Publications
Optimizing the ITWS algorithm designed to remove anomalous propagation ground clutter from the ASR-9 precipitation product
January 10, 1999
Conference Paper
Published in:
8th Conf. on Aviation, Range and Aerospace Meteorology, ARAM, 10-15 January 1999.
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Summary
A key product within the Integrated Terminal Weather System (ITWS) Initial Operating Capability (IOC) product suite removes anomalous propagation (AP) ground clutter from the ASR-9 precipitation product. This has been identified as a critical component of ITWS due to the frequent occurrence of AP when storms or outflows move over an ASR-9. Editing is accomplished by comparing the raw ASR-9 weather data to composite maps generated by the Next Generation Weather Radar (NEXRAD) and the Terminal Doppler Weather Radar (TDWR). An editing template, containing regions of AP, is created based on the ASR-9 data collected at the middle of the composite volume scan to minimize the difference in update rates. The template is used to edit the ASR-9 scan immediately after the composite map and all subsequent scans until a new composite map is received. This algorithm has been shown to perform quite well, especially if the weather and AP returns are not co-located. During the 1994 Demonstration and Validation Operational Test and Evaluation in Memphis (MEM) and Orlando (MCO), the probability of editing AP (PEAP) in the absence of weather was 0.97 for level 2 and greater returns (Klingle-Wilson, 1995). The probability of editing weather (PEW) for those cases with weather only was quite low, i.e., 0.01. In order to minimize the removal of weather returns in those cases where the AP and weather are located in close proximity, the editing thresholds are quite conservative. This is reflected by the 1994 results which show a PEAP of 0.81 and a PEW of 0.02 for this class of event. Besides the conservative thresholds, another area of concern is the fact that the AP regions can expand or increase in intensity after the AP editing template is created. This rapid variation frequently occurs with convectively generated AP and can cause the performance of the algorithm to decrease with time until a new template is created. In this study, we will examine the algorithm failure mechanisms in detail to identify possible site-adaptable parameter changes that can be used to improve the performance for the mixed weather/AP events. This is especially germane since the parameter set was not re-evaluated after the TDWR composite map was incorporated in 1995. In the critical region over the airport during hazardous weather conditions, this radar updates more frequently than the NEXRAD. Since the parameters were designed to account for the NEXRAD volume update rate, they are probably too conservative for the current algorithm (which uses both composite maps).
Summary
A key product within the Integrated Terminal Weather System (ITWS) Initial Operating Capability (IOC) product suite removes anomalous propagation (AP) ground clutter from the ASR-9 precipitation product. This has been identified as a critical component of ITWS due to the frequent occurrence of AP when storms or outflows move over...
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Total global lightning inferred from Schumann resonance measurements
December 27, 1998
Journal Article
Published in:
J. Geophys. Res., Vol. 103, No. D24, 27 December 1998, pp. 31,775-31,779.
Summary
Radiation with frequencies of 5-30 Hz is ducted between Earth's surface and ionosphere with little attenuation; at the lowest frequencies, waves travel several times around the Earth before losing most of their energy. Much of this radiation is produced by lightning. Here we assume that all of this radiation is produced by lightning, and attempt to invert the observed and electric and magnetic fields to infer global lightning activity. We show 10 days of inversions. For these 10 days, the inferred average rate of vertical charge transfer squared is only 1.7 105 (ten to the fifth) (Ckm)2/s Other studies suggest that the root mean square moment change of a flash is about 166 Coulomb kilometers. If we naively assume that each of these flashes is composed of four equally sized strokes, then we conclude that our entire observed signal could be produced by only 22 flashes per second.
Summary
Radiation with frequencies of 5-30 Hz is ducted between Earth's surface and ionosphere with little attenuation; at the lowest frequencies, waves travel several times around the Earth before losing most of their energy. Much of this radiation is produced by lightning. Here we assume that all of this radiation is...
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En route ATM decision support tool computer-human interface requirements development
December 1, 1998
Conference Paper
Published in:
2nd USA/Europe Air Traffic Management R&D Seminar, 1-4 December 1998.
