Significant Paper: The Impact of Range Oversampling Processing on Tornado Velocity Signatures Obtained from WSR-88D Super-Resolution Data.


The Impact of Range Oversampling Processing on Tornado Velocity Signatures Obtained from WSR-88D Super-Resolution Data. 

Authors: Torrres, S.M. and Curtis, C.D.

Journal: Journal of Atmospheric and Oceanic Technology

Publication Date: Online 7/28/15

 Important Conclusions:

Researchers applied “range oversampling,” a technique that cuts radar update times in half while increasing the accuracy of the data, to WSR-88D super-resolution data. WSR-88D super-resolution data allows for improved detection of weaker and more distant tornadoes by providing an enhancement of the tornadic vortex signature.  In this work, researchers used simulations to determine that the benefits of range-oversampling processing outweigh the relatively small degradation to the range resolution. It was shown that this process can contribute to the tornado warning decision process by improving forecaster confidence in the radar data.


The paper quantifies the impact of range oversampling on super-resolution data. This is important in the context of research-to-operations since range oversampling is scheduled for future operational implementation on the WSR-88D.

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Latest weather radar research on display this week

Weather radar research is a key part of NSSL’s mission in support of the NOAA National Weather Service (NWS). This week, NSSL/CIMMS scientists will share the latest in weather radar research at the American Meteorological Society’s 2013 Conference on Radar Meteorology in Breckenridge, Colo.

Phased array radar research presentations include:

  • An overview of the latest improvements to the National Weather Radar Testbed
  • Phased Array Radar (NWRT PAR) capabilities to demonstrate Multi-function
  • Phased Array Radar (MPAR) program weather and aviation requirements
  • How NWS forecasters’ responded to rapid, adaptive phased array radar sampling and if it increased their ability to effectively cope with tough tornado
  • warning cases
  • New techniques to increase the NWRT PAR scan rate and reduce observation
  • times
  • NWRT PAR observations of microburst events
  • A method to detect and characterize storm merges and splits using rapidly updating NWRT PAR observations in thunderstorm models

NSSL/CIMMS researchers also work with current weather radars in operation and will present:

  • A new algorithm that combines output from a forecast model with dual-polarized radar data to more accurately estimate what winter weather is occurring between the lowest scan of the radar and the ground.
  • A study of how NSSL’s products that estimate precipitation amounts improved using dual-polarized radar data
  • Evaluation of existing hail size estimation algorithms
  • Crowdsourced reports precipitation types at the ground using the “meteorological Phenomena Identification Near the Ground” (mPING) smart phone app
  • Development of a database of U.S. flash flood events using NSSL’s Severe Hazards Analysis and Verification Experiment, and mPING reports
  • Improvements in radar wind data quality control

Other presentations include mobile radar observations of a tornadic supercell and rainfall in the Mediterranean region and airborne radar observations of precipitation in the Indian Ocean.

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A tribute to the “Father of NEXRAD”

Dale Sirmans
Dale Sirmans

For many in the weather radar community, Dale Sirmans is recognized as the father of the NEXt-Generation RADar (NEXRAD). As the lead engineer and principal architect of NSSL’s first 10-cm Doppler weather radar, his leadership and guidance helped bring Doppler radar to the National Weather Service.  Sirmans recently passed away on December 23 in Albertville, Ala., at 76, and we wanted to celebrate his five decades of contributions to weather radar, weather science and to the careers of future engineers and scientists.

Sirmans started at NSSL during the early 1960’s, making key contributions to the understanding of Doppler weather radar theory.  He led his team to build one of the first 10-cm Doppler weather radar systems in the world for investigating the use of Doppler measurements for severe weather detection.  This radar became the prototype for the current NEXRAD, or Weather Surveillance Radar -1988 Doppler (WSR-88D) network.

Since Doppler weather radar was new to the weather community, Sirmans also made significant contributions by identifying the most efficient Doppler weather radar data estimation and analysis techniques.  He meticulously documented and reported his findings, and many of the techniques are still used today, or formed the foundation for new developments.

By the early 1980’s, most of the science and basic engineering principles necessary to develop a usable Doppler weather radar were understood.  This attracted attention from the National Weather Service, the U.S. Air Force’s Air Weather Service, and the Federal Aviation Administration.  They decided to form a Joint System Program Office (JSPO) to develop a new NEXRAD radar network for the nation.  Sirmans played a key role in the full-scale development of the WSR-88D system and by the end of the 1980’s the U.S. government had a first production version of the WSR-88D ready for validation.

As the research radar technology transitioned into national deployment and operations, Sirmans left NSSL to become the first Chief of the new NEXRAD Operational Support Facility (OSF) Engineering Branch, effectively becoming the Chief Engineer for all WSR-88D operations.  He retired briefly then returned to the OSF (later renamed the Radar Operations Center) as an employee of the OSF support contractor, supporting the Nation’s network of radars by documenting performance and solving unique technical problems.  Every area of the WSR-88D benefited from his expertise, from basic hardware to radome cleaning processes.

Sirmans also had the ability to impact the lives and careers of people he knew, mentoring a new generation of engineers and scientists who will carry on his work.  His dedication to his work continued until his death, and his contributions have helped forecasters save thousands of lives.

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Phased array radar captures evolution of a tornado at close range

Phased array radar scan verses WSR-88D scan of rotation in a storm

Subtle features in thunderstorms captured by rapid scanning phased array radar could alert forecasters to the potential of severe weather.

NSSL researchers used the National Weather Radar Testbed (NWRT) Phased Array Radar(PAR) to sample a tornadic supercell at a close 20km range for the first time.

The storm occurred on May 13, 2009 in central Oklahoma and produced an EF-0 tornado, heavy rain, and hailstones up to 2.5cm in diameter.

The storm also provided a unique research opportunity as it moved in-between the research radar and the National Weather Service WSR-88D operational radar. Because data were collected from two radars on the same storm, special analysis techniques were applied to estimate wind fields not usually obtainable by a single radar. This “dual-Doppler” analysis technique revealed subtle interactions inside the storm before the tornado formed.

Recent analysis of this storm revealed the 43 second update time of the PAR provided a much better depiction of the evolution of the tornado’s parent circulation than the 4.2 minute update time of the WSR-88D. The study also suggests that the tornado’s parent circulation resulted from the merging of two circulations, observed by several scans of PAR and the one scan of the WSR-88D.

Phased array radar technology uses an array of transmit and receive elements on a flat panel, and can collect the same weather information as a WSR-88D radar but in about one-sixth the time.  NSSL researchers continue to demonstrate PAR technology provides improved detection of severe weather hazards.

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