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A machine intelligent gust front algorithm for Doppler weather radars
May 24, 1993
Conference Paper
Published in:
26th Int. Conf. on Radar Meteorology, 24-28 May 1993, pp. 654-656.
Summary
Gust fronts generated by thunderstorms can seriously affect the safety and efficiency of airport operations. Lincoln Laboratory, under contract with the Federal Aviation Administration (FAA), has had a significant role in the development of two Doppler radar systems that are capable of detecting low altitude wind shears, including gust fronts, in the airport terminal control area. These systems are the latest generation Airport Surveillance Radar, enhanced with a Wind Shear Processor (ASR-98 WSP) and the Terminal Doppler Weather Radar (TDWR).
Summary
Gust fronts generated by thunderstorms can seriously affect the safety and efficiency of airport operations. Lincoln Laboratory, under contract with the Federal Aviation Administration (FAA), has had a significant role in the development of two Doppler radar systems that are capable of detecting low altitude wind shears, including gust fronts...
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Anomalous propagation associated with thunderstorm outflows
May 24, 1993
Conference Paper
Published in:
Proc. 26th Int. Conf. on Radar Meteorology, 24-28 May 1993, pp. 238-240.
Topic:
R&D area:
R&D group:
Summary
Battan noted that ducting of radar energy by anomalous atmospheric refractive index profiles and resulting abnormally strong ground clutter can occur during three types of meteorological circumstance: (i) large scale boundary layer temperature inversions and associated sharp decrease in moisture with height -- these are often created by nocturnal radiative cooling; (ii) warm, dry air moving over cooler bodies of water, resulting in cooling and moistening of air in the lowest levels; (iii) cool, moist outflows from thunderclouds. In contrast to the first two types of anaomalous propagation (AP), radar ducting associated with thunderstorm outflows is quite dynamic and may mimic echoes from precipitating clouds in terms of spatial scale and temporal evolution. While non-coherent weather radars (e.g. WSR-57) are obviously susceptible to false storm indications from this phenomemenon, Doppler radars that select the level of ground clutter suppression based on "clear day maps" may also fail to suppress the AP-induced ground clutter echoes. Operational Doppler radar systems known to be susceptible to this phenomena are the National Weather Service's WSR-88D and the Federal Aviation Administration's Airport Surveillance Radar (ASR-9) six-level weather channel. In this paper, characteristics of thunderstorm outflow-generated AP are documented using data from a testbed ASR-9 operated at Orlando, Florida. The testbed radar's rapid temporal update (4.8 seconds per PPI scan) and accurate scan-to-scan registration of radar resolution cells enabled characterization of the spatial and temporal evolution of the AP-induced clutter echoes. We discuss implications of these phenomenological characteristics on operational systems, specifically the ASR-9. Algorithms for discrimination between true precipitation echoes and AP-induced ground clutter are discussed.
Summary
Battan noted that ducting of radar energy by anomalous atmospheric refractive index profiles and resulting abnormally strong ground clutter can occur during three types of meteorological circumstance: (i) large scale boundary layer temperature inversions and associated sharp decrease in moisture with height -- these are often created by nocturnal radiative...
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Clutter filter design for multiple-PRT signals
May 24, 1993
Conference Paper
Published in:
Proc. 26th Int. Conf. on Radar Meteorology, 24-28 May 1993, pp. 235-237.
Summary
The trade-off of range vs. velocity ambiguity is fundamental and operationally significant for many S- and C-band pulsed Doppler weather radars. Transmission schemes using multiple pulse repetition times (PRTs) (i.e., nonuniform pulse spacing) offer the potential for extending the unambiguous measurement range by resolving intervals of velocity ambiguity. Unfortunately, multiple PRT methods can be problematic with low-elevation scanning when ground clutter removal is required. We have constructed both Chebyshev and mean-squared error (MSE) desing algorithms (Choroboy, 1993) that deal with design in the complex domain; the MSE algorithms are described below.
Summary
The trade-off of range vs. velocity ambiguity is fundamental and operationally significant for many S- and C-band pulsed Doppler weather radars. Transmission schemes using multiple pulse repetition times (PRTs) (i.e., nonuniform pulse spacing) offer the potential for extending the unambiguous measurement range by resolving intervals of velocity ambiguity. Unfortunately, multiple...
