Publications
ITWS microburst prediction algorithm performance, capabilities, and limitations
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems,. Oklahoma City, 13-15 November, 1996.
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Summary
Lincoln Laboratory, under funding from the Federal Aviation Administration (FAA) Terminal Doppler Weather Radar program, has developed algorithms for automatically detecting microbursts. While microburst detection algorithms provide highly reliable warnings of microbursts. there still remains a period of time between microburst onset and pilot reaction during which aircraft are at risk. This latency is due to the time needed for the automated algorithms to operate on the radar data, for air traffic controllers to relay any warnings and for pilots to react to the warnings. Lincoln Laboratory research and development has yielded an algorithm for accurately predicting when microburst outflows will occur. The Microburst Prediction Algorithm is part of a suite of weather detection algorithms within the Integrated Terminal Weather System. This paper details the performance of the Microburst Prediction Algorithm over a wide range of geographical and climatological environments. The paper also discusses the full range of the Microburst Prediction Algorithm's capabilities and limitations in varied weather environments. This paper does not discuss the overall rationale for a prediction algorithm or the detailed methodology used to generate predictions.
Summary
Lincoln Laboratory, under funding from the Federal Aviation Administration (FAA) Terminal Doppler Weather Radar program, has developed algorithms for automatically detecting microbursts. While microburst detection algorithms provide highly reliable warnings of microbursts. there still remains a period of time between microburst onset and pilot reaction during which aircraft are at...
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A comparative performance study of TDWR/LLWAS 3 integration algorithms for wind shear detection
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, Oklahoma City, 13-15 November, 1996.
Summary
This paper gives a brief overview of the history of the development of the TDWR/LLWAS 3 integration algorithms, a brief overview of the various algorithms, and a discussion of the comparative evaluation of the TDWR, LLWAS 3, and the three candidate TDWR/LLWAS 3 integration algorithms. This is followed by a more detailed description of the TDWR/LLWAS 3 integration algorithm chosen by the FAA for production, and a brief overview of the ITWS/LLWAS 3 integration algorithm.
Summary
This paper gives a brief overview of the history of the development of the TDWR/LLWAS 3 integration algorithms, a brief overview of the various algorithms, and a discussion of the comparative evaluation of the TDWR, LLWAS 3, and the three candidate TDWR/LLWAS 3 integration algorithms. This is followed by a...
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ASR-9 Weather Systems Processor (WSP): wind shear algorithms performance assessment
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems,. Oklahoma City, 13-15 November, 1996.
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Summary
Under Federal Aviation Administration sponsorship, Lincoln Laboratory has developed a prototype Airport Surveillance Radar Weather Systems Processor (ASR-WSP). This prototype has been used for field measurements and operational demonstrations since 1987. Measurements so acquired provide an extensive database for development and validation of the algorithms used by the WSP to generate operational wind shear information for Air Traffic Controllers. In this paper we assess the performance of the current versions of the WSP's microburst and gust front wind shear detection algorithms on data from each of the locations at which our prototype system has operated. Evaluation of the associated environmental characteristics (e.g., storm structure, radar ground clutter environment) allows for generalization of these results to the major U.S. climatic regimes where the production version of WSP will be deployed.
Summary
Under Federal Aviation Administration sponsorship, Lincoln Laboratory has developed a prototype Airport Surveillance Radar Weather Systems Processor (ASR-WSP). This prototype has been used for field measurements and operational demonstrations since 1987. Measurements so acquired provide an extensive database for development and validation of the algorithms used by the WSP to...
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Analysis of the 12 April 1996 wind shear incident at DFW airport
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
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Summary
Wind shear detection algorithms that operate on Doppler radar data are tuned to primarily recognize the velocity and reflectivity signatures associated with microbursts and gust fronts. Microbursts produce a divergent pattern in the velocity field that is associated with a descending column of precipitation. Gust fronts produce a convergent pattern that is often associated with a thin-line reflectivity feature. On April 12, 1996 at Dallas-Fort Worth International Airport (DFW) three pilots reported encounters with wind shear in a five minute period (2329-33 GMT). The third pilot (AA 1352) reported an encounter with "severe wind shear", which we refer to as "the incident" throughout the paper. He used maximum throttle to keep the MD-80 in the air and reported that it was only "by the grace of God" that the aircraft did not crash (Dallas Morning News, 4/19/96). The plane, originally bound for Pittsburgh, was diverted to Tulsa where the passengers were offloaded to another aircraft, the black box was removed, and the engines were checked according to procedures required whenever maximum throttle is utilized.
Summary
Wind shear detection algorithms that operate on Doppler radar data are tuned to primarily recognize the velocity and reflectivity signatures associated with microbursts and gust fronts. Microbursts produce a divergent pattern in the velocity field that is associated with a descending column of precipitation. Gust fronts produce a convergent pattern...
