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Distribution of aviation weather hazard information: low altitude wind shear

Published in:
Ninth Conf. on Aviation, Range, and Aerospace Meteorology, 11-15 September 2000, pp. 499-504.

Summary

Weather Hazard Information distribution is a necessary component for a successful system of weather hazard avoidance for aviation. It is a very important component, but not the only one. In order to be successful, a complete set of components must be included in the system: 1) Accurate Conceptual Model (Appropriate models of the physical process responsible for generating the hazard); 2) Production Infrastructure (System of tools [hardware, software and manpower]; the raw data feeds necessary for production of the hazard information and a standardized message format); 3) Quality Control Infrastructure (System of tools [hardware, software and manpower] & data feeds necessary for identifying and correcting erroneous information immediately); 4) Distribution Infrastructure (A method to relay, in a timely manner, only the information pertinent to the specific user); 5) Policies and Procedures (There must be clearly defined expectations of actions required of the users and recipients of the hazard information); 5) Training (The users and recipients as well as individuals responsible for production and quality control of the information must receive initial and recurrent training regarding actions required). ICAO in their Annex 3, Chapter 7 titled, SIGMET Information, Aerodrome Warnings and Wind Shear Warnings [ICAO 19981, describes in part one such system for weather hazard avoidance. ICAO does a good job defining the necessary production infrastructure. ICAO especially has been successful in defining the standardized message format. The format for SlGMETs is described in detail in Annex 3. But, an international organization Such as ICAO is limited in its scope of influence. Quality control of the SIGMET product and the distribution of the SIGMET is, in large part, beyond ICAO’s control. In addition, the actual weather hazard avoidance policies, procedures and training must be accomplished internally by each individual commercial aviation operator. Since each component listed above is directly dependent on the other five for a successful weather hazard avoidance system, Northwest Airlines (NWA) has chosen to attempt to address all six components of the system internally with use of the NWA Turbulence Plot System (TPS) [Fahey et. al. 2000].
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Summary

Weather Hazard Information distribution is a necessary component for a successful system of weather hazard avoidance for aviation. It is a very important component, but not the only one. In order to be successful, a complete set of components must be included in the system: 1) Accurate Conceptual Model (Appropriate...

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Preliminary results of the weather testing component of the Terminal Doppler Weather Radar operational test and evaluation

Published in:
Proc. 26th Int. Conf. on Radar Meteorology, 24-28 May 1993, pp. 29-34.

Summary

The Terminal Doppler Weather Radar (TDWR) system which has been developed by Raytheon Co. for the Federal Aviation Administration (FAA), provides automatic detection of microbursts and low-altitude wind shear. Microburst- and gust front-induced wind shear can result in a sudden, large change in airspeed which can have disastrous effect on aircraft performance. during take off or landing. The second major function of TDWR is to improve air traffic management through forecasts of wind shifts, precipitation and other weather hazards. The TDWR system generates Doppler velocity, reflectivity, and spectrum width data. The base data are automatically dealiased and clutter is removed through filtering and mapping. Precipitation and windshear products, such as microbursts and gust fronts, are displayed as graphic products on the Geographic Situation Display which is intended for use by Air Traffic Control supervisors. Alphanumeric messages indicating the various windshear alerts and derived airspeed losses and gains are sent to a flat panel ribbon display which is used by the controllers in the control tower. The TDWR proof-of-concept and operational feasibility have been demonstrated in a number of FAA-sponsored tests and evaluations conducted by Massachusetts Institute of Technology's Lincoln Laboratory (MIT/LL) in Memphis, TN (1985); Huntsville, AL (1986); Denver, CO (1987, 1988); Kansas City, MO (1989, and Orlando, FL (1990-1992). In order to verify that the TDWR meets FAA operational suitability and effectiveness requirements, an Operational Test & Evaluations (OT&E) was conducted at the Oklahoma City site during the period from 24 August to 30 October 1992. The testing addressed National Airspace System (NAS)-SS-1000 requirements, weather detection performance, safety, operational system performance, maintenance, instruction books, Remote Maintenance Monitoring System (RMMS), system adaptable parameters, bullgear wear, and limited Air Traffic (AT) suitability. The TDWR OT&E Integration and Operational testing was conducted using a variety of methods dependent on the area being tested. This paper discusses primarily the weather detection performance testing. A rough analysis was performed on the algorithm output and the base data to determine the performance of the TDWR in detecting wind shear phenomena. Final results will be available after additional testing, which is scheduled for Spring of 1993, and post analysis in conducted.
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Summary

The Terminal Doppler Weather Radar (TDWR) system which has been developed by Raytheon Co. for the Federal Aviation Administration (FAA), provides automatic detection of microbursts and low-altitude wind shear. Microburst- and gust front-induced wind shear can result in a sudden, large change in airspeed which can have disastrous effect on...

