Publications
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...
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Wind shear detection using the Next Generation Airport Surveillance Radar
July 12, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-266
Summary
The Federal Aviation Administration (FAA) is deploying a Weather Systems Processor (WSP) for the current-generation Airport Surveillance Radar - ASR-9. This modification exploits the coherency of the ASR-9 to perform Doppler wind measurement. Signature recognition algorithms then automatically detect low altitude wind shear phenomena, track thunderstorm motion and display appropriate graphical and alphanumeric alerts to air traffic control (ATC) personnel. The FAA and U.S. Air Force are now procuring an ASR-11 to replace older terminal surveillance radars at facilities that did not receive the ASR-9. Although the antenna pattern, scan rate and energy-on-target of the ASR-11 match the corresponding parameters of the ASR-9, two other characteristics are markedly different. It utilizes a low peak power solid state transmitter that requires transmission of long, coded waveforms and a pulse compression receiver. Secondly, its pulse transmission sequence consists of short (five-pulse) bursts at both different pulse-repetition frequencies (PRF) and different RF frequencies. In this report, we assess the technical and operational issues associated with adding a WSP to the ASR-11. The existing WSP data processing and display technology are largely re-usable for the ASR-11 based WSP. Ground clutter filter coefficients and the length and number of coherent processing intervals would need to be changed to conform to the ASR-11 pulse transmission strategy, and straightforward adaptations to the equations used in the pulse-pair weather reflectivity and Doppler velocity estimation would be required. With these changes, the ASR-11 could host the WSP, subject to performance degradations for low reflectivity wind shear phenomena such as dry microbursts and gust fronts. A benefits assessment waas performed to evaluate the operational requirements for an ASR-11 based WSP. Given that the FAA has already committed to deploy improved Low Level Wind Shear Alert Systems (LLWAS) at most ASR-11 airports, the incremental safety benefits for the ASR-11 WSP appear to be less than the cost of the equipment. A case can be made for deployment based on "situational awareness" benefits that the WSP has been demonstrated to provide to air traffic controllers. We estimate that the value to the public and airline industry of reductions in aircraft delay, and avoidance of unnecessary diversions, would be in excess of eight million dollars per year tallied across 18 of the larger ASR-11 equipped airports.
Summary
The Federal Aviation Administration (FAA) is deploying a Weather Systems Processor (WSP) for the current-generation Airport Surveillance Radar - ASR-9. This modification exploits the coherency of the ASR-9 to perform Doppler wind measurement. Signature recognition algorithms then automatically detect low altitude wind shear phenomena, track thunderstorm motion and display appropriate...
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The behavior of total lightning activity in severe Florida thunderstorms
July 1, 1999
Journal Article
Published in:
Atmos. Res., Vol. 51, Nos. 3-4, July 1999, pp. 245-265.
Summary
The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier results for thunderstorm microbursts, the peak flash rate preceeds the severe weather at the ground by 5-20 min. A distinguishing feature of severe storms is the presence of lightning 'jumps' -- abrupt increases in flash rate in advance of the maximum rate for the storm. The systematic total lightning precursor to severe weather of all kinds -- wind, hail, tornadoes -- is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the intracloud lightning activity.
Summary
The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier...
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Comparisons of long-term Schumann resonance records in Europe and North America
June 7, 1999
Conference Paper
Published in:
11th Int. Conf. on Atmos. Electr. 7-11 June 1999, pp. 705-708.
Topic:
R&D area:
R&D group:
Summary
Two stations at a distance comparable with the wavelength in the Schumann resonance (SR) frequency range, one in Europe (Nagycenk, Hungary) and one in North America (West Greenwich, Rhode Island) have simultaneously monitored the natural vertical electric and horizontal magnetic field components in the frequency range of 3-25 Hz. This is a unique opportunity, as Schumann resonance stations are scarce and even fewer station have records with 5-6 year durations. The main purpose of this paper is to make comparisons in the SR time series measured simultaneously at the two field sites, thereby providing access to global behavior on the seasonal and interannual time scales. The comparative measurements described here point out distinct differences in the nature of convection in South America and in Africa, and reveal new aspects about the behavior of tropical continental convection on the ENS0 time scale.
