Publications
ITWS and ITWS/LLWAS-NE runway alert performance at Dallas-Ft. Worth and Orlando
September 11, 2000
Conference Paper
Published in:
Ninth Conf. on Aviation, Range, and Aerospace Meteorology, 11-15 September 2000, pp. 590-595.
Summary
The Integrated Terminal Weather System (ITWS) provides runway-orientated wind shear and microburst alerts to enhance the safety of flight operations at major U.S. airports. The alerts are reported as either losses or gains of airspeed, representing performance decreasing or performance increasing wind shears. The performance of ITWS as a stand-alone system has been thoroughly documented in previous research. During the 1994 ITWS Demonstration and Validation testing, the probability of detection (POD) and probability of false alarm (PFA) at Memphis (MEM) and Orlando (MCO) for all loss events were > 90 and < 5 percent, respectively, based on single-Doppler truth. The Low-Level Windshear Alert System-Network Expansion (LLWAS-NE) also generates runway alerts in the same format as ITWS. LLWAS-NE is not subject to viewing angle problems such as those experienced by single-Doppler radar. However, false alarms caused by LLWAS-NE sensor failures at some Terminal Doppler Weather Radar (TDWR) sites have reduced user confidence in the system. At those ITWS sites with an LLWAS-NE, the ITWS alerts derived from TDWR data will be integrated with LLWAS-NE alerts, hopefully to improve the performance. The ITWS integration algorithm is identical to the TDWR version, with the exception of a few adaptable parameter changes. The ITWS/LLWAS-NE parameters were modified slightly to account for ITWS and TDWR algorithm performance differences. In this paper, the performance of a stand-alone ITWS and the ITWS/LLWAS-NE integration algorithm at the MCO and Dallas-Ft. Worth (DFW) demonstration sites will be discussed. This assessment is considered unique since the radar and anemometer data were combined to create the runway truth. The focus of this research is to identify the shortcomings of both systems in order to recommend modifications that will improve the integration algorithm performance.
Summary
The Integrated Terminal Weather System (ITWS) provides runway-orientated wind shear and microburst alerts to enhance the safety of flight operations at major U.S. airports. The alerts are reported as either losses or gains of airspeed, representing performance decreasing or performance increasing wind shears. The performance of ITWS as a stand-alone...
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Measurement of hazardous winter storm phenomena at the Portland OR International Airport
September 11, 2000
Conference Paper
Published in:
Ninth Conf. on Aviation, Range, and Aerospace Meteorology, ARAM, 11-15 September 2000, pp. 525-530.
Summary
Wind shear and lightning are classically associated with summertime convective weather events at airports east of Reno, NV. However, a recent study concluded that severe wind shear and lightning strike events occasionally occur during winter storms at west coast airports. One of the most surprising findings was that the Portland Oregon International Airport (PDX) has operationally significant vertical wind shear and a surprisingly high number of lightning strikes to aircraft within the terminal area during winter storms. The FAA has for a number of years planned to install an ASR-9 Weather System Processor (WSP) at PDX to provide protection against wind shear from microbursts and gust fronts. However, in view of the findings of the west coast weather study (conducted after the FAA's wind shear deployment study was completed, a research program was undertaken to: Better understand the phenomenology associated with the Portland winter storms; Determine whether the baseline ASR-9 Weather System Processor planned for PDX would adequately address operationally significant wind shear and other safety-related weather phenomena; and Identify alternative sensing/data fusion approaches to providing PDX terminal weather decision support if the WSP alone could not adequately provide safety warnings.
Summary
Wind shear and lightning are classically associated with summertime convective weather events at airports east of Reno, NV. However, a recent study concluded that severe wind shear and lightning strike events occasionally occur during winter storms at west coast airports. One of the most surprising findings was that the Portland...
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An evaluation of the ASR-9 weather channel based on observations from the ITWS prototypes
September 23, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-270
Summary
The Federal Aviation Administration's (FAA) Airport Surveillance Radar (ASR-9) is a high-scan-rate system which provides a "critical" function in terms of air traffic control (ATC). In addition to its primary role of air traffic surveillance, the system also generates precipitation data for display on air traffic specialists' radar scopes and for use by automated systems such as the Integrated Terminal Weather System (ITWS) and Weather Systems Processor (WSP). Air traffic managers use these data to provide optimum routes for aircraft operating in and near the Terminal Radar Approach Control (TRACON) airspace. The primary advantage of the ASR-9 - as an aviation weather radar - over either the Terminal Doppler Weather Radar (TDWR) or the Next Generation Weather Radar (NEXRAD) is the rapid update rate, i.e., 30 seconds, which provides air traffic managers with a more accurate representation of weather echo location within the sensor's domain. This is far superior toeither the TDWR or NEXRAD, which takes from 2.5 to 6 minutes to create a volume scan, depending on the scan strategy. The sensor is also quite reliable, with limited down time. An analysis of ASR-9 data from the ITWS prototypes has uncovered a number of problems, which impact the quality of the precipitation data. The data quality issues discussed are overly aggressive ground clutter suppression, polarization mode issues, hardware failures associated with high beandlow beam switching, attenuatiodsignal depolarization, beam-filling losses, bright- band contamination, distant weather contamination, calibration issues, and radadantenna failures. The recommendations to address the ASR-9 data quality issues can be grouped into three categories: "Variable Site Parameter (VSP)" adjustments, hardware component maintenance checks, and automated flagging of data quality problems. The report includes discussion of the frequency and characteristics of each degradation, presenting both hardware and non- hardware related problems, and concludes with proposed solutions to the problems and recommendations designed to improve the overall utility of the ASR-9 precipitation data.
