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WSR-88D
The WSR-88D (NEXRAD) system is a network of over 150 Doppler weather radars jointly developed and operated by the NWS, the DOD, and the FAA. NSSL is engaged in a project to continually evolve the WSR-88D system, taking full advantage of advances in science and technology to improve forecasts and warnings of hazardous weather.
IDENTIFYING PROBLEMS AND FINDING SOLUTIONS:
Homeland Security
PROBLEM: Unsecured airspace: Unsecured airspace due to lack of Federal Aviation Administration (FAA) radar coverage or FAA radars not continuously in operation leave vulnerable gaps in our homeland security.
SOLUTION: Using WSR-88D to track, classify and identify aircraft: Airplane signatures are easy to see and filter in weather radar data. Since the network of WSR-88D radars in the U.S. is comprehensive and always in operation, NSSL is working to develop the capability to track and identify unfriendly aircraft, using WSR-88D data, when the pilot is not responding. By studying the radar spectral signatures of aircraft, NSSL has learned that weather radar can be used to identify different sizes and even different kinds of airplanes, including large or small aircraft or those with, or without a propeller. This important homeland security benefit will help secure airspace not under the FAA's Air Traffic Control System Command Center.
Forecast and Warning Improvements
PROBLEM: WSR-88D is limited to the radial component of the wind field
SOLUTION: Techniques to "read between the lines" of Doppler velocity data provide additional information about the environment, including developing tornadoes.
Radar Improvements
PROBLEM: A need for better, cleaner, faster WSR-88D signal processing
SOLUTION: Techniques to improve signal processing are tested and evaluated at NSSL before being deployed on NWS systems.
SUCCESSES: Mitigation
of range and velocity ambiguities 
:
Conventional radars have range and Doppler velocity ambiguity problems that
are connected. Trying to alleviate one worsens the other. Two techniques have
emerged as viable candidates to address these issues: systematic phase coding
and staggered pulse repetition time (PRT). The two techniques are complementary
since they offer advantages at specific elevation angles, and can be simultaneously
incorporated into the same volume coverage pattern.
An algorithm (SZ-2) for the initial deployment of range and velocity ambiguity mitigation techniques on the RDA subsystem has been developed. SZ-2 will replace the Doppler half of split cuts at the lowest elevation angles of the antenna beam.
WHAT'S NEXT: Research continues for SZ phase coding and the staggered PRT technique. Both algorithms have been refined to meet WSR-88D operational requirements and tested on data collected with the KOUN radar.
A novel staggered PRT spectral processing technique was developed. This, in conjunction with the ground clutter filter for staggered pulse developed in previous years, makes the staggered PRT technique a viable candidate to replace the legacy Batch mode at intermediate elevation angles.
