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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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Observed differences between Denver and Kansas City gust fronts and their impact upon the performance of the gust front detection algorithm

Published in:
16th Conf. on Severe Local Storms/Conf. on Atmospheric Electricity, 22-26 October 1990, pp. 236-239.

Summary

The Terminal Doppler Weather Radar (TDWR) testbed radar (known as FL-2) collected data near Denver's Stapleton Airport during 1988 and near the Kansas City International Airport (MCI) during 1989. One objective of the TDWR Program is to detect gust fronts and their associated wind shifts. This information can be used by an Air Traffic Control (ATC) supervisor to plan runway changes and for warnings of potentially-hazardous gust front-related wind shears to arriving and departing pilots. This function is performed by the gust front detection algorithm. An ongoing assessment of the performance of the current TDWR gust front algorithm is necessary to ensure that the algorithm performs consistently in different environments. Such assessments were performed after the 1988 TDWR Operational Test and Evaluation in Denver and after the 1989 operational season in Kansas City. This paper presents a comparison of gust front characteristics such as length, duration, strength, and propagation speed and direction that occurred in Denver and Kansas City and a comparison of algorithm performance at each location. In the following, the term gust front refers to the leading edge of the thunderstorm outflow throughout its life cycle. A gust front event is a single observation of a gust front (on a radar volume scan) by the National Severe Storms Laboratory (NSSL) ground-truth analyst.
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Summary

The Terminal Doppler Weather Radar (TDWR) testbed radar (known as FL-2) collected data near Denver's Stapleton Airport during 1988 and near the Kansas City International Airport (MCI) during 1989. One objective of the TDWR Program is to detect gust fronts and their associated wind shifts. This information can be used...

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Gust front detection algorithm for the Terminal Doppler Weather Radar: part 2, performance assessment

Published in:
Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 398-402.

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).
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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...

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Gust front detection algorithm for the Terminal Doppler Weather Radar : part 1, current status

Published in:
Proc. Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 31-34.

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).
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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...

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Wind shear detection with pencil-beam radars

Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 483-510.

Summary

Abrupt changes in the winds near the ground pose serious hazards to aircraft during approach or departure operations. Doppler weather radars can measure regions of winds and precipitation around airports, and automatically provide air traffic controllers and pilots with important warnings of hazardous weather events. Lincoln Laboratory, as one of several organizations under contract to the Federal Aviation Administration, has been instrumental in the design and development of radar systems and automated weather-hazard recognition techniques for this application. The Terminal Doppler Weather Radar (TDWR) system uses automatic computer algorithms to ident* hazardous weather signatures. TDWR detects and warns aviation users about low-altitude wind shear hazards caused by microbursts and gust fronts. It also provides advance warning of the arrival of wind shifts at the airport complex. Extensive weather radar observations, obtained from a Lincoln-built transportable testbed radar system operated at several sites, have validated the TDWR system. As a result, the Federal Aviation Administration has issued a procurement contract for the installation of 47 TDWR radar systems around the country.
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Summary

Abrupt changes in the winds near the ground pose serious hazards to aircraft during approach or departure operations. Doppler weather radars can measure regions of winds and precipitation around airports, and automatically provide air traffic controllers and pilots with important warnings of hazardous weather events. Lincoln Laboratory, as one of...

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Preliminary results of the 1983 Coordinated Aircraft - Doppler weather radar turbulence experiment, volume 1

Published in:
MIT Lincoln Laboratory Report ATC-137-I

Summary

This report presents results of analyses of coordinated radar-aircraft data acquired form the 1983 experiment conducted at Hanscom AFB, Massachusetts. The objective of the experiment is to assess and validate the current NEXRAD algorithms for estimating aircraft turbulence from volume-scanned Doppler weather observations. Estimates of the turbulence severity index epsilon to the 1/3 power (a quantity used by NEXRAD) computed from radar and aircraft data are presented as a time series along each aircraft track. The radar point estimates of turbulence were averaged horizontally and vertically to yield layered Cartesian maps such as are intended for use by real time ATC controllers and pilots. The derived gust velocity (Ude), also used to indicate the intensity of aircraft encountered turbulence, was computed so that comparisons could be made of the turbulence intensity scales inferred from values of epsilon and U sub de. These quantitative comparisons indicate that for the turbulence generally encountered during the flights, both radar and aircraft estimates of epsilon to the 1/3 power significantly overstate the severity of turbulence as reported by the aircraft pilot. The data analysis also shows that radar-based estimates of epsilon to the 1/3 power, often significantly exceeded aircraft based estimates of epsilon to the 1/3 power. In contrast, the quantity Ude underestimates the aircraft reported turbulence intensity on all the flights. The uncertainty as to operationally useful thresholds for radar epsilon to the 1/3 power, aircraft epsilon to the 1/3 power and Ude is discussed as is the use of spectrum width as a turbulence indicator. It should be noted that the turbulence detection flights used in the study were conducted at ranges such that the radar resolution cell cross range extent was typically 1.5 to 3 km. With such resolution cell size extents, the hypothesis of spatially homogeneous turbulence may not hold and/or the assumed relationship of radar measured spectrum width to kinetic dissipation rate may not be fully accurate.
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Summary