Summary
Two stations at a distance comparable with the wavelength in the Schumann resonance (SR) frequency range, one in Europe (Nagycenk, Hungary) and one in North America (West Greenwich, Rhode Island) have simultaneously monitored the natural vertical electric and horizontal magnetic field components in the frequency range of 3-25 Hz. This...
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Schumann Resonances and the temporal-spatial dynamics of global thunderstorm activity
June 7, 1999
Conference Paper
Published in:
11th Int. Conf. on Atmospheric Electricity, 7-11 June 1999, pp. 698-700.
Summary
A two-dimensional computational ELF technique has been applied to interpret variations of peak frequencies of Schumann resosnances (SR) observed at the MIT experimental site (West Greenwich, Rhode Island). The spatial-temporal dynamics of global thunderstorm activity has been simulated on the basis of general meteorological data. It is shown that the proposed models provide a reasonable qualitative agreement between computed and observed variations for SR I to IV. Some inverse task diagrams has been constructed as an instrument for distinguishing between day-to-day thunderstorm scenarios.
Summary
A two-dimensional computational ELF technique has been applied to interpret variations of peak frequencies of Schumann resosnances (SR) observed at the MIT experimental site (West Greenwich, Rhode Island). The spatial-temporal dynamics of global thunderstorm activity has been simulated on the basis of general meteorological data. It is shown that the...
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The relationship between the background and transient signals in Schumann resonances
June 7, 1999
Conference Paper
Published in:
Proc. 11th Int. Conf. on Atmospheric Electricity, 7-11 June 1999, pp. 758-761.
Summary
Two distinct measures of the Earth's Schumann resonances -- the background and the transients -- are studied through comparisons at the mesoscale and at the continental scale. A rough proportionality is shown between the far more abundant afternoon lightning activity and the larger positive mesoscale discharges that make sprites and simultaneously ring the Earth- ionosphere cavity to levels higher than the integration of all other lightnings.
Summary
Two distinct measures of the Earth's Schumann resonances -- the background and the transients -- are studied through comparisons at the mesoscale and at the continental scale. A rough proportionality is shown between the far more abundant afternoon lightning activity and the larger positive mesoscale discharges that make sprites and...
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Total lightning activity associated with tornadic storms
June 7, 1999
Conference Paper
Published in:
11th Int. Conf. on Atmos. Electr., 7-11 June 1999, pp. 515-518.
Summary
Severe storms often have high flash rates (in excess of one flash per second) and are dominated by intracloud lightning activity. In addition to the extraordinary flash rates, there is a second distinguishing lightning characteristic of severe storms that seems to be important. When the total lightning history is examined, one finds sudden increases in the lightning rate, which we refer to as lightning "jumps", that precede the occurrence of severe weather by ten or more minutes. These jumps are typically 30-60 flashes/min, and are easily identified as anomalously large derivatives in the flash rate. This relationship is associated with updraft intensification and updraft strength is an important factor in storm severity (through the accumulation of condensate aloft and the stretching of vorticity). In several cases, evidence for diminishment of midlevel rotation and the descent of angular momentum from aloft is present prior to the appearance of the surface tornado. Based on our experience with severe and tornadic storms in Central Florida, we believe the total lightning may augment the more traditional use of NEXRAD radars and storm spotters. However, a more rigorous relation of these jumps to storm kinematics is needed if we are to apply total lightning in a decision tree that leads to improved warning lead times and decreased false alarm rates.
Summary
Severe storms often have high flash rates (in excess of one flash per second) and are dominated by intracloud lightning activity. In addition to the extraordinary flash rates, there is a second distinguishing lightning characteristic of severe storms that seems to be important. When the total lightning history is examined...
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Rotating a weather map
June 1, 1999
Journal Article
Published in:
Dr. Dobb's J., Vol. 24, No. 6, June 1999, pp. 80-88.
