Publications
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...
READ MORE
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...
READ MORE
The Memphis ITWS convective forecasting collaborative demonstration
February 2, 1997
Conference Paper
Published in:
7th Conf. on Aviation, Range, and Aerospace Meteorology, ARAM, 2-7 February 1997.
Summary
Accurate, short-term forecasts of where thunderstorms will develop, move and decay allow for strategic traffic management in and around the aviation terminal and enroute airspace. Pre-planning to avoid adverse weather conditions provides safe, smooth and continuous air traffic flow and savings in both fuel cost and time. Wolfson, et. al ( 1997) describe the problem of convective weather forecasting for FAA applications. In 1995, National Center for Atmospheric Research (NCAR), MIT Lincoln Laboratory (MIT-LL) and National Severe Storms Laboratory (NSSL) scientists and engineers agreed to collaborate on the development of a convective weather forecasting algorithm for use in airport terminal areas. Each laboratory brings special strengths to the project. NCAR has been developing techniques for precise, short-term (0-60 minutes) forecasts of thunderstorm initiation, movement and dissipation for the FAA over the past ten years and has developed the Auto-Nowcaster software. MIT-LL has been developing real-time algorithms for the Integrated Terminal Weather System (ITWS), including techniques for storm tracking, gust front detection, and calculating storm growth and decay (as part of predicting microbursts) . NSSL has been working on the NEXRAD Storm Cell Identification and Tracking (SCIT) algorithm, and on understanding the predictive value of the storm cell information. Thus by using the latest research results and best techniques available at each laboratory, the collaborative effort will hopefully result in a superior convective weather forecasting algorithm. Our goal in the immediate future is to develop a joint algorithm that can be demonstrated to users of terminal weather information, so that the benefits of convective weather forecast information can be realized, and the remaining needs can be assessed. As a first effort in the collaboration, the laboratories fielded their individual algorithms at the Memphis ITWS site. This paper gives an overview of our collaborative experiment in Memphis, the system each laboratory operated, some preliminary analysis of our performance on one case, and our plans for the near future.
Summary
Accurate, short-term forecasts of where thunderstorms will develop, move and decay allow for strategic traffic management in and around the aviation terminal and enroute airspace. Pre-planning to avoid adverse weather conditions provides safe, smooth and continuous air traffic flow and savings in both fuel cost and time. Wolfson, et. al...
READ MORE
Report on product performance for the Terminal Doppler Weather Radars (TDWRs) at Washington National Airport and Memphis and Orlando International Airports
January 29, 1997
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-246
Summary
Massachusetts Institute of Technology Lincoln Laboratory provides support to the Terminal Doppler Weather Radar (TDWR) Program Office in the performance analysis of deployed TDWR systems, and resulting recommendations for systems enhancements. This report documents initial performance of the TDWR products at Washington National Airport (DCA), Memphis International Airport (MEM) and Orlando International Airport (MCO). This performance depends, in turn, on the site optimization performed for the specific radars. Therefore, an overview of site optimization process, using DCA as a concrete example, is included. After the sites were optimized, base data (Doppler velocity and reflectivity) and product data (algorithm detections) were collected to assess the quality of the base data and the performance of the microburst and gust front detection algorithms. It is assumed that the reader of this report has an extensive knowledge of the TDWR system. (Not Complete)
Summary
Massachusetts Institute of Technology Lincoln Laboratory provides support to the Terminal Doppler Weather Radar (TDWR) Program Office in the performance analysis of deployed TDWR systems, and resulting recommendations for systems enhancements. This report documents initial performance of the TDWR products at Washington National Airport (DCA), Memphis International Airport (MEM) and...
READ MORE
Analysis of the 12 April 1996 wind shear incident at DFW airport
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
Summary
Wind shear detection algorithms that operate on Doppler radar data are tuned to primarily recognize the velocity and reflectivity signatures associated with microbursts and gust fronts. Microbursts produce a divergent pattern in the velocity field that is associated with a descending column of precipitation. Gust fronts produce a convergent pattern that is often associated with a thin-line reflectivity feature. On April 12, 1996 at Dallas-Fort Worth International Airport (DFW) three pilots reported encounters with wind shear in a five minute period (2329-33 GMT). The third pilot (AA 1352) reported an encounter with "severe wind shear", which we refer to as "the incident" throughout the paper. He used maximum throttle to keep the MD-80 in the air and reported that it was only "by the grace of God" that the aircraft did not crash (Dallas Morning News, 4/19/96). The plane, originally bound for Pittsburgh, was diverted to Tulsa where the passengers were offloaded to another aircraft, the black box was removed, and the engines were checked according to procedures required whenever maximum throttle is utilized.
Summary
Wind shear detection algorithms that operate on Doppler radar data are tuned to primarily recognize the velocity and reflectivity signatures associated with microbursts and gust fronts. Microbursts produce a divergent pattern in the velocity field that is associated with a descending column of precipitation. Gust fronts produce a convergent pattern...