This report presents results of analyses of coordinated radar-aircraft data acquired form the 1983 experiment conducted at Hanscom AFB, Massachusetts. The objective of the experiment is to assess and validate the current NEXRAD algorithms for estimating aircraft turbulence from volume-scanned Doppler weather observations. Estimates of the turbulence severity index epsilon...

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Gust front characteristics as detected by Doppler radar

Published in:
Mon. Weather Rev., Vol. 115, No. 5, May 1987, pp. 905-918.

Summary

Gust fronts produce low altitude wind shear that can be hazardous to aircraft operations, especially during takeoff and landing. Radar meteorologists have long been able to identify gust front signatures in Doppler radar data, but in order to use the radar efficiently, automatic detection of such hazards is essential. In a study designed to accumulate statistics on the gust frontal signature in Doppler radar data, nine gust front cases were analyzed. Data were collected on those characteristics thought to be most important in developing rules for automatic gust-front detection such as gust front length and height, maximum and minimum values of reflectivity, velocity and spectrum width, and estimates of radical shear. To provide the reader with a concrete example, photographs of the Doppler radar displays of just two (in the interest of brevity) of the nine gust fronts are presented and discussed, as well as summary data for all cases. For these cases, outflows could be detected most reliably in the velocity field. Line features in the spectrum width and reflectivity fields associated with some of the gust fronts could also be identified, although somewhat less reliably than in a Doppler velocity.
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Summary

Gust fronts produce low altitude wind shear that can be hazardous to aircraft operations, especially during takeoff and landing. Radar meteorologists have long been able to identify gust front signatures in Doppler radar data, but in order to use the radar efficiently, automatic detection of such hazards is essential. In...

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A gust front case studies handbook

Published in:
MIT Lincoln Laboratory Report ATC-129

Summary

Gust fronts produce low altitude wind shear that can be hazardous to aircraft operations, especially during takeoff and landing. Radar meteorologists have long been able to identify gust front signatures in Doppler radar data, but in order to use the radars efficiently, automatic detection of such hazards is essential. Eight gust front case studies are presented. The data include photographs of the Doppler weather radar displays, thermodynamic and wind measurements from a 440 m high tower, environmental soundings and tables of gust front characteristics. The tabulated characteristics are those thought to be most important in developing rules for automatic gust front detection such as length and height, maximum and minimum values of reflectivity, velocity and spectrum width, and estimates of radial shear. For the cases studied, outflows could be detected most reliably in the velocity field, but useful information also could be gleaned from the spectrum width and reflectivity fields. The signal-to-noise ratio threshold was found to be a major factor in the ability of an observer to discern the gust front signature in the Doppler radar displays. Detection within the spectrum width field required a higher SNR than did the radial velocity field.
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Summary

Gust fronts produce low altitude wind shear that can be hazardous to aircraft operations, especially during takeoff and landing. Radar meteorologists have long been able to identify gust front signatures in Doppler radar data, but in order to use the radars efficiently, automatic detection of such hazards is essential. Eight...

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An automatic weather station network for low-altitude wind shear investigations

Published in:
MIT Lincoln Laboratory Report ATC-128

Summary

During the summer of 1983 an experimental network of automatic weather stations (a mesonet) was operated in the vicinity of Hanscom Field, northwest of Boston, as part of a larger effort to collect Doppler radar and meteorological data on thunderstorms and other potentially hazardous weather events in this area. This report describes the mesonet system used and presents in detail the data collected on 21-22 July 1983. Conclusions about the limitations and the future use of the mesonet system are also included.
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Summary

During the summer of 1983 an experimental network of automatic weather stations (a mesonet) was operated in the vicinity of Hanscom Field, northwest of Boston, as part of a larger effort to collect Doppler radar and meteorological data on thunderstorms and other potentially hazardous weather events in this area. This...

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