. "Appendix B: Characteristics of the NEXRAD Radar." Flash Flood Forecasting Over Complex Terrain: With an Assessment of the Sulphur Mountain NEXRAD in Southern California. Washington, DC: The National Academies Press, 2005.
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Flash Flood Forecasting Over Complex Terrain: With an Assessment of the Sulphur Mountain NEXRAD in Southern California
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Flash Flood Forecasting Over Complex Terrain: With an Assessment of the Sulphur Mountain NEXRAD in Southern California
Appendix B
Characteristics of the NEXRAD Radar
Parameter or Feature
Value or Description
Radar System
Range of Observation
Reflectivity
460 km
Velocity
230 km
Angular Coverage
Azimuth
Full circle or sector
Elevation
Operational limits; –1° to +20°
Antenna
Type
S-band, center-fed, parabolic dish
Reflector aperture
8.54-m (28-foot) diameter; circular
Beamwidth (one-way, 3 dB)
0.96° at 2.7 GHz; 0.88° at 3.0 GHz
Gain
45.8 dB at 2.85 GHz (midband)
Polarization
Linear horizontal
First side-lobe level
–29 dB
Steerability
360° azimuth; –1° to +45° elevation
Mechanical limits
–1° to +60°
Rotation rate
30° s –1 (azimuth and elevation)
Angular acceleration
15° s –2 (azimuth and elevation)
Pointing accuracy
±0.2°
Radome
Type
Fiberglass skin foam sandwich
Diameter
11.89 m (39 feet.)
RF Loss (two-way)
0.3 ± 0.06 dB over 2.7–3.0-GHz band
Transmitter
Type
Master Oscillator Power Amplifier (MOPA)
Frequency range
2.7–3.0 GHz
Peak power output (nominal)
500 kW into antenna
Pulsewidth (nominal)
1.57 μs (short pulse); 4.5 μs (long pulse) ± 4%
RF duty cycle (maximum)
0.002
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Flash Flood Forecasting Over Complex Terrain: With an Assessment of the Sulphur Mountain NEXRAD in Southern California
Pulse Repetition Frequency
Long pulse
322–422 Hz ± 1.7%
Short pulse
322–1282 Hz ± 1.7%
Waveform types
Contiguous and batch (phase-coded build 8.0)
Receiver
Type
Linear
Tunability (frequency range)
2.7–3.0 GHz
Bandwidth (3 dB)
0.63 MHz (short pulse); 0.22 MHz (long pulse)
Phase control
Selectable
Receiver channels
Linear output I/Q
Dynamic range
95 dB max; 93 dB at 1-dB compression
Minimum detectable signal
–113 dBm (ORDA)
Noise temperature
450 K (ORDA)
Intermediate frequency
57.6 MHz
Sampling rate
600 kHz (This remains the same for the I/Q samples; IF samples will be at 72 MHz)
Signal Processor
Type
Programmable
Parameters derived
Reflectivity; mean radial velocity; Doppler spectral width
Algorithms (respective)
Power averaging; pulse-pair; single-lag correlation
Accuracy (Standard Deviation)
Reflectivity
<1 dB
Velocity and spectrum width
<1 m s–1
Number of Pulses Averaged
Reflectivity
6–64
Velocity and spectrum width
40–200
Range Resolution
Reflectivity
1 km
Velocity and spectrum width
0.25 km
Azimuth Resolution
Reflectivity
1°
Velocity and spectrum width
1°
Clutter canceller
Gaussian Model Adaptive Processing Filter, Spectral Domain
Clutter suppression
30–50 dB max
Radar Product Generator (RPG)
RPG processor
64-bit reduced instruction set (RISC) digital computer
Shared memory
512-MB semiconductor memory
Wide-band communication
1.544 Mbit s–1 data rate
Narrow-band communication
Up to 13 of 14,400/4,800 bit s–1 4-wire
(1 may be 33,600 bit s–1 capable)
8 of 14,400/4,800 bit s–1 2-wire
Up to 9 Wide Area Network (WAN) connections
RPG Graphic Display Processor
Principal user processor (PUP)
64-bit RISC digital computer
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Flash Flood Forecasting Over Complex Terrain: With an Assessment of the Sulphur Mountain NEXRAD in Southern California
Communications
14,400/4,800 bit s–1; 2- and 4-wire (maximum: 28 lines)
Video
Color, with split-screen and zoom features
Mass
storage Up to two 40-GB disks
Other
National Climatic Data Center (NCDC)
National archive for NEXRAD data and other meteorological and climatological data.
Level II archive
Network interface located at the RPG. Digital base data are output from the Base Data Dissemination System (BDDS), which includes base reflectivity, mean radial velocity, and spectrum width. Data are sent electronically to the NCDC for permanent storage. (Completed nationwide in September 2004)
Level III archive
Interface is located at the RPG. A set of predetermined products defined in FMH-11 Part A is sent electronically to NCDC for permanent storage. (Completed nationwide in September 2004)
National Weather Radar Network
Consists of WSR-88D sites dispersed throughout the conterminous United States (CONUS) plus Department of Defense sites or non-CONUS Department of Transportation sites.
