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Positive charge in the stratiform cloud of a mesoscale convective system

January 16, 2001
  |
Journal Article
Author:
Thomas C. Marshall
…
Published in:
J. Geophys. Res., Vol. 106, No. D1, 16 January 2001, pp. 1157-1163.
Topic:
weather
R&D area:
R&D group:

Summary

A balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in-cloud positive charge regions. These charge regions are located at altitudes of 5.1-5.6 km and 6.4-6.8 km, above the level of 0 degree C at 4.2 km. The two positive charge regions are the likely sources of six positive cloud-to-ground flashes with large peak currents (>32 kA) that occurred within 60 km of the balloon during its flight. The amount of charge transferred by three of these positive flashes that made Q bursts is calculated in the range of 97-196 C. Flashes of this sort are known to produce sprites and elves in the mesosphere. The positive charge regions in this stratiform cloud are substantially lower than the 10-km altitude commonly assumed for the positive charge in many sprite modeling studies.
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Summary

A balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in-cloud positive charge regions. These charge regions are located at altitudes of 5.1-5.6 km and 6.4-6.8 km, above the level of 0 degree C at 4.2 km. The...

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Positive charge in the stratiform cloud of a mesoscale convective system

Sprites, elves, and glow discharge tubes

January 1, 2001
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Journal Article
Author:
Earle R. Williams
Published in:
Phys. Today, Vol. 54, No. 11, November 2001, pp. 41-47.
Topic:
weather
R&D area:
R&D group:

Summary

In the 1920's, the Scottish physicist C.T.R. Wilson predicted the existence of brief flashes of light above large thunderstorms. Almost 70 years later, Bernard Vonnegut of SUNY Albany realized that evidence for Wilson's then-unconfirmed predictions might appear in video imagery of Earth's upper atmosphere recorded by space-shuttle astronauts. He encouraged NASA's William Boeck and Otha Vaughan to look for evidence. Their search was successful. At the 1990 fall meeting of the American Geophysical Union, Boeck and Vaughan presented evidence for upper-atmosphere flashes. Evidence of a different nature came from the University of Minnesota's John Winckler and his colleagues, who had serendipitously observed a flash in moonless night-time skies over Minnesota in 1989. These early findings inspired two independent field programs to target the new phenomenon. In the summer of 1993, Walter Lyons of FMA Research set up detectors on Yucca Ridge in the foothills of the Rocky Mountains. That same summer, Davis Sentman of the University of Alaska Fairbanks (UAF) sought to record the flashes from an aircraft flying over the Great Plains. Within a day of each other, the two research teams had documented what turned out to be a common phenomenon in the mesosphere. In doing so, they initiated not only a new kind of continental-scale field experiment but also—and more important—a new interdisciplinary area of research.
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Summary

In the 1920's, the Scottish physicist C.T.R. Wilson predicted the existence of brief flashes of light above large thunderstorms. Almost 70 years later, Bernard Vonnegut of SUNY Albany realized that evidence for Wilson's then-unconfirmed predictions might appear in video imagery of Earth's upper atmosphere recorded by space-shuttle astronauts. He encouraged...

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Sprites, elves, and glow discharge tubes

A statistical analysis of approach winds at capacity-restricted airports

November 30, 2000
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Project Report
Author:
Glenn H. Perras
…
Published in:
MIT Lincoln Laboratory Report ATC-296
Topic:
weather
R&D area:
R&D group:

Summary

A study was conducted on six major U.S. airports with closely-spaced parallel (CSP) runways that become capacity-restricted during times of lowered cloud ceilings and visibilities. These airports were SFO, BOS, EWR, PHL, SEA, and STL. Efforts are underway to develop a feasible system for simultaneous CSP approaches, which would increase the capacity at these airports during restrictive weather conditions. When considering any new procedure, the wind conditions on approach are needed to understand the impact of wake turbulence transport. Wind observations from aircraft that are equipped with Meteorological Data Collection and Reporting System (MDCRS) capabilities were used to conduct a statistical analysis on wind characteristics at each airport. Data from January 1997 through December 1999 were used in each analysis. Data analysis techniques and the statistical results are presented in this report. This information is expected to support procedure and benefits assessment models.
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Summary

A study was conducted on six major U.S. airports with closely-spaced parallel (CSP) runways that become capacity-restricted during times of lowered cloud ceilings and visibilities. These airports were SFO, BOS, EWR, PHL, SEA, and STL. Efforts are underway to develop a feasible system for simultaneous CSP approaches, which would increase...

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A statistical analysis of approach winds at capacity-restricted airports

WSP utility libraries

October 23, 2000
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Project Report
Author:
Oliver J. Newell
Published in:
MIT Lincoln Laboratory Report ATC-284
Topic:
weather
R&D area:
R&D group:

Summary

The ASR-9 Weather Systems Processor (WSP) augments the weather detection capability of existing ASR-9 radars to include low-level wind shear warnings, storm cell tracking and prediction, and improved immunity to false weather echoes due to anomalous propagation (AP). To economically develop and field an operational system at the 34 WSP sites, the FAA is pursuing a strategy that leverages the software written during the 10-year R&D phase of the project. To that end, the software developed at Lincoln Laboratory has been "hardened" to ensure reliable, continuous operation, and has been ported to a "Phase II" prototype built around the latest generation of COTS hardware. A significant number of the hardened software modules are being used in the production version of the WSP with only minor modifications. Included as part of the software are a number of lower-level utility libraries to provide basic services such as memory management and network communication. This document provides a detailed description of these common utility libraries.
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Summary

The ASR-9 Weather Systems Processor (WSP) augments the weather detection capability of existing ASR-9 radars to include low-level wind shear warnings, storm cell tracking and prediction, and improved immunity to false weather echoes due to anomalous propagation (AP). To economically develop and field an operational system at the 34 WSP...

