Publications
Detection probability modeling for airport wind-shear sensors
September 15, 2008
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-340
Summary
An objective wind-shear detection probability estimation model is developed for radar, lidar, and sensor combinations. The model includes effects of system sensitivity, site-specific wind-shear, clutter, and terrain blockage characteristics, range-aliased obscuration statistics, antenna beam filling and attenuation, and signal processing differences which allow a sensor- and site-specific performance analysis of deployed and future systems. A total of 161 sites are analyzed for the study, consisting of airports currently serviced by the Terminal Doppler Weather Radar (TDWR) (46), Airport Surveillance Radar Weather Systems Processor (ASR-9 WSP) (35), Low Altitude Wind Shear Alert System-Relocation/Sustainment (LLWAS-RS) (40), and no wind-shear detection system (40). Sensors considered are the TDWR, WSP, LLWAS, Weather Surveillance Radar 1988-Doppler (WSR-88D, commonly known as NEXRAD), adn the Lockheed Martin Coherent Technologies (LMCT) Doppler lidar and proposed x-band radar. [not complete]
Summary
An objective wind-shear detection probability estimation model is developed for radar, lidar, and sensor combinations. The model includes effects of system sensitivity, site-specific wind-shear, clutter, and terrain blockage characteristics, range-aliased obscuration statistics, antenna beam filling and attenuation, and signal processing differences which allow a sensor- and site-specific performance analysis of...
READ MORE
Comparative analysis of terminal wind-shear detection systems
January 20, 2008
Conference Paper
Published in:
13th Conf. on Aviation, Range and Aerospace Meteorology, ARAM, 20-24 January 2008.
Summary
Low-level wind shear, especially a microburst, is very hazardous to aircraft departing or approaching an airport. The danger became especially clear in a series of fatal commercial airliner accidents in the 1970s and 1980s at U.S. airports. In response, the Federal Aviation Agency (FAA) developed and deployed three ground-based low-altitude wind-shear detection systems: the Low Altitude Wind Shear Alert System (LLWAS) (Wilson and Gramzow 1991), the Terminal Doppler Weather Radar (TDWR) (Michelson et al. 1990), and the Airport Surveillance Radar Weather Systems Processor (ASR-9 WSP) (Weber and Stone 1995). Since the deployment of these sensors, commercial aircraft wind-shear accidents have dropped to near zero in the U.S. This dramatic decrease in accidents caused by wind shear appears to confirm the safety benefits provided by these detection systems. In addition, the broad area measurement capability of the TDWR and WSP provides ancillary delay reduction benefits, for example, by forecasting airport wind shifts that may require runway reconfiguration. The current deployment strategy for these various windshear detection systems is justified by an earlier integrated wind-shear systems cost-benefit analysis (Martin Marietta 1994). Since that time, conditions in the national airspace system (NAS) have evolved, such as the installation of onboard predictive wind-shear detection systems in an increasing number of aircraft, improved pilot training for wind-shear hazard identification, avoidance, and recovery, and further integration of observed wind-shear data into terminal weather systems. Given the tight fiscal environment at the FAA in recent years, the cost of maintaining the wind-shear detection systems has also become an issue. All systems require periodic service life extension programs (SLEPs). In light of these developments, the FAA has tasked MIT Lincoln Laboratory to provide an updated cost-benefit study on their terminal wind-shear detection systems. One of the key factors in estimating the benefits of a terminal wind-shear detection system is its performance. Thus, it is necessary to quantify the wind-shear detection probability for each sensor, preferably on an airport-by-airport basis. To consider sensors that are not yet deployed, a model must be developed that takes into account the various effects that factor into the detection probability. We have developed such a model. The focus of this paper is on this model and the results obtained with it.
Summary
Low-level wind shear, especially a microburst, is very hazardous to aircraft departing or approaching an airport. The danger became especially clear in a series of fatal commercial airliner accidents in the 1970s and 1980s at U.S. airports. In response, the Federal Aviation Agency (FAA) developed and deployed three ground-based low-altitude...
READ MORE
An automated visibility detection algorithm utilizing camera imagery
January 14, 2007
Conference Paper
Published in:
87Th AMS Annual Meeting, 14-18 January 2007.