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Comparison of the performance of the Integrated Terminal Weather System (ITWS) and Terminal Doppler Weather Radar (TDWR) microburst detection algorithms
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
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Summary
This paper describes the designs of the TDWR and ITWS Microburst Detection algorithms, and compares their performances in the Orlando, FL and Memphis, TN environments. This is the first study in which the performance of the TDWR and ITWS microburst detection algorithms are compared using an identical data set and a common set of truth criteria. Examples are presented illustrating common scenarios which create the performance differences. Detail is presented on the impact of the ITWS VIL (Vertically Integrated Liquid water) test in reducing algorithm false alarms. This algorithm feature is currently being considered as a retrofit to the TDWR algorithm.
Summary
This paper describes the designs of the TDWR and ITWS Microburst Detection algorithms, and compares their performances in the Orlando, FL and Memphis, TN environments. This is the first study in which the performance of the TDWR and ITWS microburst detection algorithms are compared using an identical data set and...
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Discussion of the impact of data contamination on TDWR algorithm performance
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
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Summary
The Federal Aviation Administration (FAA) is currently deploying Terminal Doppler Weather Radars (TDWRs) at key airports in the continental U.S. that experience high volumes of traffic and high frequencies of thunderstorm impact. The TDWR is designed to display the location and intensity of storm cells as well as the location and intensity of wind shear events in the airport vicinity. The TDWR system uses clutter filters and four data quality editing techniques: point target removal, clutter residue editing maps (CREMs), range obscuration editing, and velocity dealiasing in an attempt to reduce base data contamination prior to wind shear algorithm processing. The performance of the wind shear detection algorithms is directly related to the quality of the base data. In particular, failures of the data quality editors can seriously degrade the wind shear detection algorithm's performance. It will be shown that these failures can lead to both undetected and false events. In addition, clutter contamination from nonmeteorological sources such as birds can produce false wind shear signatures in the radar data. This paper will examine the impact of data contamination on algorithm performance at key TDWR sites where base and products data have been collected. The severity of these failures will be discussed, along with possible solutions to the most significant problems.
Summary
The Federal Aviation Administration (FAA) is currently deploying Terminal Doppler Weather Radars (TDWRs) at key airports in the continental U.S. that experience high volumes of traffic and high frequencies of thunderstorm impact. The TDWR is designed to display the location and intensity of storm cells as well as the location...
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Feedback from the users of commissioned TDWR systems
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems,. Oklahoma City, 13-15 November, 1996.
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Summary
The primary mission of the Terminal Doppler Weather Radar (TDWR) system is to detect thunderstorm-related wind shears and microbursts that are potentially hazardous to aircraft during landing and takeoff operations (e.g.. within three nautical miles on final approach and within two nautical miles on departure). The sources of these wind shears are microbursts and gust fronts. The mechanism by which these wind shears are provided to Air Traffic Controllers is the Ribbon Display Terminal. A secondary mission of the TDWR system is to support traffic management by the detection of precipitation and detection and forecast of gust-front-induced wind shift. This information is provided to the Air Traffic managers (Supervisors and Traffic Management Coordinators) via the Situation Display. The TDWR Program Office tasked Massachusetts Institute of Technology Lincoln Laboratory to survey the first five commissioned TDWR sites in order to assess how well the system was meeting its mission goals and to measure user (Air Traffic Controllers and air traffic managers such as Supervisors, Traffic Management Coordinators, etc.) benefits achieved through deployment of the TDWR. A list of candidate questions was prepared (Appendix A). Site visits commenced on 28 November 1995 and ended 25 January 1996. At each site, interviews began with a tour of the Air Traffic Control Tower. Questions regarding airport configuration, number of operations, and weather impact on operations were asked to provide a context for controller and traffic manager interviews. Users who acted in the capacity of controller were asked questions regarding their perceptions (If the accuracy of the Ribbon Display Terminal messages and their views of the impact (if any) on the effectiveness with which they performed their duties. Users who performed the duties of traffic managers (Controllers-in-Charge, Supervisors, Traffic Management Coordinators) were asked questions about the operational benefits of the products on the Situation Display. After the interview process was completed, the benefits estimates claimed for the TDWR system were revisited.
Summary
The primary mission of the Terminal Doppler Weather Radar (TDWR) system is to detect thunderstorm-related wind shears and microbursts that are potentially hazardous to aircraft during landing and takeoff operations (e.g.. within three nautical miles on final approach and within two nautical miles on departure). The sources of these wind...