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WSP utility libraries

Weather sensing and data fusion to improve safety and reduce delays at major west coast airports

November 30, 1999
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Project Report
Author:
James E. Evans
…
Published in:
MIT Lincoln Laboratory Report ATC-290
Topic:
air traffic control
R&D area:
R&D group:

Summary

The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive an Integrated Terminal Weather System (ITWS). This report considers the Los Angeles (LAX), San Francisco (SFO), Seattle (SEA) and Portland, OR (PDX) international airports. A number of visits were made to the various ATC facilities to better understand their weather decision support operational needs. Analyses were made of an incident of lightning strikes to two aircraft at SEA in February 1999, and a prototype terminal winds product was developed for LAX that uses profilers as well as plane reports to update the the National Weather Service (NWS) Rapid Update Cycle (RUC) winds estimates. We found that an augmented ITWS could potentially address safety concerns for triggered lightning strikes and vertical wind shear in winter storms at Portland and Seattle. An augmented ITWS terminal winds product (that uses wind profiler data in addition to the current ITWS sensors) could provide very large delay reductions for LAX and SFO during winter storms as a component of a wake vortex advisory system. This augmented product also could provide significant delay reduction benefits at SEA. The sensors required to obtain the projected benefits at SFO do not exist currently. Portland may warrant additional sensors to address the vertical wind shear problems, and LAX would require additional sensors for a wake vortex advisory system. We recommend near-term experimental measurements at PDX to determine the optimum sensor mix and that an operational evaluation of the prototype augmented ITWS terminal winds product be carried out at LAX to determine if the current sensor mix can meet operational needs. Lightning strike data at SEA and PDX should be analyzed to determine if a proposed triggered lightning predictant is accurate.
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Summary

The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive an Integrated Terminal Weather System (ITWS). This report considers the Los Angeles (LAX), San Francisco...

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Weather sensing and data fusion to improve safety and reduce delays at major west coast airports

Criteria for sprites and elves based on Schumann resonance observations

July 27, 1999
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Journal Article
Author:
Everest W. Huang
…
Published in:
J. Geophys. Res., Vol. 104, No. D14, 27 July 1999, pp. 16,943-16,964.
Topic:
weather
R&D area:
R&D group:

Summary

Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the measured time constants for lightning charge transfer with the electrostatic relaxation time at altitudes of nighttime sprite initiation (50-70 km) generally validate the electrostatic assumption in predictions made initially by Wilson [1925]. The measured charge moments (Q dS = 200-2000 C-km) are large in comparison with ordinary negative lightning but are generally insufficient to account for conventional air breakdown at sprite altitudes. The measured charge moments, however, are sufficient to account for electron runaway breakdown, and the long avalanche length in this mechanism also accounts for the exclusive association of sprites with ground flashes of positive polarity. The association of elves with large peak currents (50-200 kA) measured by the National Lightning Detection Network in a band pass beyond the Schumann resonance range is consistent with an electromagnetic pulse mechanism for these events.
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Summary

Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the...

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Criteria for sprites and elves based on Schumann resonance observations

The behavior of total lightning activity in severe Florida thunderstorms

July 1, 1999
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Journal Article
Author:
Earle R. Williams
…
Published in:
Atmos. Res., Vol. 51, Nos. 3-4, July 1999, pp. 245-265.
Topic:
weather
R&D area:
R&D group:

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.
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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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The behavior of total lightning activity in severe Florida thunderstorms

Schumann Resonances and the temporal-spatial dynamics of global thunderstorm activity

June 7, 1999
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Conference Paper
Author:
V. Mushtak
…
Published in:
11th Int. Conf. on Atmospheric Electricity, 7-11 June 1999, pp. 698-700.
Topic:
weather
R&D area:
R&D group:

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.
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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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Schumann Resonances and the temporal-spatial dynamics of global thunderstorm activity

The relationship between the background and transient signals in Schumann resonances

June 7, 1999
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Conference Paper
Author:
Earle R. Williams
…
Published in:
Proc. 11th Int. Conf. on Atmospheric Electricity, 7-11 June 1999, pp. 758-761.
Topic:
weather
R&D area:
R&D group:

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.
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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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The relationship between the background and transient signals in Schumann resonances

Total lightning activity associated with tornadic storms

June 7, 1999
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Conference Paper
Author:
Steven J. Goodman
…
Published in:
11th Int. Conf. on Atmos. Electr., 7-11 June 1999, pp. 515-518.
Topic:
weather
R&D area:
R&D group:

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.
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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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Total lightning activity associated with tornadic storms
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