Summary
The Federal Highway Administration (FHWA) has had a focused program to improve the integration of weather decision support systems into surface transportation operations since 1999. Clarus (Latin for clear) is the FHWA's most recent surface transportation weather initiative. The Clarus concept is to develop and demonstrate an integrated surface transportation weather observing, forecasting and data management system (Pisano, 2006a). As part of this effort, the FHWA is also promoting research into methods for applying new and existing sensor or probe data. These efforts include utilizing new in-vehicle sensor data that will be part of the vehicle infrastructure initiative (VII) (Pisano, 2006b), and finding innovative ways to use existing camera imagery. MIT Lincoln Laboratory (MIT/LL) was tasked to evaluate the usefulness of camera imagery for sensing ambient and road weather conditions and the feasibility for creating a portable visibility estimation algorithm. This paper gives a general background on the current utilization of camera imagery, including past and ongoing research of automated weather/condition algorithms. This is followed by a description of the MIT/LL camera test site, the analyses performed and the resultant prototype visibility estimation algorithm. In addition, the paper details application of the prototype algorithm to existing state DOT cameras in Utah. The final section discusses the future possibilities of camera-based weather and road condition algorithms.
Summary
The Federal Highway Administration (FHWA) has had a focused program to improve the integration of weather decision support systems into surface transportation operations since 1999. Clarus (Latin for clear) is the FHWA's most recent surface transportation weather initiative. The Clarus concept is to develop and demonstrate an integrated surface transportation...
READ MORE
SFO marine stratus forecast system documentation
October 17, 2006
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-319
Summary
San Francisco International Airport (SFO) experiences frequent low ceiling conditions during the summer season due to marine stratus clouds. Stratus in the approach zone prevents dual approaches to the airport??s closely spaced parallel runways, effectively reducing arrival capacity by half. The stratus typically behaves on a daily cycle, with dissipation occurring during the hours following sunrise. Often the low ceiling conditions persist throughout the morning hours and interfere with the high rate of air traffic scheduled into SFO from mid-morning to early afternoon. Air traffic managers require accurate forecasts of clearing time to efficiently administer Ground Delay Programs (GDPs) to match the rate of arriving aircraft with expected capacity. The San Francisco Marine Stratus Forecast System was developed as a tool for anticipating the time of stratus clearing. The system relies on field-deployed sensors as well as routinely available regional surface observations and satellite data from the Geostationary Operational Environmental Satellite (GOES-West). Data are collected, processed, and input to a suite of forecast models to predict the time that the approach zone will be sufficiently clear to perform dual approaches. Data observations and model forecasts are delivered to users on an interactive display accessible via the Internet. The system prototype was developed under the sponsorship of the FAA Aviation Weather Research Program (AWRP). MIT Lincoln Laboratory served as technical lead for the project, in collaboration with San Jose State University, the University of Quebec at Montreal, and the Center Weather Service Unit (CWSU) at the Oakland Air Route Traffic Control Center (ARTCC). The National Weather Service (NWS), under the direction of the NWS Forecast Office in Monterey, assumed responsibility for operation and maintenance of the system following technical transfer in 2004. This document was compiled as a resource to support continuing system operation and maintenance.
Summary
San Francisco International Airport (SFO) experiences frequent low ceiling conditions during the summer season due to marine stratus clouds. Stratus in the approach zone prevents dual approaches to the airport??s closely spaced parallel runways, effectively reducing arrival capacity by half. The stratus typically behaves on a daily cycle, with dissipation...
READ MORE
Automated extraction of weather variables from camera imagery
August 18, 2005
Conference Paper
Published in:
Proc. of 2005 Mid-Continent Transportation Research Symp., 18-19 August 2005.
