Flash Flood Forecasting Over Complex Terrain: With an Assessment of the Sulphur Mountain NEXRAD in Southern California (2005)
Chapter: Appendix B: Characteristics of the NEXRAD Radar
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 |
|
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 |
|
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. |