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MIT Lincoln Laboratory (MIT/LL) is supporting the FAA-sponsored effort to specify Computer Human Interface (CHI) requirements for the En Route Air Traffic Management Decision Support Tools (ERATMDST) program. The ERATMDST CHI specification is the FAA's vehicle to ensure an operationally suitable user interface is provided for the DSTs (such as conflict probe) to support free flight. The initial draft of the ERATMDST CHI requirements was published in September 1998 and defines an initial CHI which incorporates elements of the NASA CTAS and the MITRE URET prototypes, an Operational Display and Input Development (ODID) display philosophy, and an outline of the end-state CHI. The information will be presented with a consistent, usable look and feel modeled on the advanced human-centered CHI developed by Eurocontrol. This paper describes a CHI Requirements Engineering Model (CREM) and presents preliminary test results of ODID-like display elements in the ERATMDST CHI with controller-in- the-loop simulations presented in terms of workload and response times.
Summary
MIT Lincoln Laboratory (MIT/LL) is supporting the FAA-sponsored effort to specify Computer Human Interface (CHI) requirements for the En Route Air Traffic Management Decision Support Tools (ERATMDST) program. The ERATMDST CHI specification is the FAA's vehicle to ensure an operationally suitable user interface is provided for the DSTs (such as...
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The design and evaluation of the Lightning Imaging Sensor Data Applications Display (LISDAD)
September 14, 1998
Conference Paper
Published in:
19th Conf. on Severe Local Storms, 14-18 September 1998, pp. 631-634.
Summary
The ultimate goal of the LISDAD system is to quantify the utility of total lightning infomation in short-term, severe-weather-forecasting operations. Secondary goals were to collect times series of various storm-cell parameters that relate to storm development and electrification and subsequently make these data available for post-facto analysis. To these ends scientists from NASA, NWS, and MIT/LL organized an effort to study the relationship of lightning and severe-weather on a storm-by-storm, and even cell-by-cell basis for as many storms as possible near Melbourne, Florida. Melbourne was chosen as it offers a unique combination of high probability of severe weather and proximity to major relevant sensors, specifically: NASA's total lightning mapping system at Kennedy Space Center (the LDAR system) at KSC [Lennon and Maier, 1991], a NWS / NEXRAD radar at Melbourne, and a prototype Integrated Terminal Weather System (ITWS), at Orlando. The ITWS system obtains cloud-to-ground lightning information from the National Lightning Detection Network (NLDN) via a link to Lexington, MA, and also uses NSSL's Severe Storms Analysis Package (NSSL / SSAP) to obtain information about various storm-cell parameters
Summary
The ultimate goal of the LISDAD system is to quantify the utility of total lightning infomation in short-term, severe-weather-forecasting operations. Secondary goals were to collect times series of various storm-cell parameters that relate to storm development and electrification and subsequently make these data available for post-facto analysis. To these ends...
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Comparisons between total lightning data, mesocyclone strength, and storm damage associated with the Florida tornado outbreak of February 23 1998
September 14, 1998
Conference Paper
Published in:
19th Conf. on Severe Local Storms, 14-18 September 1998, pp. 681-684.
Summary
During the late evening and early morning hours of February 22/23 1998, the worst tornado outbreak in recorded history occurred over the peninsula of central Florida. Analysis of KMLB Doppler radar data indicated at least 9 supercells developed over the region, with 4 of the supercells producing tornadoes. These 4 tornadic supercells produced a total of 7 tornadoes, some of them on the ground for tens of miles (Fig. 1.). A total of 42 fatalities were reported with over 260 injured. Monetary losses totaled over 100 million dollars. During this severe weather outbreak, National Weather Service Melbourne, in collaboration with the National Aeronautics and Space Administration and the Massachusetts Institute of Technology, was collecting data from a unique lightning observing system called Lightning Imaging Sensor Data Applications Display (LISDAD). This system has the capability to combine radar reflectivity data collected from the KMLB WSR-88D, cloud to ground data collected from the National Lightning Detection Network, and total lightning data collected from NASA's Lightning Detection And Ranging (LDAR) system. The object of this study is to compare total lightning data collected from the LISDAD system to mesocyclone strength as observed from the KMLB WSR-88D. These data will then be compared to the times of tornadic winds.
