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Phased Array Radar

Phased Array radar has a unique antenna that collects the same information as a conventional radar in about one-sixth the time. Researchers believe phased array could extend warning lead times from 10 minutes to 18-22 minutes. The radar's electronic beams can be directed independently at particular elements of a storm to give forecasters more accurate and complete data than the current NEXRAD radars. The new technology will also gather storm information not currently available, such as rapid changes in wind fields, to provide more thorough understanding of storm evolution. Researchers will be able to refine conceptual storm models and use that knowledge to evaluate and improve stormscale computer models. The phased array radar is expected to eventually replace the current network of WSR-88D radars. NSSL's National Weather Radar Testbed (NWRT) is the official facility where phased array technology will be tested and evaluated. PAR has the potential to provide revolutionary improvements in NWS tornado, severe storm, and flash flood warnings.

HOW DOES PHASED ARRAY WORK?

Current WSR-88D radars transmit one beam of energy at a time, listen for the returned energy, then mechanically tilts up a little higher, and samples another small section of the atmosphere. When it has sampled the entire volume of atmosphere, from bottom to top at a particular location, the radar goes back down, moves over a little, and starts the process over again. This continues until the radar has scanned the entire atmosphere, which takes around six or seven minutes. Phased arrays use multiple beams, sent out at one time, so the antennas never need to tilt. Scanning takes only 30 seconds, and it already has dual-polarization capabilities.

Schematic showing how the radar can span many targets at the same time and dwell on particular targets

The illustration shows from left: full-volume continuous scan through a developing cumulonimbus cloud, full-volume continuous scan through the planetary boundary layer (clear air) for mapping winds, detection and tracking of aircraft including non-cooperative targets, full-volume continuous scan through a supercell storm, and long-dwell scan through a region of a potential tornado.

ADVANTAGES OF PHASED ARRAY OVER WSR-88D

20 to 30-second volume scan rates, compared with 5-7 minutes with the WSR-88D
"Dwell" – the ability to repeatedly sample areas of interest
"Adaptive scanning" – the capability to quickly go back and look again at something that draws our attention, such as a severe weather feature
Lower failure rate

BROAD GOALS FOR PHASED ARRAY TECHNOLOGY

Demonstrate PAR technology can be applied to the tornado detection, forecast, and warning mission in a multi-use environment.
Demonstrate skill in probabilistic forecasts of tornadoes and other severe weather events using ensembles of models that assimilate PAR data
Determine if there is a viable economic strategy which would permit a national PAR network to support NOAA, DOT/FAA, DOD, Homeland Security and other national missions.

CURRENT RESEARCH PROJECTS

Demonstrate PAR technology can be applied to the tornado detection, forecast, and warning mission in a multi-use environment.
Demonstrate skill in probabilistic forecasts of tornadoes and other severe weather events using ensembles of models that assimilate PAR data
Determine if there is a viable economic strategy which would permit a national PAR network to support NOAA, DOT/FAA, DOD, Homeland Security and other national missions.

Remote PAR operations
One goal of the NWRT facility is to allow scientists at NSSL and across the nation to remotely operate the phased array radar to collect data in support of their research. A new Radar Control Interface (RCI) is being developed to simplify radar control and data collection operations.

Aircraft tracking processor
The PAR can perform several tasks at once – such as tracking aircraft and scanning weather. NSSL has been exploring the PAR aircraft tracking capabilities and found that the PAR aircraft tracks were consistent with data obtained from air traffic control reports for flights into and out of Will Rogers Airport in Oklahoma City, OK.

Beam multiplexing to improve scanning speed
Pulse compression
Electronic beam steering

THE BENEFITS OF PHASED ARRAY TECHNOLOGY

To meteorologists:

Local forecasters could have the latest artificial intelligence-based warning decision support systems at their fingertips
Tornado warnings could be issued up to 45 minutes in advance and in a graphical format instead of text

To hydrologists:

Improved lead time for flash flood warnings

To aviation:

Improved icing forecasts

To the public:

Increased tornado warning lead times
Timely and improved warnings of severe weather hazards

The SPY-1 Navy radar is being adapted for severe weather tracking

HISTORY OF PHASED ARRAY RADAR

Navy ships originally used AEGIS phased array radar (called SPY-1) technology to protect naval battle groups from missile threats. Researchers believe the same technology has great potential for increasing lead-time for tornado warnings.

In 2000, the U.S. Navy agreed to loan a phased array antenna to NSSL and provided the $10,000,000 in funding to help build the National Weather Radar Testbed (NWRT). The NWRT is a facility focused on developing faster and more accurate warning, analysis and forecast techniques for severe and hazardous weather using phased array and also upgraded WSR-88D radar technology. The National Weather Service provided the transmitter and the additional funding from NOAA, OU, Lockheed Martin, and OSRHE purchased the environmental processor. In addition, the FAA provided initial funding for research, program management and initial upgrades, and the NWS has donated equipment. The NWRT became operational in September 2003, the first data were collected in May, 2004, and data sets were collected during the 2005 storm season.

COLLABORATORS and PARTNERS

The National Weather Radar Testbed is a unique partnership among academia, industry, federal and state government agencies, and the Navy with a common goal of transforming military technology into a civilian research facility that will provide great benefit to the the nation.

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