Publications
Use of features aloft in the TDWR microburst recognition algorithm
March 27, 1989
Conference Paper
Published in:
Proc. 24th Conf. on Radar Meteorology, 27-31 March 1989, pp. 167-170.
Topic:
R&D area:
R&D group:
Summary
This paper describes the use of features aloft in the Terminal Doppler Weather Radar (TWDR) microburst recognition algorithm. The paper is divided into three sections: algorithm description, scan strategy and recent results. The prototype algorithm recognizes features aloft associated with microbursts, such as descending reflectivity cores and convergence aloft. The algorithm uses these signatures to improve the detection performance and timeliness of microburst hazard warnings. For example, the algorithm can use features aloft to make a microburst declaration while the surface outflow is still weak, thereby increasing the hazard warning time. An important factor in microburst recognition algorithm performance is the scan strategy employed. The TDWR scan strategy is designed for timely detection of microburst surface outflows and features aloft. The rationale for the prototype TDWR scan strategy is presented using Denver's Stapleton airport as an example. Recent results are presented demonstrating the ability of the system to recognize features aloft for microburst events observed during the summer of 1988 at Denver, CO. It is shown that the ability to recognize features aloft improved the probability of detection and hazard warning time for these events.
Summary
This paper describes the use of features aloft in the Terminal Doppler Weather Radar (TWDR) microburst recognition algorithm. The paper is divided into three sections: algorithm description, scan strategy and recent results. The prototype algorithm recognizes features aloft associated with microbursts, such as descending reflectivity cores and convergence aloft. The...
READ MORE
An analysis of microburst characteristics related to automatic detection from Huntsville, Alabama and Denver, Colorado
March 1, 1989
Conference Paper
Published in:
24th Conf. on Radar Meteorology, 27-31 March 1989, pp. 269-273.
Topic:
R&D area:
R&D group:
Summary
During 1986 and 1987-8, Lincoln Laboratory, under the sponsorship of the Federal Aviation Administration (FAA), collected Doppler radar measurements in Huntsville, Alabama and Denver, Colorado, respectively. These field programs focused on developing and evaluating an automated wind shear detection system that would provide timely warnings of hazardous low-altitude wind shear events to pilots in the airport terminal area. Two previous projects in Denver (JAWS and CLAWS) documented the ability of a pulsed Doppler radar system to detect wind shear near an airport. In the last two decades, there have been 27 aircraft accidents or incidents at least partially attributed to this phenomenon. According to the National Transportation Safety Board, the most hazardous form of wind shear to aviation is the microburst, first identified by Fujita (1981). A microburst is an outflow of downdraft winds from a convective cloud which exhibits a strong divergent pattern near the surface. The radial velocity differential (delta V) must be greater than or equal to 10 m/s over a distance of 4 km or less to be classified as a microburst. In this paper, microburst measurements from the TDWR testbed are analyzed to characterize and compare the type of outflows in an environment with a typically dry sub-cloud layer (Denver) and a typically moist sub-cloud layer (Huntsville), and to relate these characteristics wo observable radar features being used in the Terminal Doppler Weather Radar (TDWR) system for microburst detection. Section 2 describes the primary radar used in the data collection program. Section 3 contrasts microburst characteristics from the two locales. Evidence is presented which suggests that the reflectivity and intensity of the outflow are important to the performance of the microburst detection algorithm, while the frequency and intensity of features aloft may provide for an earlier declaration of a microburst. In section 4, key microburst characteristics from Huntsville and Denver are summarized in relation to the automatic detection process.
Summary
During 1986 and 1987-8, Lincoln Laboratory, under the sponsorship of the Federal Aviation Administration (FAA), collected Doppler radar measurements in Huntsville, Alabama and Denver, Colorado, respectively. These field programs focused on developing and evaluating an automated wind shear detection system that would provide timely warnings of hazardous low-altitude wind shear...
READ MORE
Selected wind shear events observed during the 1987 evaluation of enhancements to the FAA low level wind shear alert system at Stapleton International Airport
February 15, 1989
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-158
Summary
The Federal Aviation Administration (FAA) Technical Center (FAATC) conducted a test of the enhancements to the FAA Low Level WInd Shear Alert System (LLWAS) at Denver Stapleton International Airport from 3 August through 4 September 1987. Upon completion of the test, the performance of the LLWAS during selected microburst and gust front test cases was investigated in detail. Additional sources of "true" wind shear information were sought to help evaluate the performance of the LLWAS. In support of these efforts, Lincoln Laboratory supplied complete data sets, including single Doppler radar data from the FAA-Lincoln Laboratory FL-2 radar, dual Doppler radar data from the FAA-Lincoln Laboratory FL-2 radar, dual Doppler analyses of the surface wind fields (when possible), mesonet data from the Lincoln network of 30 automatic weather stations in the vicinity of Stapleton, and LLWAS data to the FAATC. This report provides a summary of salient features for a number of FAATC selected wind shear events which occured during the evaluation of the enhanced LLWAS, and documents the data that Lincoln Laboratory has provided to the FAA as part of its project responsibilities.
Summary
The Federal Aviation Administration (FAA) Technical Center (FAATC) conducted a test of the enhancements to the FAA Low Level WInd Shear Alert System (LLWAS) at Denver Stapleton International Airport from 3 August through 4 September 1987. Upon completion of the test, the performance of the LLWAS during selected microburst and...
READ MORE
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.
Topic:
R&D area:
R&D group:
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...
READ MORE
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.
Topic:
R&D area:
R&D group:
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...
READ MORE
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.
Topic:
R&D area:
R&D group:
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...
READ MORE
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.
Topic:
R&D area:
R&D group:
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...
READ MORE
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.
Topic:
R&D area:
R&D group:
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...
READ MORE
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.
Topic:
R&D area:
R&D group:
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, 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...
READ MORE
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.
Topic:
R&D area:
R&D group:
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 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...
READ MORE