Summary
During the late evening and early morning hours of February 22/23 1998, the worst tornado outbreak in recorded history occurred over the peninsula of central Florida. Analysis of KMLB Doppler radar data indicated at least 9 supercells developed over the region, with 4 of the supercells producing tornadoes. These 4...
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Total lightning and radar storm characteristics associated with severe storms in Central Florida
September 14, 1998
Conference Paper
Published in:
19th Conf. on Severe Local Storms, 14-18 September 1998, pp. 639-642.
Summary
A number of prior studies have examined the association of lightning activity with the occurrence of severe weather and tornadoes, in particular. High flash rates are often observed in tornadic storms but not always. Taylor found that 23% of nontornadic storms and I% of non-severe storms had sferics rates comparable to the tornadic storms. MacGorman (1993) found that storms with mesocyclones produced more frequent intracloud (lC) lightning than cloud-ta-ground (CG) lightning. MacGorman (1993) and others suggest that the lightning activity accompanying tornadic storms will be dominated by intracloud lightning- with an increase in intracloud and total flash rates as the updraft increases in depth, size, and velocity. In a recent study, Perez et aI. (1998) found that CG flash rates alone are too variable to be a useful predictor of (F4, F5) tornado formation. Studies of non-tornadic storms have also shown that total lightning flash rates track the updraft, with rates increasing as the updraft intensifies and decreasing rapidly with cessation of vertical growth or downburst onset (Goodman et aI., 1988; Williams et aI., 1989). Such relationships result from the development of mixed phase precipitation and increased hydrometeor collisions that lead to the efficient separation of charge. Correlations between updraft strength and other variables such as cloud-top height, cloud water mass, and hail size have also been observed. In this paper we examine the total lightning activity (with high time resolution), and the associated Doppler radar time history of weaker (FO, Fl) tornadic storms in Florida. Much of the prior work has focused on tornadic supercells in the Great Plains.
Summary
A number of prior studies have examined the association of lightning activity with the occurrence of severe weather and tornadoes, in particular. High flash rates are often observed in tornadic storms but not always. Taylor found that 23% of nontornadic storms and I% of non-severe storms had sferics rates comparable...
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Total lightning as a severe weather diagnostic in strongly baroclinic systems in Central Florida
September 14, 1998
Conference Paper
Published in:
19th Conf. on Severe Local Storms, 14-18 September 1998, pp. 643-647.
Summary
Severe weather is defined by specific thresholds in wind. hail size and vorticity. All of these phenomena have close physical connections with vertical drafts in deep convection, which are themselves not directly measured with scanning Doppler radars of the NEXRAD type. Cloud electrification and lightning are particularly sensitive to these drafts because they modulate the supply of supercooled water which is the growth agent for the ice particles (ice crystals, graupel and hail) believed essential for electrical charge separation. For these reasons, one can expect correlations at the outset between total lightning activity and the development of severe weather which may aid in the understanding and prediction of these extreme weather conditions. The exploration of these ideas has historically been impeded by lack of good quantitative observations. A recent review of results on severe storm electrification (Williams, 1998) indicates a general absence of cases for which total lightning activity is documented over the lifetime of a severe storm. The recent development of LISDAD (Lightning Imaging Sensor Data Application Display) (Boldi, et aI., 1998) has largely remedied this problem. This paper is concerned with the use of LISDAD to quantify the behavior of total lightning in all types of severe weather, with a focus on a pair of extraordinarily electrified supercells in the Florida dry season.
Summary
Severe weather is defined by specific thresholds in wind. hail size and vorticity. All of these phenomena have close physical connections with vertical drafts in deep convection, which are themselves not directly measured with scanning Doppler radars of the NEXRAD type. Cloud electrification and lightning are particularly sensitive to these...