Summary
Introduction: I was recently part of a project developing a system for aircraft pilots to access the national ground weather-radar database while in flight. This weather-radar graphical database is generated from the outputs of the FAA and National Weather Service network of radars covering the continental United States and is updated every five minutes. Each pixel in the database covers a square measuring two kilometers (about one nautical mile) on a side. The content of each data pixel is a measure of the radar reflectivity measured at that location - radar reflectivity is proportional to the water content in the atmosphere (the precipitation rate). This graphical database is available through several commercial vendors - it's what you see displayed on The Weather Channel or during typical TV weather reports. Our system, on the other hand, provides a low-speed digital datalink connection from an FAA ground computer to an avionics computer/display located in the aircraft cockpit.
Summary
Introduction: I was recently part of a project developing a system for aircraft pilots to access the national ground weather-radar database while in flight. This weather-radar graphical database is generated from the outputs of the FAA and National Weather Service network of radars covering the continental United States and is...
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Review of NYC ITWS during the September 7, 1998 severe weather event
May 26, 1999
Project Report
Published in:
Project Report ATC-269, MIT Lincoln Laboratory
Summary
The New York City Integrated Terminal Weather System (ITWS) prototype became operational for the first time on August 30, 1998. Although this was near the end of the region's convective season, site staff were afforded a unique chance to assess the system's performance during Labor Day weekend on the afternoon of September 7 when a line of severe thunderstorms wreaked havoc over large areas of the Tri-state region. The storm with gusts reported as high as 80 mph, caused fatalities as boats overturned and trees fell on cars. Tornadoes were confirmed over New Jersey and Long Island, with major structural damage occurring in other areas as the result of strong straight-line winds and hail reported as large as 1.75 inches in diameter. Significant airport delays were experienced at the three major New York airports (over 600 flights delayed at least 15 minutes) and several hundred flights were cancelled. This report will assess the performance of ITWS and NEXRAD products during the time severe weather impacted the TRACON area, from about 1700 to 1930 UTC on September 7 (hereafter all times will be given in UTC). It will also discuss the synoptic weather setting and conclude with a section on the operational benefits users derived from ITWS on this day.
Summary
The New York City Integrated Terminal Weather System (ITWS) prototype became operational for the first time on August 30, 1998. Although this was near the end of the region's convective season, site staff were afforded a unique chance to assess the system's performance during Labor Day weekend on the afternoon...
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Lessons learned designing an alternative CHI for en route air traffic control
April 27, 1999
Conference Paper
Published in:
Controller Centered HMI, 27-29 April 1999.
Summary
MIT Lincoln Laboratory is supporting the FAA-sponsored effort to design an operationally suitable Computer Human Interface (CHI) for the recently upgraded En Route Air Traffic Control Centers. All centers will soon receive new control consoles with state-of-the-art 20 square (2K by 2K resolution) color displays (currently operating in Seattle as of January 1999). The future CHI is being modeled on Eurocontrol's Operational Display and Input Development (ODID) CHI, as requested by active controllers in the US. The ODID-like CHI, with its minimal information display and color coded guidance, provides increased efficiency and productivity through employment of a modern graphical user interface. Lessons learned during the on-going design process, including research of look and feel issues in conjunction with data analysis from controller-in-the-loop testing of a prototype ODID-like CHI will be discussed. The Laboratory plans to model the alternative ODID-like CHI on the best of the European ODID, Denmark Sweden Interface (DSI) and EATCHIP CHI features, while cognizant of the FAA?s DSR capabilities and limitations to support an improved user interface. Human factors issues need resolution to provide a consistent look and feel across the Free Flight Phase 1 products and platforms, the Center TRACON Automation System (CTAS) and the User Request Evaluation Tool (URET). MIT Lincoln Laboratory has built a CHI Requirements Engineering Model (CREM) to support controller-in-the-loop testing of the ODID-like CHI, validate CHI requirements and determine applicable standards for the design of an integrated CHI. The CREM provides a means to assess various CHI alternatives and the capability to iterate options with controller teams to address user concerns. Lessons learned from the ODID-like CHI specification process will also be shared.
Summary
MIT Lincoln Laboratory is supporting the FAA-sponsored effort to design an operationally suitable Computer Human Interface (CHI) for the recently upgraded En Route Air Traffic Control Centers. All centers will soon receive new control consoles with state-of-the-art 20 square (2K by 2K resolution) color displays (currently operating in Seattle as...
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