READ MORE
Comparison of the performance of the Integrated Terminal Weather System (ITWS) and Terminal Doppler Weather Radar (TDWR) microburst detection algorithms
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
Summary
This paper describes the designs of the TDWR and ITWS Microburst Detection algorithms, and compares their performances in the Orlando, FL and Memphis, TN environments. This is the first study in which the performance of the TDWR and ITWS microburst detection algorithms are compared using an identical data set and a common set of truth criteria. Examples are presented illustrating common scenarios which create the performance differences. Detail is presented on the impact of the ITWS VIL (Vertically Integrated Liquid water) test in reducing algorithm false alarms. This algorithm feature is currently being considered as a retrofit to the TDWR algorithm.
Summary
This paper describes the designs of the TDWR and ITWS Microburst Detection algorithms, and compares their performances in the Orlando, FL and Memphis, TN environments. This is the first study in which the performance of the TDWR and ITWS microburst detection algorithms are compared using an identical data set and...
READ MORE
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...
READ MORE
Comparative analysis of ground-based wind shear detection radars
May 8, 1995
Conference Paper
Published in:
Proc. IEEE 1995 Int. Radar Conf., 8-11 May 1995, pp. 486-495.
Summary
The UNISYS Corporation has developed a microburst prediction radar (MBPR) to provide detection and short-term predictions of the most hazardous form of low altitude wind shear in the vicinity of an airport. The MBPR is intended for deployment on- or near-airport so as to minimize range coverage (and associated radar power-aperture) requirements. Like the airport surveillance radar wind shear processor (ASR-WSP), the cost of the MBPR is significantly less than that of the terminal Doppler weather radar (TDWR) so that its deployment at smaller airports might be economically justified if the performance is operationally acceptable. Field tests of engineering prototypes of the MBPR have been conducted in conjunction with FAA-sponsored TDWR and WSP demonstration programs. We assess the capabilities and limitations of each of these systems using a consistent methodology that emphasizes the comparative analysis of the significant parameters of each radar in relation to wind shear phenomenology. An extensive database on wind shear event radar cross section, spatial structure and intensity distribution-derived through our FAA-sponsored testing of TDWR and ASR-WSP prototypes is an important asset in developing this comparison.
Summary
The UNISYS Corporation has developed a microburst prediction radar (MBPR) to provide detection and short-term predictions of the most hazardous form of low altitude wind shear in the vicinity of an airport. The MBPR is intended for deployment on- or near-airport so as to minimize range coverage (and associated radar...
READ MORE
Preliminary results of the weather testing component of the Terminal Doppler Weather Radar operational test and evaluation
May 24, 1993
Conference Paper
Published in:
Proc. 26th Int. Conf. on Radar Meteorology, 24-28 May 1993, pp. 29-34.
Summary
The Terminal Doppler Weather Radar (TDWR) system which has been developed by Raytheon Co. for the Federal Aviation Administration (FAA), provides automatic detection of microbursts and low-altitude wind shear. Microburst- and gust front-induced wind shear can result in a sudden, large change in airspeed which can have disastrous effect on aircraft performance. during take off or landing. The second major function of TDWR is to improve air traffic management through forecasts of wind shifts, precipitation and other weather hazards. The TDWR system generates Doppler velocity, reflectivity, and spectrum width data. The base data are automatically dealiased and clutter is removed through filtering and mapping. Precipitation and windshear products, such as microbursts and gust fronts, are displayed as graphic products on the Geographic Situation Display which is intended for use by Air Traffic Control supervisors. Alphanumeric messages indicating the various windshear alerts and derived airspeed losses and gains are sent to a flat panel ribbon display which is used by the controllers in the control tower. The TDWR proof-of-concept and operational feasibility have been demonstrated in a number of FAA-sponsored tests and evaluations conducted by Massachusetts Institute of Technology's Lincoln Laboratory (MIT/LL) in Memphis, TN (1985); Huntsville, AL (1986); Denver, CO (1987, 1988); Kansas City, MO (1989, and Orlando, FL (1990-1992). In order to verify that the TDWR meets FAA operational suitability and effectiveness requirements, an Operational Test & Evaluations (OT&E) was conducted at the Oklahoma City site during the period from 24 August to 30 October 1992. The testing addressed National Airspace System (NAS)-SS-1000 requirements, weather detection performance, safety, operational system performance, maintenance, instruction books, Remote Maintenance Monitoring System (RMMS), system adaptable parameters, bullgear wear, and limited Air Traffic (AT) suitability. The TDWR OT&E Integration and Operational testing was conducted using a variety of methods dependent on the area being tested. This paper discusses primarily the weather detection performance testing. A rough analysis was performed on the algorithm output and the base data to determine the performance of the TDWR in detecting wind shear phenomena. Final results will be available after additional testing, which is scheduled for Spring of 1993, and post analysis in conducted.
Summary
The Terminal Doppler Weather Radar (TDWR) system which has been developed by Raytheon Co. for the Federal Aviation Administration (FAA), provides automatic detection of microbursts and low-altitude wind shear. Microburst- and gust front-induced wind shear can result in a sudden, large change in airspeed which can have disastrous effect on...
READ MORE
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...
READ MORE