Publications
Using features aloft to improve timeliness of TDWR hazard warnings
February 7, 1989
Conference Paper
Published in:
Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 184-189.
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Summary
The Terminal Doppler Weather Radar (TDWR) has an operational requirement to provide a one minute advance warning for aircraft encountering a hazardous wind shear. This paper describes the use of features aloft in the prototype TDWR microburst recognition algorithm to improve the timeliness of microburst hazard warnings. The use of features aloft allows the algorithm to make a microburst declaration while the surface outflow is still weak, thereby increasing the hazard warning time. In addition, current work indicates that these signatures can also be used to predict the onset of surface outflow for high-reflectivity events. An initial version of the microburst recognition algorithm using surface velocity data only was described by Merritt (1987). Initial work on the use of features aloft to increase the reliability and timeliness of microburst alarms was described in Campbell, 1988. This work was motivated by the desire to emulate the ability of human experts to use features aloft to enhance the timeliness of microburst warnings (McCarthy & Wilson, 1986). This research was further influences by the conceptual models for the evolution of low, medium and high reflectivity microburst events in the Denver area proposed by Roberts and Wilson (1986), and by studies of features aloft associated with microbursts in the Southeast (Isaminger, 1987). The current TDWR microburst recognition algorithm is described in Campbell and Merritt, 1988. The present paper presents results demonstrating the ability of the prototype algorithm to recognize features aloft for microburst events observed at Huntsville, AL and Denver, CO. It is shown that the ability to recognize features aloft improved the hazard warning time for these events. Initial results for microburst prediction are also presented.
Summary
The Terminal Doppler Weather Radar (TDWR) has an operational requirement to provide a one minute advance warning for aircraft encountering a hazardous wind shear. This paper describes the use of features aloft in the prototype TDWR microburst recognition algorithm to improve the timeliness of microburst hazard warnings. The use of...
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Gust front detection algorithm for the Terminal Doppler Weather Radar: part 2, performance assessment
February 3, 1989
Conference Paper
Published in:
Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 398-402.
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Summary
During the summer of 1988, the Terminal Doppler Weather Radar (TDWR) Operational Test and Evaluation (OT&E) was conducted near Denver, CO. One of the objectives of this test was to assess the performance of the Gust Front Detection and Wind Shift Algorithms (Gust Front Algorithm) to be used in the TDWR system. This paper presents an overview of the Gust Front Algorithm system from data collection to products displays and discusses the performance of the algorithm during the 1988 OT&E. Data editing, product generation, ground truth and scoring issues are addressed. Scoring results for the various products are presented and problems identified during the OT&E are discussed. The design of the Gust Front Algorithm is discussed in the companion paper (Part 1 Current Status) numbered 1.6 in this preprint volume. The Gust Front Algorithm serves two functions: warning and planning. Warnings are provided in alphanumeric messages on a "Ribbon Display Terminal", Wind shear warnings are issued when a gust front impacts the runways or within 3 miles of the ends of the runways. The planning function consists of alerting an Air Traffic Control Supervisor when a change in wind speed and/or direction due to a gust front at the airport will occur within 20 minutes. This planning information is displayed on a Geographic Situation Usplay (GSD).
Summary
During the summer of 1988, the Terminal Doppler Weather Radar (TDWR) Operational Test and Evaluation (OT&E) was conducted near Denver, CO. One of the objectives of this test was to assess the performance of the Gust Front Detection and Wind Shift Algorithms (Gust Front Algorithm) to be used in the...
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Gust front detection algorithm for the Terminal Doppler Weather Radar : part 1, current status
February 3, 1989
Conference Paper
Published in:
Proc. Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 31-34.
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Summary
The gust front detection and wind shift algorithm is one of the two main algorithms developed for the Terminal Doppler Weather Radar (TDWR) program. This two-part paper documents some recent enhancements to, and the current status of, the algorithm (Part 1) and presents some results from recent testing of the algorithm during the TDWR Operational Test and Evaluation (OT&E) (Part 2: Klingle-Wilson et al., 1989).
Summary
The gust front detection and wind shift algorithm is one of the two main algorithms developed for the Terminal Doppler Weather Radar (TDWR) program. This two-part paper documents some recent enhancements to, and the current status of, the algorithm (Part 1) and presents some results from recent testing of the...
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Microburst recognition performance of TDWR operational testbed
February 3, 1989
Conference Paper
Published in:
Proc. Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 25-30.
