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Implementation of the 1992 Terminal Area-Local Analysis and Prediction System (T-LAPS)
August 22, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-219
Summary
The Integrated Terminal Weather System (ITWS) development program was initiated by the Federal Aviation Administration (FAA) to produce a fully automated, integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service (NWS) sensors as well as from aircraft in flight in the terminal area. The ITWS will provide air traffic personnel with products that are immediately usable without further metorological interpretation. These products include current terminal area weather and short-term (0-30 minute) predictions of significant weather phenomena. The Terminal area-Local Analysis and Prediction System (T-LAPS) is being evaluated as a possible provider of the Terminal Winds Product for the ITWS. T-LAPS is a direct descendant of the Local Analysis and Prediction System (LAPS) developed at the National Oceanic and Atmospheric Administraiton's (NOAA's) Forecast Systems Laboratory (FSL). T-LAPS takes meteorological data from a wide variety of data sources as input and provides a gridded, three-dimensional (3-D) analysis of the state of the local atmosphere in the terminal area as output. For the 1992 system, the output was a gridded 3-D analysis of the horizontal winds. This information is intended to be used by the Terminal Air Traffic Control Automation (TATCA) program to estimate the effects of winds on aircraft in the terminal area. The 1993 and 1994 T-LAPS systems will incorporate more sophisticated wind analysis algorithms. The T-LAPS '92 demonstration at the Lincoln Laboratory Terminal Doppler Weather Radar (TDWR) FL-2CC field site in Kissimmee, Florida, during August and September was quite successful. The primary area of coverage was a 120 km by 120 km box centered on the Orlando International Airport. The T-LAPS system was able to utilize radar information from both the TDWR testbed and the operational NEXRAD/WSR-88D radar in Melbourne, Florida. This report documents the implementation of the T-LAPS system that was run during the 1992 summer demonstration and discusses the design and some implementation details of the system.
Summary
The Integrated Terminal Weather System (ITWS) development program was initiated by the Federal Aviation Administration (FAA) to produce a fully automated, integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service (NWS)...
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Terminal Doppler Weather Radar (TDWR) Low Level Wind Shear Alert System 3 (LLWAS 3) integration studies at Orlando International Airport Airport in 1991 and 1992
April 20, 1994
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-216
Summary
In 1993 the Federal Aviation Administration (FAA) began deploying two new wind shear detectionsystems: the Terminal Doppler Weather Radar (TDWR) and the third-generation Low Level Windshear Alert System (LLWAS 3). Currently, nine airports are scheduled to receive both a TDWR and an LLWAS 3. This number may eventually increase to as high as 45. When co-located, the systems will be integrated to provide a single set of wind shear alerts and improve system performance. The TDWR production schedule required one of three integration algorithms to be chosen for specification by fall 1991. The three algorithms are the prototype integration algorithm developed at the National Center for Atmospheric Research (NCAR) and two algorithms developed at MIT Lincoln Laboratory (MIT/LL). To assess the performance of the three algorithms, MIT/LL performed a study of the integration, TDWR, and LLWAS 3 algorithms at Orlando International Airport in the summer of 1992. We discuss results of the 1991 comparative study and a follow-up study of the TDWR, LLWAS 3, and Message Level integration algorithms at Orlando in 1992. All of the algorithms met the requirement of detecting 90 percent of microburst level wind shear with loss events. LLWAS 3, Build 5 TDWR, and the MIT/LL integration algorithms run with Build 5 TDWR, all met the requirement that less than 10 percent of wind shear alerts be false. The NCAR prototype did not utilize Build 5 TDWR. Build 4 TDWR and all integration algorithms run with Build 4 TDWR did not meet the false-alert requirement. Detailed descriptions of the algorithms are given. The methodology for estimating various algoirthm performance statistics based on a comparison with a dual-Doppler algorithm is detailed.
Summary
In 1993 the Federal Aviation Administration (FAA) began deploying two new wind shear detectionsystems: the Terminal Doppler Weather Radar (TDWR) and the third-generation Low Level Windshear Alert System (LLWAS 3). Currently, nine airports are scheduled to receive both a TDWR and an LLWAS 3. This number may eventually increase to...
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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
Topic:
R&D area:
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:
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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