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| NOAA Weather Radar (NEXRAD) | |
|---|---|
| Name | NOAA Weather Radar (NEXRAD) |
| Caption | WSR-88D Doppler radar antenna |
| Type | Weather radar network |
| Founded | 1988 |
| Operator | National Oceanic and Atmospheric Administration, National Weather Service |
| Headquarters | Silver Spring, Maryland |
NOAA Weather Radar (NEXRAD) NOAA Weather Radar (NEXRAD) is a continental network of Doppler weather radars operated by the National Weather Service and coordinated with the Federal Aviation Administration and the Department of Defense (United States). It provides mesoscale and synoptic-scale surveillance for severe convection, precipitation, and wind fields across the United States, supporting aviation, emergency management, and hydrology in real time. The system underpins operational forecasting at centers such as the National Centers for Environmental Prediction and research at institutions like NOAA laboratories and university atmospheric science departments.
NEXRAD consists of WSR-88D radars deployed to deliver reflectivity, radial velocity, and spectrum width data to users including the National Weather Service, Federal Aviation Administration, United States Air Force, United States Navy, FEMA, and state emergency management agencys. The network interfaces with forecasting centers such as the Storm Prediction Center, Weather Prediction Center, and local National Weather Service Forecast Officees, as well as research facilities like the National Severe Storms Laboratory and universities including University of Oklahoma and Texas A&M University. Operational products feed into systems run by NOAA Weather Radio, Air Traffic Control, and international partners such as Environment Canada and Met Office.
Development began after severe weather events motivated modernization initiatives involving agencies including the National Science Foundation, the United States Congress, and the Office of Management and Budget. The WSR-88D program was a collaboration among contractors and research partners such as Raytheon Company, ITT Corporation, and the MIT Lincoln Laboratory. Early deployment in the late 1980s and 1990s replaced legacy C-band radars used by the National Weather Service and incorporated advances from projects at the Cooperative Institute for Mesoscale Meteorological Studies and NOAA Research Laboratories. Upgrades over decades included dual-polarization delivered during programs coordinated with NASA and funded by appropriations from the United States Senate and United States House of Representatives.
The WSR-88D is an S-band, 10 cm wavelength Doppler radar with a 3.5° horizontal beamwidth and a parabolic antenna roughly 8.5 m in diameter produced by contractors like ITT and Unisys. It uses pulse-Doppler processing to measure reflectivity, mean radial velocity, and spectrum width and later added dual-polarization parameters including differential reflectivity and correlation coefficient through upgrades influenced by research at NOAA National Severe Storms Laboratory and University of Massachusetts Amherst. Antenna rotation rates, pulse repetition frequency, and volume coverage patterns are managed to balance range resolution and temporal update rates, as coordinated with agencies including the Federal Emergency Management Agency and operators like the United States Air Force Weather Agency.
NEXRAD provides base data (reflectivity, velocity, spectrum width) and derived products such as composite reflectivity, echo tops, storm-relative velocity, mesocyclone detection, and hydrometeor classification. Processing pipelines at the National Centers for Environmental Prediction and local forecast offices use algorithms developed in collaboration with research entities including National Severe Storms Laboratory, Cooperative Institute for Research in the Atmosphere, and universities like Colorado State University and Penn State University. Products integrate into nowcasting systems like NEXRAD Level II/III distribution, display platforms used by AccuWeather and media organizations, and decision support tools for NOAA Weather Radio and Air Traffic Control.
The network comprises approximately 160 WSR-88D sites sited to provide overlapping coverage across the continental United States, Alaska, Hawaii, and select offshore areas, coordinated with FAA radar assets and military radars. Data flow uses redundant communications backbones including dedicated circuits, satellite links, and internet protocols managed by National Oceanic and Atmospheric Administration information technology branches and regional National Weather Service networks. Centralized ingest centers at agencies like National Centers for Environmental Prediction perform quality control and distribution to partners such as NOAA National Environmental Satellite, Data, and Information Service, Department of Defense, and state emergency operations centers.
Operational meteorology applications include severe thunderstorm and tornado warning issuance by the National Weather Service, precipitation estimation for hydrologic modeling used by the United States Geological Survey and flood control districts, and aviation hazard detection by the Federal Aviation Administration. Research uses extend to convective storm dynamics at institutions like National Severe Storms Laboratory, climate studies at NOAA National Centers for Environmental Information, and algorithm development at universities including University of Illinois Urbana-Champaign and University of Wisconsin–Madison. Other users include broadcast media such as The Weather Channel, private meteorological services like Weather Company, emergency managers at Federal Emergency Management Agency, and transportation agencies including Federal Highway Administration.
Limitations include beam blockage and ground clutter in complex terrain such as the Appalachian Mountains and Sierra Nevada (U.S.), attenuation in heavy precipitation, and range-folding ambiguities at long distances from sites including those near Gulf of Mexico coasts. Aging hardware and the need for sustained funding from entities such as the United States Congress pose modernization challenges; mitigation efforts involve partnerships with research agencies like NASA, National Science Foundation, and private firms. Ongoing issues include data latency, network resilience during disasters affecting infrastructures overseen by Federal Communications Commission, and integration with emerging systems such as phased-array prototypes tested by Office of the Secretary of Defense and academic consortia.
Category:Weather radar