Summary
The Federal Aviation Administration's (FAA) Airport Surveillance Radar (ASR-9) is a high-scan-rate system which provides a "critical" function in terms of air traffic control (ATC). In addition to its primary role of air traffic surveillance, the system also generates precipitation data for display on air traffic specialists' radar scopes and...
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The benefits of using NEXRAD vertically integrated liquid water as an aviation weather product
January 10, 1999
Conference Paper
Published in:
8th Conf. on Aviation, Range, and Aerospace Meteorology (ARAM), 10-15 January 1999.
Summary
Over the past five years in which the Integrated Terminal Weather System (ITWS) testbed prototypes have been operational, there have been regular discrepancies noticed between the ASR–9 six–level precipitation product and the NEXRAD six–level maximum composite reflectivity product. (1. The NEXRAD composite product used in this study is the NEXRAD maximum composite reflectivity product which both the FAA and the ITWS use for weather data.). At the three prototypes in Memphis, Orlando and Dallas, staff have recognized that in certain situations the NEXRAD composite reflectivity product, which is the ITWS 100 and 200 nm long–range product, can be as much as three Video Integrator and Processor (VIP) levels higher than the ASR–9 precipitation product. This situation has caused some confusion for users of the ITWS system and concern on the part of system safety monitors. The confusion occurs because the two products do not agree with each other. Rhoda and Pawlak (1998) show that more aircraft will deviate around cells of ASR–9 VIP level 4 or greater than will penetrate them. There is also an aviation rule–of–thumb that pilots and air traffic specialists use which states cells of VIP level 3 or greater should be avoided if possible. This rule is a good guide but cannot be applied to the NEXRAD composite product. While the NEXRAD composite may show a cell with an intensity of level 3 or 4, the cell may contain very little of the higher–intensity precipitation while the bulk of the cell contains only level 2. This problem is magnified in the winter months when bright–band effects contaminate the radar data. Clutter [especially anomalous propagation (AP)] contamination of the composite reflectivity product is also a concern (especially when the AP is adjacent to actual weather returns). Differences between the two products will become more apparent with the fielding of the new ITWS situation display which has the capability of displaying both NEXRAD composite reflectivity and ASR–9 data side by side. In this study, we compare the NEXRAD composite reflectivity product with data from both the ASR–9 weather channel and an ASR–9 mosaic product as well as a Vertically Integrated Liquid water (VIL) product generated from NEXRAD base data.
Summary
Over the past five years in which the Integrated Terminal Weather System (ITWS) testbed prototypes have been operational, there have been regular discrepancies noticed between the ASR–9 six–level precipitation product and the NEXRAD six–level maximum composite reflectivity product. (1. The NEXRAD composite product used in this study is the NEXRAD...
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Performance characteristics of an algorithm used to remove anomolous propagation from the NEXRAD data
September 12, 1997
Conference Paper
Published in:
28th Conf. on Radar Meteorology, 7-12 September 1997, pp. 317-319.
Summary
An important limitation of precipitation sensors is contamination from ground clutter targets under conditions of anomalous propagation (AP). This problem can be mitigated significantly by high-pass clutter filters such as used by the Terminal Doppler Weather Radar (TDWR) and Next Generation Weather Radar (NEXRAD) systems....MIT Lincoln Laboratory (MIT/LL) has developed and tested an algorithm that removes AP from the NEXRAD reflectivity data. In this paper, we will first provide a brief description of the algorithm. Next we will present the truthing methodology used to identify AP. Then, we will show the algorithm performance results and failure mechanisms with this initial version. Finally, we consider refinements to improve the algorithm's performance.
Summary
An important limitation of precipitation sensors is contamination from ground clutter targets under conditions of anomalous propagation (AP). This problem can be mitigated significantly by high-pass clutter filters such as used by the Terminal Doppler Weather Radar (TDWR) and Next Generation Weather Radar (NEXRAD) systems....MIT Lincoln Laboratory (MIT/LL) has developed...
