Phased Array Radar
Kristina Kiest
/ Categories: WPO News

Phased Array Radar

Research Informed Decision-Support for the Future of Weather Forecasting.

Radar is an essential observing technology for weather forecasting and research. It provides critical data for weather forecasts and warnings, benefits meteorological research and aids the National Weather Service’s (NWS) delivery of impact-based decision support services to partners. This includes those in the emergency management and water resources communities, and federal, state, local, tribal, and territorial government partners. NOAA’s National Weather Service is part of a tri-agency partnership with the United States Air Force and Federal Aviation Administration to support our Nation’s weather radars. The combined current system is the Weather Surveillance Radar 1988-Doppler system (WSR-88D), also known as NEXtgeneration RADar (NEXRAD), with 159 operational stations across the country and U.S. territories. The WSR-88D network has been in operation since the early to mid 1990s, but has been continuously upgraded with the latest technology. NEXRAD is the primary observing system that collects data for weather prediction, including winds, precipitation data, turbulence, lightning, and other environmental variables. Combining this data with forecast models, the NWS is able to provide daily forecasts that are critical for public needs, including warnings and watches for severe storms, tornadoes, hurricanes, flooding, and heavy snow. 

The NEXRAD Service Life Extension

While many of NEXRADs components have been continually upgraded with the latest technology over the past 25 years, a few major components are original to the system. Because of this, a Service Life Extension Program (SLEP) was initiated in 2015 to repair and refurbish these major components such as the signal processor, transmitter, pedestal, shelters, and generators. This work will be completed in 2024 and will ensure NEXRAD remains operational until at least 2035. Meanwhile, NOAA is exploring options for NEXRAD beyond 2040. This could include another Service Life Extension Program, a rotating dish replacement system, or Phased Array Radar.

Phased Array Radar Promises the Future of Forecasting 

Over the past 20 years NOAA/OAR,  industry, and academia have made significant advancements on Phased Array Radar (PAR) research, development, and technology for weather surveillance and other applications. Because of these advancements, PAR is a leading contender in the solution for replacing the legacy system. PAR provides rapid, flexible scanning techniques and can complete a 90-degree sector scan of the atmosphere in about 60 seconds. This is a significant improvement over the current operational system, which takes 4-5 minutes to scan the same volume. The result is a more precise representation of rapidly evolving severe weather phenomena for forecasters to better sense atmospheric conditions and issue more accurate and timely warnings. PAR-enabled volume coverage patterns allow for low-level wind observations and can provide a top-to-bottom profile of storms about once per minute, which allow for a better model analysis of storm spin-up and a more accurate assimilation of wind data for factors such as updraft forcing, size, strength, and the storm track. These technical improvements may offer significant advancements in forecast accuracy on shorter timescales for acute extreme weather, such as tornadoes, severe weather, and flash flooding. This information is critical for aviation, transportation sectors, and emergency management. 

PAR uses an integrated, flat antenna which contains an array of thousands of individual elements that scan electronically, rather than mechanically, so the radar can re-scan areas very quickly and adapt to different scenarios (such as targeted scanning during severe weather). This switch to array technology versus dish technology also has the potential to allow engineers and technicians to isolate and maintain radar components without taking the entire system offline, which may reduce maintenance downtime.

Research and Science-Informed Decision Support with the Weather Program Office 

A careful evaluation of PAR technology and other alternatives is underway to determine the future of NOAA’s weather radar. As part of that evaluation, the Weather Program Office, in collaboration with the National Severe Storms Laboratory (NSSL) will deliver to the NWS timely, state-of-the-science information to inform their decision-making process for the next operational weather radar system. This includes information on PAR weather surveillance technology and an understanding of the criteria needed to transition PAR technology to operations. The National Weather Service will use this information to make a determination on the future of NEXRAD by 2030, with a target date of implementing a radar follow-on plan by 2040 that helps improve operational weather forecasting with better, more accurate weather warnings to reduce loss of life and property damage. 

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