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The Memphis Precision Runway Monitor Program Instrument Landing System final approach study
May 24, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-194
Summary
This report documents the study of the lateral positions of aircraft on Instrument Landing System (ILS) approaches during the Memphis, Tennessee, Precision Runway Monitor (PRM) demonstration. The PRM is an advanced radar monitoring system that improved the arrival capacity of closely spaced parallel runways in poor weather conditions. The results of this study are used to assist in determining the minimum runway spacing that will he authorized for PRM. The objective of this study was to quantify the lateral character of ILS arrivals and the consequent impact on independent simultaneous ILS arrival to closely spaced parallel runways. The sensitivity of the arriving aircrafts' lateral positions to different variables such as visibility, wind runway, aircraft type, autopilot performance, and localizer beam width was determined. Also, the Memphis arrival data were compared to FAA Technical Center Chicago O'Hare approach data. The analysis was primarily based on surveillance reports of 4,000 ILS arrivals into Memphis International Airport, collected with the PRM AMPS sensor (ATCRBS Monopulse Processing System). A major result of the study was that lateral aircraft positions will not hamper independent arrivals to parallel runways spaced 3,400 feet apart, but will impede operations at 3,000 feet or smaller unless approach modifications are introduced. Lateral deviations were found to be most sensitive to reduced visibility and certain autopilots. Lateral deviations were also found to be somewhat more at Memphis relative to Chicago O'Hare. Recommendations for further data analysis and collection are discussed.
Summary
This report documents the study of the lateral positions of aircraft on Instrument Landing System (ILS) approaches during the Memphis, Tennessee, Precision Runway Monitor (PRM) demonstration. The PRM is an advanced radar monitoring system that improved the arrival capacity of closely spaced parallel runways in poor weather conditions. The results...
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Machine intelligent gust front detection
March 1, 1993
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 6, No. 1, Spring 1993, pp. 187-212.
Summary
Techniques of low-level machine intelligence, originally developed at Lincoln Laboratory to recognize military ground vehicles obscured by camouflage and foliage, are being used to detect gust fronts in Doppler weather radar imagery. This Machine Intelligent Gust Front Algorithm (MIGFA) is part of a suite of hazardous-weather-detection functions being developed under contract with the Federal Aviation Administration. Initially developed for use with the latest generation Airport Surveillance Radar equipped with a wind shear processor (ASR-9 WSP), MIGFA was deployed for operational testing in Orlando, Florida, during the summer of 1992. MIGFA has demonstrated levels of detection performance that have not only markedly exceeded the capabilities of existing gust front algorithms, but are competitive with human interpreters.
Summary
Techniques of low-level machine intelligence, originally developed at Lincoln Laboratory to recognize military ground vehicles obscured by camouflage and foliage, are being used to detect gust fronts in Doppler weather radar imagery. This Machine Intelligent Gust Front Algorithm (MIGFA) is part of a suite of hazardous-weather-detection functions being developed under...
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Setting values for TDWR/LLWAS 3 integration parameters
February 5, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-195
Summary
In 1993 the FAA will begin deploying the Terminal Doppler Weather Radar (TDWR) at selected airports in the United States. Forty-five TDWRs will be collocated with LLWAS 3 systems, and the FAA has decided that all TDWRs collocated with LLWAS 3 systems must be integrated with LLWAS 3 prior to commissioning. The algorithm chosen to perform this integration must be supplied with a set of site-specific parameters. This report gives guidance on how to set the values of theme integration parameters.
Summary
In 1993 the FAA will begin deploying the Terminal Doppler Weather Radar (TDWR) at selected airports in the United States. Forty-five TDWRs will be collocated with LLWAS 3 systems, and the FAA has decided that all TDWRs collocated with LLWAS 3 systems must be integrated with LLWAS 3 prior to...
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Results of simulation studies of precision runway monitoring of independent approaches to closely-spaced parallel runways
January 1, 1993
Journal Article
Published in:
J. ATC, January-March 1993, pp. 18-24.
Summary
Increased air travel in recent years has resulted in a steady increase in the number and duration of flight delays. In an attempt to increase airport capacity, MIT Lincoln Laboratory, under the sponsorship of the Federal Aviation Administration (FAA), has supported the development of a Precision Runway Monitor (PRM). The PRM is an advanced radar monitoring system designed to increase utilization of closely-spaced, multiple, parallel runways during adverse weather conditions. The PRM consists of radar which has higher accuracy and a faster update interval than the current system, and a high resolution, color display that informs the Monitor Controller of the occurrence of hazardous flight path deviations by means of automated visual and vocal warning alerts. Studies of air traffic controller reaction to the PRM were conducted at Memphis Airport and Raleigh-Durham Airport in order to evaluate system effectiveness and to assess the effects of key variables on controller reaction time. This paper documents the results of the controller studies conducted at Memphis by MIT Lincoln Laboratory. The testing consisted of the presentation of real-time simulations, and measurement of air traffic controllers were surveyed regarding the acceptability of the PRM.
Summary
Increased air travel in recent years has resulted in a steady increase in the number and duration of flight delays. In an attempt to increase airport capacity, MIT Lincoln Laboratory, under the sponsorship of the Federal Aviation Administration (FAA), has supported the development of a Precision Runway Monitor (PRM). The...