Summary
Thousands of traffic and safety monitoring cameras are deployed or are being deployed all across the country and throughout the world. These cameras serve a wide range of uses from monitoring building access to adjusting timing cycles of traffic lights at clogged intersections. Currently, these images are typically viewed on a wall of monitors in a traffic operations or security center where observers manually monitor potentially hazardous or congested conditions and notify the appropriate authorities. However, the proliferation of camera imagery taxes the ability of the manual observer to track and respond to all incidents. In addition, the images contain a wealth of information, including visibility, precipitation type, road conditions, camera outages, etc., that often goes unreported because these variables are not always critical or go undetected. Camera deployments continue to expand and the corresponding rapid increases in both the volume and complexity of camera imagery demand that automated algorithms be developed to condense the discernable information into a form that can be easily used operationally by users. MIT Lincoln Laboratory (MIT/LL) under funding from the Federal Highway Administration (FHWA) is investigating new techniques to extract weather and road condition parameters from standard traffic camera imagery. To date, work has focused on developing an algorithm to measure atmospheric visibility and prove the algorithm concept. The initial algorithm examines the natural edges within the image (the horizon, tree lines, roadways, permanent buildings, etc) and performs a comparison of each image with a historical composite image. This comparison enables the system to determine the visibility in the direction of the sensor by detecting which edges are visible and which are not. A primary goal of the automated camera imagery feature extraction system is to ingest digital imagery with limited specific site information such as location, height, angle, and visual extent, thereby making the system easier for users to implement. There are, of course, many challenges in providing a reliable automated estimate of the visibility under all conditions (camera blockage/movement, dirt/raindrops on lens, etc) and the system attempts to compensate for these situations. This paper details the work-to-date on the visibility algorithm and defines a path for further development of the overall system.
Summary
Thousands of traffic and safety monitoring cameras are deployed or are being deployed all across the country and throughout the world. These cameras serve a wide range of uses from monitoring building access to adjusting timing cycles of traffic lights at clogged intersections. Currently, these images are typically viewed on...
READ MORE
Automated forecasting of road conditions and recommended road treatments for winter storms
February 9, 2003
Conference Paper
Published in:
19th Int. Conf. of Interactive Information Processing Systems for Meteorology, Oceanography and Hydrology, 9-13-February 2003.
Summary
Over the past decade there have been significant improvements in the availability, volume, and quality of the sensors and technology utilized to both capture the current state of the atmosphere and generate weather forecasts. New radar systems, automated surface observing systems, satellites and advanced numerical models have all contributed to these advances. However, the practical application of this new technology for transportation decision makers has been primarily limited to aviation. Surface transportation operators, like air traffic operators, require tailored weather products and alerts and guidance on recommended remedial action (e.g. applying chemicals or adjusting traffic flow). Recognizing this deficiency, the FHWA (Federal Highway Administration) has been working to define the weather related needs and operational requirements of the surface transportation community since October 1999. A primary focus of the FHWA baseline user needs and requirements has been winter road maintenance personnel (Pisano, 2001). A key finding of the requirements process was that state DOTs (Departments of Transportation) were in need of a weather forecast system that provided them both an integrated view of their weather, road and crew operations and advanced guidance on what course of action might be required to keep traffic flowing safely. As a result, the FHWA funded a small project (~$900K/year) involving a consortium of national laboratories to aggressively research and develop a prototype integrated Maintenance Decision Support System (MDSS). The prototype MDSS uses state-of-the-art weather and road condition forecast technology and integrates it with FHWA anti-icing guidelines to provide guidance to State DOTs in planning and managing winter storm events (Mahoney, 2003). The overall flow of the MDSS is shown in Figure 1. Basic meteorological data and advanced models are ingested into the Road Weather Forecast System (RWFS). The RWFS, developed by the National Center for Atmospheric Research (NCAR), dynamically weights the ingested model and station data to produce ambient weather forecasts (temperature, precipitation, wind, etc.). More details on the RWFS system can be found in (Myers, 2002). Next, the RCTM (Road Condition Treatment Module) ingests the forecasted weather conditions from the RWFS, calculates the predicted road conditions (snow depth, pavement temperature), Once a treatment plan has been determined, the recommendations are presented in map and table form through the MDSS display. The display also allows users to examine specific road and weather parameters, and to override the algorithm recommended treatments with a user-specified plan. A brief test of the MDSS system was performed in Minnesota during the spring of 2002. Further refinements were made and an initial version of the MDSS was released by the FHWA in September 2002. While this basic system is not yet complete, it does ingest all the necessary weather data and produce an integrated view of the road conditions and recommended treatments. This paper details the RCTM algorithm and its’ components, including the current and potential capabilities of the system.
Summary
Over the past decade there have been significant improvements in the availability, volume, and quality of the sensors and technology utilized to both capture the current state of the atmosphere and generate weather forecasts. New radar systems, automated surface observing systems, satellites and advanced numerical models have all contributed to...
READ MORE
A web-based display and access point to the FAA's Integrated Terminal Weather System (ITWS)
May 13, 2002
Conference Paper
Published in:
10th Conf. on Aviation, Range and Aerospace Meteorology, 13-16 May 2002, pp. 206-209.