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Summary
This paper describes current work in assessing the microburst recognition performance of the Terminal Doppler Weather Radar (TDWR) operational testbed. The paper is divided into three main sections: microburst recognition algorithm, performance assessment methodology and results. The first section provides an overview of the prototype TDWR microburst recognition algorithm The algorithm uses radar data from both surface scans and scans aloft to identify microburst events. The surface scan is used to identify microburst outflows, and the scans aloft provide information concerning reflectivity and velocity structures associated with microbursts to improve recognition rate and timeliness. The second section of the paper describes the methodology for assessing the recognition performance of the system. The performance of the testbed system is addressed from two viewpoints: radar detectability and pattern recognition capability. The issue of radar detectability is examined by comparing radar and mesonet data to determine if any events observed by the mesonet fail to be observed by the radar. The issue of pattern recognition performance is assessed by comparing microburst recognition algorithm outputs with truth as determined by expert radar meteorologists. The final section of the paper provides performance results for data collected by the testbed radar at Huntsville, AL and Denver, CO.
Summary
This paper describes current work in assessing the microburst recognition performance of the Terminal Doppler Weather Radar (TDWR) operational testbed. The paper is divided into three main sections: microburst recognition algorithm, performance assessment methodology and results. The first section provides an overview of the prototype TDWR microburst recognition algorithm The...
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The FAA Terminal Doppler Weather (TDWR) Program
February 3, 1989
Conference Paper
Published in:
Proc. Third Int. Conf. on the Aviation Weather Systems, 30 January - 3 February 1989, pp. 414-419.
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Summary
The Federal Aviation Administration (FAA) initiated the Terminal Doppler Weather Radar (TDWR) program in the mid-1980s in response to overwhelming scientific evidence that low-altitude wind shear had caused a number of major air-carrier accidents. The program is designed to develop a reliable automated system for detecting low-altitude wind shear in the terminal area and providing warnings that will help pilots successfully avoid it on approach and departure. Wind shear has caused more U.S. air-carrier fatalities than any other weather hazard. A 1983 National Research Council (NRC) study (National Research Council, 1983) identified low-altitude wind shear as the cause of 27 aircraft accidents and incidents between 1964 and 1982. A total of 488 people died in seven of these accidents, 112 of them in the 1975 crash of Eastern Flight 66 at New York and 153 in the crash of Pan American Flight 759 at New Orleans in 1982. Since the NRC study was completed, the National Transportation Safety Board (NTSB) has investigated at least three more wind-shear incidents. One of these, the crash of Delta Flight 191 at Dallas/Fort Worth on August 2, 1985, took another 137 lives. Wind shear is not a serious hazard for aircraft enroute between airports at normal cruising altitudes, but low-level wind shear in the terminal area can be deadly for an aircraft on approach or departure. The most hazardous form of wind shear is the microburst, an outflow of air from a small-scale but powerful downward gush of cold, heavy air that can occur beneath a thunderstorm or rain shower or even in rain-free air under a harmless-looking cumulus cloud. As this downdraft reaches the earth's surface, it spreads out horizontally, like a stream of water sprayed straight down on a concrete driveway from a garden hose. An aircraft that flies through a microburst at low altitude first encounters a strong headwind, then a downdraft, and finally a tailwind that produces a sharp reduction in airspeed and a sudden loss of lift. This deadly sequence of events caused the fatal crash at Dallas/Fort Worth in 1985, as well as a number of other serious air-carrier accidents. Wind shear can also be associated with gust fronts, warm and cold fronts, and strong winds near the ground. It is important for pilots to be trained in recovery techniques to use if they are caught in wind shear. But a sudden windspeed change of at least 40 to 50 knots, which is not uncommon in microbursts, presents a serious hazard to jet airliners, and some microbursts simply are non-survivable. The only sure way to survive wind shear in the terminal area is to avoid it. However, flight crews do not have adequate information available today to predict or detect wind shear. The primary goal of the IDWR program is to provide pilots with an objective, quantitative assessment of the wind-shear hazard. The TDWR system also will improve operational efficiency and reduce delays in the terminal area by providing air traffic control supervisors with timely warnings of impending wind shifts resulting from gust fronts.
Summary
The Federal Aviation Administration (FAA) initiated the Terminal Doppler Weather Radar (TDWR) program in the mid-1980s in response to overwhelming scientific evidence that low-altitude wind shear had caused a number of major air-carrier accidents. The program is designed to develop a reliable automated system for detecting low-altitude wind shear in...
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Weather sensing with airport surveillance radars
February 3, 1989
Conference Paper
Published in:
Proc. Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 68-74.
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Modern airport surveillance radars (ASR) are coherent, pulsed-Doppler radars used for detection and tracking of aircraft in terminal area air space. The Federal Aviation Agency (FAA is procuring over 100 next-generation ASR-9 radars for major US. airports while relocating existing ASR-8s to secondary terminals. Thus within the next five years, almost every U.S. airport that supports commercial operations will be equipped with one of these sensitive, highly stable S-band radars. In view of their on- or near-airport location, rapid scan rate and direct data link to air traffic control personnel, it has been recognized that ASRs can also provide flight controllers with timely information on weather conditions that are hazardous to aircraft. An ASR's transmitted frequency, power, pulse-to-pulse stability and receiver sensitivity are well suited for weather sensing. Conversely, its broad elevation beamwidth, rapid antenna scan rate and non-uniform pulse transmission sequence introduce significant complications for the quantitative interpretation of echoes returned from weather. This paper reviews principal results of a four-year, FAA-sponsored program to evaluate the capabilities and limitations of ASRs for measuring storm severity.
