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Data requirements for ceiling and visibility products development
April 13, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-212
Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of weather products important for air traffic control in the terminal area. These products will take advantage of new terminal area sensors, including Terminal Doppler Weather Radar (TDWR, Next Generation Weather Radar (NEXRAD), and the Meteorological Data Collection and Reporting System (MDCRS). Some of these ITWS products will allow air traffic managers to anticipate significant short-term changes in ceiling and visibility. This report focuses on the scientific data requirements for supporting prototype model-system development and diagnostics. Model diagnostics can include case studies to determine the most important physical processes that were responsible for a particular ceiling and visibility "event," providing the insight necessary for the development of effective ceiling and visibility product algorithms. In time such case study diagnostics could also include careful off-line "failure analyses" that may affect the disign of the operational system. General ceiling and visibility test beds are discussed. Updated reports will be released periodically as the ITWS ceiling and visibility project proceeds.
Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of weather products important for air traffic control in the terminal area. These products will take advantage of new terminal area sensors, including Terminal Doppler Weather Radar (TDWR, Next Generation Weather Radar (NEXRAD), and the Meteorological...
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Extrapolating storm location using the Integrated Terminal Weather System (ITWS) storm motion algorithm
March 29, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-208
Summary
Storm Motion (SM) is a planned Initial Operational Capability (IOC) algorithm of the FAA's Integrated Terminal Weather System (ITWS). As currently designed, this algorithm will track the movement of storms/cells and convey this tracking information to the ITWS user by means of a graphic display of vectors (for direction) with accompanying numeric reports of storm speed, rounded to the nearest 5 nmi/hr increment. Recognizing that there are occasions when ITWS users could benefit from a more extended product format, Storm Extrapolated Position (SEP) was conceived to supplement the SM product and thereby increase the latter's accessibility as a planning aid. This communication describes a prototype SEP design along with an analysis of its accuracy and observed performance during 1993 ITWS demnstrations in Orlando (FL) and Dallas (TX).
Summary
Storm Motion (SM) is a planned Initial Operational Capability (IOC) algorithm of the FAA's Integrated Terminal Weather System (ITWS). As currently designed, this algorithm will track the movement of storms/cells and convey this tracking information to the ITWS user by means of a graphic display of vectors (for direction) with...
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The polygon-ellipse method of data compression of weather maps
March 28, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-213
Summary
Providing an accurate picture of the weather conditions in the pilot's area of interest could be a highly useful application for ground-to-air data links. The problem with using data links to transmit weather pictures is the large number of bits required to exactly specify a weather image. To make transmission of weather maps practical, a means must be found to compress this image. The Polygon-Ellipse (PE) encoding algorithm developed in this report represents weather regions as ellipses, polygons, and exact patterns. The actual ellipse and polygon parameters are encoded and transmitted; the decoder algorithm redraws the shape from their encoded parameter values and fills in the included weather pixels. Special coding techniques are used in PE to compress the encoding of the shape parameters to achieve further overall compression. The PE algorithm contains procedures for gracefully degrading the fidelity of the transmitted image when necessary to meet a specified bit limit. Pictorial examples of the operation of this algorithm on both Terminal Doppler Weather Radar (TDWR) and ASR-9 radar-generated weather images are presented.
Summary
Providing an accurate picture of the weather conditions in the pilot's area of interest could be a highly useful application for ground-to-air data links. The problem with using data links to transmit weather pictures is the large number of bits required to exactly specify a weather image. To make transmission...
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Machine Intelligent Gust Front Algorithm
November 4, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-196
Summary
The Federal Aviation Administration has sponsored research and development of algorithms for automatic gust front detection as part of a suite of hazardous weather detection capabilities for airports. These algorithms are intended for use with Doppler radar systems, specifically the Terminal Doppler Weather Radar (TDWR) and the Airport Surveillance Radar enhanced with a Wind Shear Processor (ASR-9 WSP). Although gust fronts are observable with fairly reliable signatures in TDWR data, existing gust front detection algorithms have achieved only modest levels of detection performance. For smaller airports not slated to receive a dedicated TDWR, the ASR-9 WSP will provide a less expensive wind shear detection capability. Gust front detection in ASR-9 SP data is an even more difficult problem, given the reduced sensitivity and less reliable Doppler measurements of this radar. A Machine Intelligent Gust Front Algorithm (MIGFA) has been constructed at Lincoln Laboratory that is a radical departure from previous design strategies. Incorporating knowledge-based, signal-processing techniques initially developed at Lincoln Laboratory for automatic target recognition, MIGFA uses meterological knowledge, spatial and temporal context, conditional data fusion, delayed thresholding, and pixel-level fusion of evidence to improve gust front detection performance significantly. In tests comparing MIGFA with an existing state-of-the-art algorithm applied to ASR-9 WSP data, MIGFA has substantially outperformed the older algorithm. In fact, by some measures, MIGFA has done as well or better than human interpreters of the same data. Operational testing of this version was done during 1992 in Orlando, Florida. The desing, test results, and performance evaluation of hte ASR-9 WSP version of MIGFA are presented in this report, which was prepared as part of the documentation package for the ASR-9 WSP gust front algorithm.