Summary
The Integrated Terminal Weather System (ITWS) is a high-resolution weather information system designed to operate within the TRACONs surrounding the country's major airports. Targeted for those airports most often adversely affected by convective weather, the system was developed for the Federal Aviation Administration (FAA) by the Massachusetts Institute of Technology's Lincoln Laboratory (MIT/LL) Weather Sensing Group. The ITWS acquires data from Next Generation Radars (NEXRAD), Terminal Doppler Weather Radars (TDWR), Airport Surveillance Radars (ASR-9), Low Level Windshear Alert Systems (LLWAS), the National Lightning Detection Network (NLDN), Automated Weather Observing Stations (AWOS/ASOS), and aircraft in flight. The system integrates the data to provide consistent weather information in a form that is usable without further meteorological interpretation. This information includes six-level precipitation at a number of ranges, windshear and microburst detection and prediction, storm motion and extrapolated position, wind fields, gust fronts, lightning, and storm cell information (hail, mesocyclone notification, and echo tops). A set of direct users of ITWS (FAA users at TRACONs, Air Traffic Control Towers, and en-route centers) will receive ITWS weather products through FAA-provided Situation Displays (SDs) that are tied directly to the ITWS processor. In addition, the FAA has sponsored development of an ITWS External Users Data Distribution System to provide real-time ITWS products to those users who do not have access to a dedicated SD. The data distribution system is being developed in conjunction with the upcoming deployment of the ITWS (2002-2004) as an operational FAA system serving 47 major airports. The need for a remotely accessible display is strongly supported by draft recommendations recently released by the National Transportation Safety Board (NTSB) that call for U.S. air carriers and all air traffic control facilities to have access to data from FAA terminal weather information systems. In addition, the Collaborative Decision Making program (CDM) has highlighted the need to make the information widely available to airlines. MIT/LL has operated demonstration ITWS systems since 1994, and a demonstration website since 1997. Most major airlines have successfully accessed the ITWS demonstration products in real time via Web browsers and have used this information to improve safety and reduce delays (Maloney, 2000). Benefits specific to airline dispatch include support for decisions made during diversion situations and improvements in hub operations . By sharing a common view of the same operational environment, controllers, dispatchers and other aviation decision makers and stakeholders have been better able to understand and coordinate the decisions that affect air traffic in the terminal area and surrounding en route airspace (Evans 2000). This paper describes the goals of the ITWS External Users Data Distribution System development project, including a discussion of the system architecture, data distribution and access methods, and the web-based interface.
Summary
The Integrated Terminal Weather System (ITWS) is a high-resolution weather information system designed to operate within the TRACONs surrounding the country's major airports. Targeted for those airports most often adversely affected by convective weather, the system was developed for the Federal Aviation Administration (FAA) by the Massachusetts Institute of Technology's...
READ MORE
TCWF algorithm assessment - Memphis 2000
July 9, 2001
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-297
Summary
This report describes a formal Assessment of the Terminal Convective Weather Forecast (TCWF) algorithm, developed under the FAA Aviation Weather Research Program by MIT Lincoln Laboratory as part of the Convective Weather Product Development Team (PDT). TCWF is proposed as a Pre-Planned Product Improvement (P3I) enhancement to the operational ITWS currently scheduled for deployment at major airports in 2002. The TCWF Assessment in Memphis, TN ran from 24 March to 30 September 2000. The performance of TCWF was excellent on the large scale, organized storm systems it was designed to predict, and the software was extremely stable during the Assessment. Small changes to the algorithm parameters were made as a result of the 2000 testing. The TCWF performance can be improved on airmass storms and on forecasting new growth and subsequent decay of large-scale storms. These are active areas of research for future ITWS P3I builds.
Summary
This report describes a formal Assessment of the Terminal Convective Weather Forecast (TCWF) algorithm, developed under the FAA Aviation Weather Research Program by MIT Lincoln Laboratory as part of the Convective Weather Product Development Team (PDT). TCWF is proposed as a Pre-Planned Product Improvement (P3I) enhancement to the operational ITWS...
READ MORE
FAA terminal convective weather forcast algorithm assessment
September 11, 2000
Conference Paper
Published in:
Ninth Conf. on Aviation, Range, and Aerospace Meteorology, 11-15 September 2000, pp. 365-370.