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Machine intelligent gust front algorithm for the Terminal Doppler Weather Radar (TDWR) and Integrated Terminal Weather System (ITWS)
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
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Summary
Thunderstorms often generate gust fronts that can have significant impact on airport operations. Unanticipated changes in wind speed and direction are of concern from an air traffic safety viewpoint (hazardous wind shear) as well as from an airport planning point of view (runway configuration). Automated gust front detection is viewed by FAA and the air traffic community as an important component of current and future hazardous weather detection systems including the Terminal Doppler Weather Radar (TDWR), ASR-9 with Weather Systems Processor (ASR-9 WSP), and the Integrated Terminal Weather Systems (ITWS) for which TDWR is a principal sensor. In cooperation with the FAA, Lincoln Laboratory has successfully developed and tested a real-time Machine Intelligent Gust Front Algorithm (MIGFA) for use with Doppler weather radars. This algorithm resulted from the successful fusion of two complementing technologies developed at Lincoln Laboratory: computer vision/machine intelligence techniques originally developed for automated target recognition, and automated product-oriented weather radar data processing. Using these techniques, a version of MIGFA designed for use with TDWR has demonstrated substantial improvement over the existing TDWR gust front algorithm, detecting more and greater extents of gust fronts with fewer false alarms. MIGFA is slated to eventually replace the existing TDWR gust front algorithm and will be used as the gust front algorithm for the planned ITWS and ASR-9 WSP systems. A brief overview of techniques used by MIGFA to identify and track gust fronts will bre presented in this paper. More details, along with recent detection performance results, can be obtained from prior publications. However, detection and tracking of a gust front is only part of the task. Once the location of a gust front has been determined, the associated wind shear estimate and wind shift forecast must be computed. Several issues arises. For example, a gust front can be tens of kilometers in length, with outflow strength and contrasting environmental winds varying considerably along its length. Where along the front should the wind shear analysis be performed? Also, for airport planning purposes, air traffic controllers and managers need to plan runway configuration based on winds that may change suddenly when a gust front moves over the airport. Depending on the nature of the gust front, some of these winds are relatively transient while others are more persistent. How should the wind shift advisory produced by the algorithm take this into account? MIGFA uses a consensus derived from a variety of estimation techniques as a robust means of generating wind shear and wind shift estimates for detected gust fronts. These techniques, and some of their limitations, are discussed. Results of comparisons of MIGFA-generated wind shear and wind shift reports against observations are also presented. The paper concludes by outlining planned enhancements to incorporate additional information available under ITWS that should further improve the quality of MIGFA's wind shear and wind shift forecasts.
Summary
Thunderstorms often generate gust fronts that can have significant impact on airport operations. Unanticipated changes in wind speed and direction are of concern from an air traffic safety viewpoint (hazardous wind shear) as well as from an airport planning point of view (runway configuration). Automated gust front detection is viewed...
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The Terminal Weather Information for Pilots program
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems,. Oklahoma City, 13-15 November, 1996.
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Summary
The Federal Aviation Administration (FAA) is currently sponsoring programs such as the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS) which will significantly improve the aviation weather information in the terminal area. Given the great increase in the quantity and quality of this information, it would be highly desirable to provide this data directly to pilots rather than having to rely on voice communications. Providing terminal weather information automatically via data link would both enhance pilot awareness of potential weather hazards and reduce air traffic controller workload. The Terminal Weather Information for Pilots (TWLP) program was created to address these needs. This paper will describe the philosophy behind the product, the format of the TWIP messages. and the system design. An interesting weather case from the operational demonstration currently underway will be shown, and plans for the national deployment of the TWIP capability at all TDWR-based airports will be discussed.
Summary
The Federal Aviation Administration (FAA) is currently sponsoring programs such as the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS) which will significantly improve the aviation weather information in the terminal area. Given the great increase in the quantity and quality of this information, it would...
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A 16-element subarray for hybrid-circuit tile-approach spatial power combining
November 1, 1996
Journal Article
Published in:
IEEE Trans. Microw. Theory Tech., Vol. 44, No. 11, November 1996, pp. 2093-8.
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Summary
Three designs for a 4-by-4 are described for use in a spatial power-combined transmitter. The subarrays are constructed using a hybrid-circuit, tile-approach architecture and are composed of 16 cavity-backed, proximity-coupled microstrip antennas, each fed by a 0.5 watt amplifier. Both linearly and circularly polarized subarrays have been constructed for operation over a 10% band centered at 10 GHz. The linearly polarized subarray showed the following peak performance: EIRP greater than 27 dBW, effective transmitter power greater than 5 watts, dc-RF efficiency greater than 20%, and excellent graceful degradation performance.
Summary
Three designs for a 4-by-4 are described for use in a spatial power-combined transmitter. The subarrays are constructed using a hybrid-circuit, tile-approach architecture and are composed of 16 cavity-backed, proximity-coupled microstrip antennas, each fed by a 0.5 watt amplifier. Both linearly and circularly polarized subarrays have been constructed for operation...
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