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Observations of total lightning associated with severe convection during the wet season in Central Florida
September 14, 1998
Conference Paper
Published in:
19th Conf. on Severe Local Storms, 14-18 September 1998, 635-638.
Summary
This paper will discuss findings of a collaborative lightning research project between the Massachusetts Institute of Technology, the National Weather Service (NWS) office in Melbourne (MLB), Florida and the National Aeronautics and Space Administration. In August 1996, NWS MLB received a workstation which incorporates data from the KMLB WSR-88D, Cloud to Ground (CG) stroke data from the National Lightning Detection Network (NLDN), and 3D volumetric lightning data collected from the Kennedy Space Centers' Lightning Detection And Ranging (LDAR) system. The two primary objectives of this lightning workstation, called Lightning Imaging Sensor Data Applications Display (L1SDAD), are to: a.) Observe how total lightning relates to severe convective storm morphology over central Florida, and, b.) Compare ground based total lightning data (LDAR) to a satellite based lightning detection system. This presentation will focus on objective #1.
Summary
This paper will discuss findings of a collaborative lightning research project between the Massachusetts Institute of Technology, the National Weather Service (NWS) office in Melbourne (MLB), Florida and the National Aeronautics and Space Administration. In August 1996, NWS MLB received a workstation which incorporates data from the KMLB WSR-88D, Cloud...
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Aircraft Vortex Spacing System (AVOSS) initial 1997 system deployment at Dallas/Ft. Worth (DFW) Airport
July 8, 1998
Project Report
Published in:
MIT Lincoln Laboratory Report NASA-L-3
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Summary
The potential hazard of aircraft encounters with the wake turbulence of preceding aircraft requires the use of minimum separations on landing that are a significant constraint on airport arrival capacity during instrument flight rules (IF) conditions. The National Aeronautics and Space Administration (NASA) Langley Research Center has been researching the development of the Aircraft Vortex Spacing System (AVOSS) which would dynamically change aircraft arrival separations based on the forecasted weather conditions and vortex behavior. An experimental AVOSS test system has been constructed at DFW airport and includes a large set of meteorological instruments, wake vortex sensors from three organizations, and an aircraft data collection system. All of this data are relayed to a central processing center at DFW for processing by automated meteorological data fusion algorithms and by NASA vortex behavior predictions software. An initial deployment and test of the DFW system was conducted during a three-week period in September/October of 1997. This document describes the overall system, the Lincoln-deployed sensors, including the Continuous-Wave Coherent lidar, and the meteorological data collection and processing system. Algorithms that were used to process the data for scientific use are described, as well as the conditions of the data collection and the data formats, for potential users of this database.
Summary
The potential hazard of aircraft encounters with the wake turbulence of preceding aircraft requires the use of minimum separations on landing that are a significant constraint on airport arrival capacity during instrument flight rules (IF) conditions. The National Aeronautics and Space Administration (NASA) Langley Research Center has been researching the...
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Global validation of single-station Schumann resonance lightning location
May 1, 1998
Journal Article
Published in:
J. Atmos. Sol.-Terr. Phys., Vol. 60, No. 7-9., May-June 1998, pp. 701-712.
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Summary
Global measurements of large, optically bright lightning events from the Optical Transient Detector (OTD) satellite are used to validate estimates of lightning location from single-station Schumann resonance (SR) data. Bearing estimates are obtained through conventional magnetic direction-finding techniques, while source range is estimated from the range-dependent impedance spectrum of an individual SR transients. An analysis of 40 such transients suggests that single-station techniques can locate lightning globally with an accuracy of 1-2 Mm. This is confirmed by further validation at close ranges from flashes detected by the National Lightning Detection Network (NLDN). Observations with both OTD and SR systems may be useful for globally locating lightning with necessary, if not sufficient, characteristics to trigger mesospheric sprites.
Summary
Global measurements of large, optically bright lightning events from the Optical Transient Detector (OTD) satellite are used to validate estimates of lightning location from single-station Schumann resonance (SR) data. Bearing estimates are obtained through conventional magnetic direction-finding techniques, while source range is estimated from the range-dependent impedance spectrum of an...
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