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The Terminal Doppler Weather Radar (TDWR) Moving Target Simulator (MTS) at Orlando, Florida
August 20, 1992
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-188
Summary
Monitoring the performance of Doppler weather radars presents special problems since target returns cannot be verified by reference to other systems (e,g ., as ASR-9 aircraft reports can be compared with beacon replies). The Terminal Doppler Weather Radar (TDWR) system includes a Moving Target Simulator (MTS) which provides a point target equivalent to a 50 dBZ reflectivity weather return with an apparent radial velocity of 5 m/s. This report describes the installation results for a prototype MTS using the TDWR testbed radar in Orlando, FL. Procedures were developed for improved aiming of the MTS, using aiming of the MTS, using azimuth and elevation adjustments, which are recommended to be incorporated in the production MTS installation procedure. Initial data analyses indicate that the MTS returns from a typical radio tower would be useful for integrity monitoring in fair weather using typical TDWR filters. The use of the MTS when high -reflectivity weather or anomalous propagation (AP) is present needs further study.
Summary
Monitoring the performance of Doppler weather radars presents special problems since target returns cannot be verified by reference to other systems (e,g ., as ASR-9 aircraft reports can be compared with beacon replies). The Terminal Doppler Weather Radar (TDWR) system includes a Moving Target Simulator (MTS) which provides a point...
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Birds mimicking microbursts on 2 June 1990 in Orlando, Florida
July 10, 1992
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-184
Summary
During 1990 and 1991, the Terminal Doppler Weather Radar (TDWR) testbed collected Doppler radar measurements in Orlando, Florida in support of the TDWR Project. The main focus of the project is to develope algorithms that automatically detect wind shears such as microbursts anti gust fronts. While the primary goal of the TDWR is to detect scattering from raindrops, the sensitivity of the system allows for the detection of biological echoes as well. Previous research has shown that under certain conditions the scattering from birds and insects will lead to divergent signatures that mimic microbursts. This type, of pattern has been documented in Alabama (Rinehart, 1986), Illinois (Larkin and Quine, 1989), and Missouri (Evans, 1990). In the Alabama and Illinois events, a divergent pattern similar to a microburst was produced when a large number of birds departed in the early morning hours from an overnight roosting site. On 2 June 1990 in Orlando, Florida, there were 11 surface divergent signatures similar to microbursts detected by the TDWR testbed radar. The maximum differential velocity of these events ranged from 11 to 36 m/s, while the maximum reflectivity varied from 0 to 44 dBz. There was light rain in the area and low-reflectivity returns aloft; however, the reflectivity was more like low-reflectivity microbursts in Denver than high-reflectivity microbursts that generally are observed in Orlando. These divergences were not detected by the microburst algorithm since the TDWR site adaptation parameters have been adjusted to avoid issuing alarms for signatures such as those on 2 June. Detailed investigation was conducted of two events to verify that these were not actual microbursts. Single Doppler radar features identified in earlier observations of divergence signatures caused by birds in Alabama and Missouri, as well as features suggested by NEXRAD researchers, were considered. The results of the radar data analysis could not unequivocally determine that birds caused the divergent signatures. A microburst prediction model developed by Wolfson was applied to the data using sounding results from Cape Canaveral, Florida to determine whether the apparent velocities were consistent with current theories of microburst generation. This model analysis clearly indicated a nonweather-related cause for the divergent signatures observed on 2 June. We conclude from the microburst prediction analysis and certain oddities in the divergence radar signatures that birds probably accounted for these divergences.
Summary
During 1990 and 1991, the Terminal Doppler Weather Radar (TDWR) testbed collected Doppler radar measurements in Orlando, Florida in support of the TDWR Project. The main focus of the project is to develope algorithms that automatically detect wind shears such as microbursts anti gust fronts. While the primary goal of...
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Airport Surveillance Radar (ASR-9) Wind Shear Processor - 1991 Test at Orlando, Florida
June 1, 1992
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-189
Summary
An operational test of a Wind Shear Processor (WSP) add-on to the Federal Aviation Administration's airport surveillance radar (ASR-9) took place at Orlando International Airport during July and August 1991. The test allowed for both quantitative assessment of the WSP's signal processing and wind shear detection algorithms and for feedback from air traffic controllers and their supervisors on the strengths and weaknesses of the system. Thunderstorm activity during the test period was intense; low-altitude wind shear impacted the runways or approach/departure corridors on 40 of the 53 test days. As in previous evaluations of the WSP in the southeastern United States, microburst detection performance was very reliable. Over 95% of the strong microbursts that affected the Orlando airport during the test period were detected by the system. Gust front detection during the test, while operationally useful, was not as reliable as it should have been, given the quality of gust front signatures in the base reflectivity and radial velocity data from the WSP. Subsequent development of a Machine Intelligent gust front algorithm has resulted in significantly improved detection capability. Results from the operational test are being utilized in ongoing refinement of the WSP.
Summary
An operational test of a Wind Shear Processor (WSP) add-on to the Federal Aviation Administration's airport surveillance radar (ASR-9) took place at Orlando International Airport during July and August 1991. The test allowed for both quantitative assessment of the WSP's signal processing and wind shear detection algorithms and for feedback...
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