Summary
Air traffic delay due to convective weather reached historically high levels in 1999, as passengers blamed airlines and airlines blamed the FAA for the massive inconveniences. While coordination between the FAA's System Command Center and the regional centers and terminals can be expected to improve with the FAA's new initiatives, it is clear that air traffic management and planning during convective weather will ultimately require accurate convective weather forecasts. In addition to improving system capacity and reducing delay, convective forecasts can help provide safer flight routes as well. The crash of a commercial airliner at Little Rock, AR in June 1999 after a one-hour flight from Dallas/Ft. Worth illustrates the dangers and potential tactical advantage that could be gained with frequently updated one-hour forecasts of convective storms. The Terminal Convective Weather Forecast (TCWF) product has been developed by MIT Lincoln Laboratory as part of the FAA Aviation Weather' Research Convective Weather Product Development Team (PDT). Lincoln began by consulting with air traffic personnel and commercial airline dispatchers to determine the needs of aviation users (Forman, et. al., 1999). Users indicated that convective weather, particularly line storms, caused the most consistent problems for managing air traffic. The "Growth and Decay Storm Tracker" developed by Wolfson et al. (1999) allows the generation of up to 1-hour forecasts of large scale, organized precipitation features with operationally useful accuracy. This patented technology. represents a breakthrough in short-term forecasting capability, providing quantitative envelope tracking as opposed to the usual cell tracking. This tracking technology is now being utilized in NCAR's AutoNowcaster (Mueller, et al., 2000), the National Convective Weather Forecast running at the Aviation Weather Center (Megenhardt, et al., 2000) and by private sector meteorological data vendors. The TCWF has been tested in Dallas/Ft. Worth (DFW) since 1998, in Orlando (MCO) since 1999, and in New York (NYC) since fiscal year 2000 began. These have been informal demonstrations, with the FAA William J. Hughes Technical Center (WJHTC) assessing utility to the users, and with MIT LL modifying the system based on user feedback and performance analyses. TCWF has undergone major revisions, and the latest build has now been deployed at all sites. The TCWF is now in a formal assessment phase at the Memphis international Airport as a prerequisite to an FAA operational requirement. The FAA Technical Center will make a recommendation on whether TCWF is suitable for inclusion in the FAA's operational integrated Terminal Weather System (ITWS), which has an unmet requirement for 30+ minute forecasts of convective weather. Memphis was selected for the TCWF Assessment since it has not been exposed to the forecast product during prior demonstrations. Operations began on March 24, 2000 and operational feedback is being assessed by the FAA Technical Center (McGettigan, et al., 2000) and MCR Corporation is performing a quantitative benefits assessment (Sunderlin and Paull, 2000). This paper details the refined TCWF algorithm and display concept, gives examples of the operational impact of terminal forecasts, and analyzes the technical performance of the TCWF during the early stages of the Memphis Assessment.
Summary
Air traffic delay due to convective weather reached historically high levels in 1999, as passengers blamed airlines and airlines blamed the FAA for the massive inconveniences. While coordination between the FAA's System Command Center and the regional centers and terminals can be expected to improve with the FAA's new initiatives...
READ MORE
The FAA Terminal Convective Weather Forecast product: scale separation filter optimization
July 12, 1999
Conference Paper
Published in:
29th Int. Conf. on Radar Meteorology, 12-16 July 1999.
Summary
A large percentage of serious air traffic delay at major airports in the warm season is caused by convective weather. The FAA Convective Weather Product Development team (PDT) has developed a Terminal Convective Weather Forecast product (TCWF) that can account for short-term (out to 60 min) systematic growth and decay of thunderstorms. The team began work three years ago by evaluating air traffic user needs and requirements. We found that users were willing to trade off forecast accuracy for longer lead times, especially for air traffic management plans that were easy to implement or that incurred low risk (Forman, et al., 1999). The PDT was able to develop an operationally useful forecast product that has been demonstrated in Dallas, TX since March, 1998 (Hallowell, et al., 1999). Further improvements have been made, and testing is now taking place at both Dallas and Orlando, FL. This paper summarizes the basic algorithm methodology and presents quantitative results on optimization of the scale separation filter, which is an integral aspect of the forecast algorithm.
Summary
A large percentage of serious air traffic delay at major airports in the warm season is caused by convective weather. The FAA Convective Weather Product Development team (PDT) has developed a Terminal Convective Weather Forecast product (TCWF) that can account for short-term (out to 60 min) systematic growth and decay...
READ MORE