulse is emitted if:
2rmax=c/PRF
Analysis & Diagnosis 22Radar Palette Home Radar Systems
PRF and radar range
• Thus, the higher the PRF, the lower the effective range (ignoring second-trip echos from objects located beyond rmax)
• The lower the PRF, the higher the range.
rmax=c/2PRFOr….
Analysis & Diagnosis 23Radar Palette Home Radar Systems
Rmax vs PRF
0
100
200
300
400
500
600
700
PRF
R m
ax (
km)
Analysis & Diagnosis 24Radar Palette Home Radar Systems
Rmax in selected modes
Mode PRF Rmax (km)
Reflectivity 250 600
Doppler 900 & 1200
125
Clear Air 50 3000
The Clear Air PRF is 50 allowing greater range.
Analysis & Diagnosis 25Radar Palette Home Radar Systems
CONVENTIONAL RADAR DISPLAYS•PPI
•CAPPI
•FOUR CAPPI
•MAX R
•ECHO TOP
•SEVERE WEATHER
•CROSS SECTION STYLE:
-DIAMETER CROSS SECTION
-ARBITRARY CROSS SECTION
Analysis & Diagnosis 26Radar Palette Home Radar Systems
PPI Elevations and Angles
Analysis & Diagnosis 27Radar Palette Home Radar Systems
Radar beam height vs. range
Height of radar beam in normal atmospheric conditions
range (km)
beam
heigh
t (km
)
2 2
1010
1818
0.0 00.0 0
2.0 02.0 0
25.0 025.0 0
1.00 beam
Beam widens with range
Overshoots low tops
Cone of silence
Analysis & Diagnosis 28Radar Palette Home Radar Systems
PPI Display - 0.3 Degree Angle
Analysis & Diagnosis 29Radar Palette Home Radar Systems
PPI and CAPPI
1.5km CAPPI
4.0 km CAPPI
0.3 Degree PPI
0.3 Degree PPI
Analysis & Diagnosis 30Radar Palette Home Radar Systems
CAPPI
Analysis & Diagnosis 31Radar Palette Home Radar Systems
Cross-sections - CAPPI - Echo Top
Analysis & Diagnosis 32Radar Palette Home Radar Systems
MAXR Data Display
Analysis & Diagnosis 33Radar Palette Home Radar Systems
Severe Weather Display