Weather Radar Technology Beyond NEXRAD (2002)
Chapter: Appendix A: NEXRAD WSR-88D System Characteristics
APPENDIX A
NEXRAD WSR-88D System Characteristics
|
Parameter/Feature |
Value/Description |
|
Radar System |
|
|
Range of observation |
|
|
Reflectivity |
460km |
|
Velocity |
230km |
|
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-ft) 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 |
11.89m (39 ft.) |
|
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 |
|
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; log output |
|
Dynamic range |
95 dB max; 93 dB at 1 dB compression |
|
Minimum detectable signal |
-113 dBm |
|
Noise temperature |
450 K |
|
Intermediate frequency |
57.6 MHz |
|
Sampling rate |
600 kHz |
|
Signal Processor |
|
|
Type |
Hardwired/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 |
Digital, infinite impulse response (IIR), 5-pole |
|
Clutter suppression |
30–50 dB |
|
Filter notch half-width |
0.5–4 m s-1 |
|
Radar Product Generator (RPG) |
|
|
RPG processor |
32-bit general purpose digital computer |
|
Shared memory |
32-MB semiconductor memory, expandable to 96 MB |
|
Wide band communication |
1.544 Mbits s-1 data rate |
|
Narrow band communication |
Up to 21 of 9,600/4,800 bits s-1 4-wire Up to 26 of 9,600/4,800 bits s-1 2-wire (will have 14,400/9,600/4,800 bits s-1 capability) |
|
RPG Graphic Display Processor |
|
|
Principal user processor (PUP) |
Fixed point: 32-bit general purpose digital computer |
|
Communications |
9600/488 bits s-1; 2- and 4-wire (maximum: 10 lines) RS449/RS2332 converters |
|
Video |
Color, with split-screen and zoom features |
|
Mass storage |
Up to two 600 MB disks |
|
Other |
|
|
National Climatic Data Center (NCDC) |
National archive for NEXRAD data and other meteorological and climatological data. |
|
Level II archive |
Interface located at the Radar Data Acquisition (RDA). Digital base data output from the signal processor that includes base reflectivity, mean radial velocity, and spectrum width. Other data include information on synchronization, calibration, date, time, antenna position, and operational mode. Recorded on 8-mm magnetic tape and sent to NCDC for permanent storage. |
|
Level III archive |
Interface is located at the Radar Product Generator (RPG). A set of pre-determined products defined in FMH-11 Part A. Data are archived on WORM Optical Disk and sent to NCDC for permanent storage. |
|
National Weather Radar Network |
Consists of WSR-88D sites dispersed throughout the conterminous United States plus Department of Defense sites or non-CONUS Department of Transportation sites. |