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The capabilities and limitations of using the ASR-9 as a terminal area precipitation sensor
September 7, 1997
Conference Paper
Published in:
28th Conf. on Radar Meteorology, 7-12 September 1997.
Summary
The Airport Surveillance Radar (ASR-9) weather channel is an invaluable tool to air-traffic and flight management specialists. The precipitation data from this sensor is currently displayed on air-traffic specialists' radar scopes and is incorporated into the Integrated Terminal Weather System (ITWS). The data are used to determine optimum routes for aircraft operating in and near the tenninal airspace. Data from other terminal area precipitation sensors such as the Terminal Doppler Weather Radar (TDWR) and the Next Generation Weather Radar (NEXRAD) are also used for this same purpose. The primary advantage of using the ASR-9 as a precipitation sensor is its high update rate, e.g. thirty seconds versus about five minutes for TDWR and N EX RAD. The ASR-9 is also quite reliable, with limited down time. Finally, range folding is not a significant problem with this radar. However, during ITWS prototype testing over the past three years, we have identified several limitations of using this radar as a precipitation sensor. For one, the maximum reflectivity of cells can be significantly underestimated by the ASR-9 due to partial filling of its fan-shaped elevation beam and cell-to-cell spatial averaging. Also, the occurrence of underestimation seems to increase when the radar operates in circular polarization mode. In addition, we have analyzed cases where significant precipitation-induced attenuation has occurred. Finally, because most ASR-9s are located on the airport, rain cores developing aloft, above the airport, maybe underestimated or missed entirely. This paper focuses on the problems identified through the ITWS prototype testing.
Summary
The Airport Surveillance Radar (ASR-9) weather channel is an invaluable tool to air-traffic and flight management specialists. The precipitation data from this sensor is currently displayed on air-traffic specialists' radar scopes and is incorporated into the Integrated Terminal Weather System (ITWS). The data are used to determine optimum routes for...
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The impact of thunderstorm growth and decay on air traffic management in class B airspace
February 2, 1997
Conference Paper
Published in:
7th Conf. on Aviation, Range, and Aerospace Meteorology, ARAM, 2-7 February 1997.
Summary
Air traffic management is a challenging task, especially if the airspace involved is impacted by inclement weather. The high volume of air traffic which inundates the nation's major airports compounds the difficulties with which Air Traffic Control (ATC) specialists have to cope. When you add the unpredictability of thunderstorm growth and decay to the controllers workload, air traffic management becomes even more of a challenge. ATC specialists would benefit from reliable forecasts of thunderstorm growth and decay. To determine how they would use a Growth and Decay product, ATC specialists from the Memphis Air Route Traffic Control Center (ARTCC), Traffic Management Unit (TMU), and TRACON supervisors were interviewed while viewing five movie loops of Memphis weather cases. The movies consisted of the ASR-9 six-level reflectivity data, aircraft beacons, and storm motion vectors.
Summary
Air traffic management is a challenging task, especially if the airspace involved is impacted by inclement weather. The high volume of air traffic which inundates the nation's major airports compounds the difficulties with which Air Traffic Control (ATC) specialists have to cope. When you add the unpredictability of thunderstorm growth...
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Discussion of the impact of data contamination on TDWR algorithm performance
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
Summary
The Federal Aviation Administration (FAA) is currently deploying Terminal Doppler Weather Radars (TDWRs) at key airports in the continental U.S. that experience high volumes of traffic and high frequencies of thunderstorm impact. The TDWR is designed to display the location and intensity of storm cells as well as the location and intensity of wind shear events in the airport vicinity. The TDWR system uses clutter filters and four data quality editing techniques: point target removal, clutter residue editing maps (CREMs), range obscuration editing, and velocity dealiasing in an attempt to reduce base data contamination prior to wind shear algorithm processing. The performance of the wind shear detection algorithms is directly related to the quality of the base data. In particular, failures of the data quality editors can seriously degrade the wind shear detection algorithm's performance. It will be shown that these failures can lead to both undetected and false events. In addition, clutter contamination from nonmeteorological sources such as birds can produce false wind shear signatures in the radar data. This paper will examine the impact of data contamination on algorithm performance at key TDWR sites where base and products data have been collected. The severity of these failures will be discussed, along with possible solutions to the most significant problems.
Summary
The Federal Aviation Administration (FAA) is currently deploying Terminal Doppler Weather Radars (TDWRs) at key airports in the continental U.S. that experience high volumes of traffic and high frequencies of thunderstorm impact. The TDWR is designed to display the location and intensity of storm cells as well as the location...
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