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High resolution microburst outflow vertical profile data from Huntsville, Alabama, and Denver, Colorado

Author:
Published in:
MIT Lincoln Laboratory Report ATC-163

Summary

The purpose of this report is to present detailed data on microburst outflows recorded by the TDWR testbed radar (FL-2) in Huntsville, Alabama (1986) and Denver, Colorado (1987-88). Whenever possible, a microburst detected within 10 km of the radar was scanned in a vertical direction (RHI) at 1 to 2 degree azimuthal intervals about the center of divergence. The vertical profile of the outflow is pertinent to the detection capability and siting strategy of a single Doppler radar observing the microburst from a horizontal viewing angle. Additionally, outflow features are important in assessing the hazard associated with microbursts as well as the capability of other wind shear detection (LLWAS or ASR). Of particular interest is the variability of outflows depths from case to case and site to site. If the depth across the maximum velocity differential is shallow, an outflow might go undetected or underestimated by a radar, the beam ot which was not viewing the axis of peak divergence. Previous research projects in Denver reported the highest winds in a microburst typically occur near the surface with an average outflow depth (1/2 peak velocity) ranging between 500 and 600 meters: however, the vertical resolution of these data was fairly crude due to the scan strategies utilized. This report provides detailed high resolution microburst outflow vertical profile data pertinent to TDWR system studies based on RHI and closely spaced PPI scans. The median observed outflow depth in Huntsville was 200 meters shallower than in Denver while the median height of the maximum velocity varied from 100 meters AGL in Huntsville to 200 meters AGL in Denver. For those Denver events presented here, we recommend that the TDWR microburst detection scan extend to at least 200 meters AGL and 100 meters if there is adequate clutter suppression.
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Summary

The purpose of this report is to present detailed data on microburst outflows recorded by the TDWR testbed radar (FL-2) in Huntsville, Alabama (1986) and Denver, Colorado (1987-88). Whenever possible, a microburst detected within 10 km of the radar was scanned in a vertical direction (RHI) at 1 to 2...

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Characteristics of thunderstorm-generated low altitude wind shear: a survey based on nationwide Terminal Doppler Weather Radar testbed measurements

Summary

The characteristics of microbursts and gust fronts, two forms of aviation-hazardous low altitude wind shear, are presented. Data were collected with a prototype terminal Doppler weather radar and a network of surface weather stations in Memphis, Huntsville, Denver, Kansas City, and Orlando. Regional differences and features that could be exploited in detection systems such as the associated reflectivity, surface wind shear, and temperature change are emphasized.
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Summary

The characteristics of microbursts and gust fronts, two forms of aviation-hazardous low altitude wind shear, are presented. Data were collected with a prototype terminal Doppler weather radar and a network of surface weather stations in Memphis, Huntsville, Denver, Kansas City, and Orlando. Regional differences and features that could be exploited...

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A case study of the Claycomo, Missouri microburst on July 30, 1989

Published in:
16th Conf. on Severe Local Storms/Conf. on Atmospheric Electricity, 22-26 October 1990, pp. 388-392.

Summary

The Terminal Doppler Weather Radar (TDWR) testbed collected thunderstorm measurements in the Kansas City area from March 27 through October 6, 1989. Of the 393 microbursts detected by the radar, 21 were classified as severe, with a differential velocity > 24 m/s. None of the severe events impacted terminal operations at Kansas City International Airport (KCI). Nevertheless, there were 42 microbursts within 3 nautical miles of the airport.
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Summary

The Terminal Doppler Weather Radar (TDWR) testbed collected thunderstorm measurements in the Kansas City area from March 27 through October 6, 1989. Of the 393 microbursts detected by the radar, 21 were classified as severe, with a differential velocity > 24 m/s. None of the severe events impacted terminal operations...

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A case study of the 24 August 1986, FLOWS microburst

Published in:
MIT Lincoln Laboratory Report ATC-162

Summary

From 1984 to 1986, Lincoln Laboratory under the sponsorship of the Federal Aviation Administration (FAA) collected wind shear measurements in the southeastern United States using a pulsed Doppler radar. The major emphasis of the measurement program and subsequent analyses is the development and testing of algorithms that will enable the Terminal Doppler Weather Radar (TDWR) to provide wind shear warnings to the aviation community by detection and tracking gust fronts and microbursts. An important phase of the program involves determining appropriate scan strategies and algorithms to detect other radar measurable features which precede or accompany the surface outflows of microbursts. The detection of features aloft such as convergence, rotation, divergence, storm cells, and descending reflectivity cores may permit advanced recognition of the wind shear while it is less than 10 m/s. In this report a microburst on 24 August 1986 in Huntsville is analyzed with single and dual-Doppler techniques to assess microburst precursors, asymmetry, and forcing mechanisms which could be used for futute algorithm development. The microburst producing storm formed within a moist adiabatic, unstable air-mass with weak wind shear at low to mid-levels of the atmosphere. Rotation, convergence, divergent tops, and a descending core were detected prior to the outflow attaining a divergence of 10 m/s. This storm is similar to other Huntsville microburst producing cells in exhibiting upper-level divergence prior to the initial microburst outflow. Previous analyses of wind shear in Denver and Oklahoma did not discuss divergent tops as a possible microburst precursor. However, its relation to storm severity and hailstorm intensity has been reported by Witt and Nelson (1984) and NEXRAD Program Office (1985). In this case-study, the 3-dimensional microburst detection algorithm provided an early declaration of the event while the radial velocity differential was less than 10 m/s.
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Summary

From 1984 to 1986, Lincoln Laboratory under the sponsorship of the Federal Aviation Administration (FAA) collected wind shear measurements in the southeastern United States using a pulsed Doppler radar. The major emphasis of the measurement program and subsequent analyses is the development and testing of algorithms that will enable the...

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An analysis of microburst characteristics related to automatic detection from Huntsville, Alabama and Denver, Colorado

Author:
Published in:
24th Conf. on Radar Meteorology, 27-31 March 1989, pp. 269-273.

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.
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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...

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