Summary
Modern airport surveillance radars (ASR) are coherent, pulsed-Doppler radars used for detection and tracking of aircraft in terminal area air space. The Federal Aviation Agency (FAA is procuring over 100 next-generation ASR-9 radars for major US. airports while relocating existing ASR-8s to secondary terminals. Thus within the next five years...
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Multisensor surveillance for improved aircraft tracking
January 1, 1989
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 381-396.
Summary
Cross-range measurements of aircraft travelling at distances of 50 to 200 miles include significant errors. Therefore, heading estimates for medium-to-long-range aircraft are not sufficiently accurate to be useful in conflict-detection predictions. Accurate crossrange measurements can be made-by using two or more sensors to measure aircraft position-but such measurements must compensate for the effects of system biases and aircraft turns. A set of algorithms has been developed that are resistant to system biases, that detect turns, and that track successfully through both biases and turns. These algorithms can be incorporated into a complete multisensor system, with good intersensor correlation of aircraft tracks and no added delays to the air traffic control processing chain.
Summary
Cross-range measurements of aircraft travelling at distances of 50 to 200 miles include significant errors. Therefore, heading estimates for medium-to-long-range aircraft are not sufficiently accurate to be useful in conflict-detection predictions. Accurate crossrange measurements can be made-by using two or more sensors to measure aircraft position-but such measurements must compensate...
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Parallel runway monitor
January 1, 1989
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 411-436.
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The availability of simultaneous independent approaches to parallel runways significantly enhances airport capacity. Current FAA procedures permit independent approaches in instrument meteorological conditions (IMC) when the parallel runways are spaced at least 4,300 ft apart. Arriving aircraft must be dependently sequenced at airports that have parallel runways separated by less than 4,300 ft, a procedure that reduces the arrival rate by as much as 250h. The need for greater airport capacity has led to intense interest in new technologies that can support independent parallel IMC approaches to runways spaced as close as 3,000 ft. This interest resulted in several FAA initiatives, including a Lincoln Laboratory program to evaluate the applicability of Mode-S secondary surveillance radars for monitoring parallel runway approaches. This paper describes the development and field activities of this program.
Summary
The availability of simultaneous independent approaches to parallel runways significantly enhances airport capacity. Current FAA procedures permit independent approaches in instrument meteorological conditions (IMC) when the parallel runways are spaced at least 4,300 ft apart. Arriving aircraft must be dependently sequenced at airports that have parallel runways separated by less...
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Propagation of mode S beacon signals on the airport surface
January 1, 1989
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 397-410.
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Many airports across the United States will soon be equipped with Mode S, a next generation beacon (or secondary) radar system. One feature of Mode S is that it provides a data link between airborne aircraft and air traffic controllers. If Mode S could be used to communicate with aircraft on the airport surface, the radar system would improve airport safety and efficiency on runways and taxiways. The airport surface, however, is a hostile propagation environment. This article outlines a candidate design for the propagation of Mode-S beacon signals on the airport surface. Data that support the feasibility of Mode S for surveilling runways and taxiways are presented.
Summary
Many airports across the United States will soon be equipped with Mode S, a next generation beacon (or secondary) radar system. One feature of Mode S is that it provides a data link between airborne aircraft and air traffic controllers. If Mode S could be used to communicate with aircraft...
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Wind shear detection with airport surveillance radars
January 1, 1989
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 511-526.
Summary
Airport surveillance radars (ASR) utilize a broad, cosecant-squared elevation beam pattern, rapid azimuthal antenna scanning, and coherent pulsed-Doppler processing to detect and track approaching and departing aircraft. These radars, because of location, rapid scan rate, and direct air traffic control (ATC) data link, can also provide flight controllers with timely information on weather conditions that are hazardous to aircraft. With an added processing channel, an upgraded ASR can automatically detect regions of low-altitude wind shear. This upgrade can provide wind shear warnings at airports where low traffic volume or infrequent thunderstorm activity precludes the deployment of a dedicated Terminal Doppler Weather Radar (TDWR). Field measurements and analysis conducted by Lincoln Laboratory indicate that the principal technical challenges for low-altitude wind shear detection with an ASR-groundclutter suppression, estimation of near-surface radial velocity, and automatic wind shear hazard recognition--can be successfully met for microbursts accompanied by rain at the surface.
Summary
Airport surveillance radars (ASR) utilize a broad, cosecant-squared elevation beam pattern, rapid azimuthal antenna scanning, and coherent pulsed-Doppler processing to detect and track approaching and departing aircraft. These radars, because of location, rapid scan rate, and direct air traffic control (ATC) data link, can also provide flight controllers with timely...
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