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Weather Radar Technology Beyond NEXRAD (2002)

Chapter: Appendix A: NEXRAD WSR-88D System Characteristics

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Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
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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°

Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×

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

Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×

Range Resolution

Reflectivity

1 km

Velocity and spectrum width

0.25 km

Azimuth Resolution

Reflectivity

Velocity and spectrum width

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.

Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×

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.

Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×
Page 69
Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×
Page 70
Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×
Page 71
Suggested Citation:"Appendix A: NEXRAD WSR-88D System Characteristics." National Research Council. 2002. Weather Radar Technology Beyond NEXRAD. Washington, DC: The National Academies Press. doi: 10.17226/10394.
×
Page 72
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Weather radar is a vital instrument for observing the atmosphere to help provide weather forecasts and issue weather warnings to the public. The current Next Generation Weather Radar (NEXRAD) system provides Doppler radar coverage to most regions of the United States (NRC, 1995). This network was designed in the mid 1980s and deployed in the 1990s as part of the National Weather Service (NWS) modernization (NRC, 1999). Since the initial design phase of the NEXRAD program, considerable advances have been made in radar technologies and in the use of weather radar for monitoring and prediction. The development of new technologies provides the motivation for appraising the status of the current weather radar system and identifying the most promising approaches for the development of its eventual replacement.

The charge to the committee was to determine the state of knowledge regarding ground-based weather surveillance radar technology and identify the most promising approaches for the design of the replacement for the present Doppler Weather Radar. This report presents a first look at potential approaches for future upgrades to or replacements of the current weather radar system. The need, and schedule, for replacing the current system has not been established, but the committee used the briefings and deliberations to assess how the current system satisfies the current and emerging needs of the operational and research communities and identified potential system upgrades for providing improved weather forecasts and warnings. The time scale for any total replacement of the system (20- to 30-year time horizon) precluded detailed investigation of the designs and cost structures associated with any new weather radar system. The committee instead noted technologies that could provide improvements over the capabilities of the evolving NEXRAD system and recommends more detailed investigation and evaluation of several of these technologies. In the course of its deliberations, the committee developed a sense that the processes by which the eventual replacement radar system is developed and deployed could be as significant as the specific technologies adopted. Consequently, some of the committee's recommendations deal with such procedural issues.

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