Summary
The Federal Aviation Administration has sponsored research and development of algorithms for automatic gust front detection as part of a suite of hazardous weather detection capabilities for airports. These algorithms are intended for use with Doppler radar systems, specifically the Terminal Doppler Weather Radar (TDWR) and the Airport Surveillance Radar...
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Estimation of wake vortex advection and decay using meteorological sensors and aircraft data
September 28, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-201
Summary
The lift-generated wake vortices trailing behind an aircraft present a danger to aircraft following the same or nearby path. The degree of hazard to the following aircraft depends on the nature of the wake encountered in its flight path and on the ability of the aircraft to counter its effects. This report describes the current state of understanding of the factors that influence the motion and dissipation of wake vortices. The relationships of these factors to parameters that are measurable through meteorological sensors and from a priori knowledge of the vortex generating aircraft characteristics are discussed as an aid to structuring development plans for the creation of wake vortex advisory products by the Integrated Terminal Weather System (ITWS) and by special wake vortex sensors.
Summary
The lift-generated wake vortices trailing behind an aircraft present a danger to aircraft following the same or nearby path. The degree of hazard to the following aircraft depends on the nature of the wake encountered in its flight path and on the ability of the aircraft to counter its effects...
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Integrated Terminal Weather System (ITWS) 1992 Annual Report
September 7, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-203
Summary
Hazardous weather in the terminal area is the major cause of aviation system delays as well as a principal cause of air carrier accidents. Several systems presently under development will provide significant increases in terminal safety. However, these systems will not make a major impact on weather-induced delays in the terminal area, meet a number of the safety needs (such as information to support ground deicing decisions), or reduce the workload of the terminal controller. The Integrated Terminal Weather System (ITWS) will provide improved aviation weather information in the allocated TRACON area (up to 50 nmi from the airport) by integrating data and products from various Federal Aviation Administration (FAA) and National Weather Service (NWS) sensors and weather information systems. The data from these sources will be combined to provide a unified set of safety and planning weather products for pilots, controllers, and terminal area traffic managers. by using data from multiple sensors, ITWS can generate important new products where no individual sensor alone could generate a single, reliable product. In other instances, use of data from several sources can compensate for erroneous data from one sensor and thus improve the overall integrity of existing products. Major objectives of the ITWS program are to increase the effective airport acceptance rate in adverse weather by rpoviding information to support terminal automation systems, better terminal route planning, and wake vortex advisory services, and to reduce the need for controllers to communicate weather information to pilots via VHF voice. This report summarizes the work acocmplished during fiscal year 1992 on the development of the ITWS initial operational capability products; functional prototype design; operation of testbeds to acquire data for product development and testing; operation evaluation of products by ATC users; investigation of approaches for effective transfer of the technology to the production contractor; transfer of products to pilots via digital data links; and technical support for the ITWS documents required by the General Accounting Office (GAO).
Summary
Hazardous weather in the terminal area is the major cause of aviation system delays as well as a principal cause of air carrier accidents. Several systems presently under development will provide significant increases in terminal safety. However, these systems will not make a major impact on weather-induced delays in the...
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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:
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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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Contributions to the American Meteorological Society's 26th International Conference on Radar Meteorology
April 1, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-199
Summary
Eleven papers contributed by the Lincoln Laboratory Weather Sensing Group to the American Meteorological Society's 26th International Conference on Radar Meteorology, to be held May 24-28, 1993 in Norman, Oklahoma, are compiled in this volume. The work reported was sponsored by several FAA programs, including Terminal Doppler Weather Radar (TDWR), Air Surveillance Radar-9 (ASR-9), Integrated Terminal Weather System (ITWS), and Terminal Area Surveillance System (TASS). The papers are based on analyses completed over the past year at Lincoln Laboratory and in collaboration with staff at the National Severe Storms Laboratory, the University of Oklahoma, Raytheon Corporation, and the FAA Technical Center in Atlantic City, NJ. The staff members of the Weather Sensing Group have documented their studies in four major areas: Operational Systems (TDWR Operational Test and Evaluation results); Radar Operations (future airport weather surveillance requirements, a "machine intelligent" gust front detection algorithm, microburst asymmetry study results, a shear-based microburst detection algorithm, and a hazard index for TDWR-detected microbursts); Signal Processing (coherent processing across multi-PRI waveforms, clutter filter design for multiple-PRT signals, and identification of anomalous propagation associated with thunderstorm outflows); and Analysis Methods (multiple-single Doppler wind analysis using NEXRAD data, and an adjoint method wind retrieval scheme).
Summary
Eleven papers contributed by the Lincoln Laboratory Weather Sensing Group to the American Meteorological Society's 26th International Conference on Radar Meteorology, to be held May 24-28, 1993 in Norman, Oklahoma, are compiled in this volume. The work reported was sponsored by several FAA programs, including Terminal Doppler Weather Radar (TDWR)...
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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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