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  • 1
    Publication Date: 2019-07-19
    Description: The electrification (or lack thereof) of pyrocumulus clouds is examined for several different wildfires that occurred during 20122013. For example, pyrocumulus clouds above three Colorado wildfires (Hewlett Gulch, High Park, and Waldo Canyon; all occurred during summer 2012) electrified and produced small intracloud discharges whenever the smoke plumes grew to high altitudes (over 10 km above mean sea level, or MSL). This occurred during periods of rapid wildfire growth, as indicated by the shortwave infrared channel on a geostationary satellite, as well as by incident reports. In the Hewlett Gulch case, the fire growth led to increased updrafts within the plume, as inferred by multipleDoppler radar syntheses, which led to the vertical development and subsequent electrification a life cycle as short as 30 minutes. The lightning, detected by a threedimensional lightning mapping network, was favored in highaltitude regions (~10 km MSL) containing modest reflectivities (25 dBZ and lower), ~0 dB differential reflectivity, and reduced correlation coefficient (~0.60.7). This indicated the likely presence of ice particles (crystals and aggregates, possibly rimed) mixed with ash. Though neither multipleDoppler nor polarimetric observations were available during the electrification of the High Park and Waldo Canyon plumes, their NEXRAD observations showed reflectivity structures consistent with Hewlett Gulch. In addition, polarimetric and multipleDoppler scanning of unelectrified High Park plumes indicated only irregularly shaped ash, and not ice, was present (i.e., reflectivities 〈 25 dBZ, differential reflectivity 〉 5 dB, correlation 〈 0.4), and there was no broaching of the 10 km altitude. Based on these results, the electrification likely was caused by icebased processes that did not involve significant amounts of graupel. Results for pyrocumulus clouds above notable 2013 wildfires that also experienced rapid growth (e.g., Black Forest, Yarnell Hill, West Fork, Tres Lagunas, etc.) will be compared against the 2012 cases, with special emphasis on polarimetric NEXRAD and available lightning measurements, in order to better understand the physical processes responsible for pyrocumulus electrification.
    Keywords: Meteorology and Climatology
    Type: M13-2836 , 2013 American Geophysical Union (AGU) Fall Meeting; Dec 09, 2013 - Dec 13, 2013; San Francisco, CA; United States
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  • 2
    Publication Date: 2019-07-19
    Description: Sprites are caused by luminous electrical breakdown of the upper atmosphere, and frequently occur over large mesoscale precipitation systems. Two spriteproducing storms (on 8 and 25 June) were observed in Colorado during the summer of 2012. Unlike most past studies of sprites, these storms were observed by a polarimetric radar the CSUCHILL facility which provided both PPI and RHI scans of the cases. Also available were multipleDoppler syntheses from CSUCHILL, local NEXRAD radars, and the CSUPawnee radar; as well as data from the Colorado Lightning Mapping Array (COLMA), high speed cameras, and other lightningdetection instrumentation. This unique dataset provided an unprecedented look at the detailed kinematic and microphysical structures of the thunderstorms as they produced sprites, including electrical alignment signatures in the immediate location of the charge layers neutralized by spriteparent positive cloudtoground lightning strokes. One of the spriteproducing cases (25 June) featured an anomalous charge structure and may serve as a model for how sprites can be produced over convection rather than the more typical stratiform regions. Also to be presented will be evidence for advection of charge into a common stratiform precipitation region (on 8 June), which was then tapped by lightning originating from multiple different convective cores to produce sprites. Depending on the outcome of the 2013 convective season, polarimetric data from additional storms that produce sprites and other transient luminous events (TLEs) may be presented.
    Keywords: Meteorology and Climatology
    Type: M13-2684 , American Meteorological Society (AMS) Conference on Radar Meterology; Sep 16, 2013 - Sep 20, 2013; Breckenridge, CO; United States
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  • 3
    Publication Date: 2019-07-19
    Description: During the spring and summer of 2006, a network of eight lightning mapping stations has been set up in the greater DC metropolitan area to monitor the total lightning activity in storms over Virginia, Maryland and the Washington DC area. The network is a joint project between New Mexico Tech, NASA, and NOAA/National Weather Service, with real-time data being provided to the NWS for use in their forecast and warning operations. The network utilizes newly available portable stations developed with support from the National Science Foundation. Cooperating institutions involved in hosting mapping stations are Howard University, Montgomery County Community College in Rockville MD, NOAA/NWS's Test and Evaluation Site in Sterling, VA, College of Southern Maryland near La Plata MD, the Applied Physics Laboratory of Johns Hopkins University, Northern Virginia Community College in Annandale, VA, the University of Maryland at Baltimore County, and George Mason University (Prince William Campus) in Manassas, VA. The network is experimental in that its stations a) operate in the upper rather than the lower VHF (TV channel 10, 192-198 MHz) to reduce the radio frequency background noise associated with urban environments, and b) are linked to the central processing site via the internet rather than by dedicated wireless communication links. The central processing is done in Huntsville, AL, and updated observations are sent to the National Weather Service every 2 min. The observational data will also be available on a public website. The higher operating frequency results in a decrease in signal strength estimated to be about 15-20 dB, relative to the LMA networks being operated in northern Alabama and central Oklahoma (which operate on TV channels 5 and 3, respectively). This is offset somewhat by decreased background noise levels at many stations. The receiver threshold levels range from about -95 dBm up to -80 dBm and the peak lightning signals typically extend 15-20 dB above the threshold values. Despite having decreased sensitivity, the network locates lightning in plan position over all of Maryland and Delaware, much of Virginia, and into Southern Pennsylvania and New Jersey. 3-D coverage is provided out to 100-150 km range from the Sterling WFO including the 3 major DC commercial airports (Reagan National, Dulles International, and Baltimore Washington International). The network will eventually consist of 10 or more stations, which will extend and improve its coverage.
    Keywords: Meteorology and Climatology
    Type: 2006 Fall American Geophysical Union Meeting; Dec 11, 2006 - Dec 15, 2006; San Francisco, CA; United States
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  • 4
    Publication Date: 2019-07-17
    Description: 3-dimensional lightning mapping observations obtained during the MEaPRS program in central Oklahoma during June, 1998 have been compared with observations of the discharges from space, obtained by NASA's Lightning Imaging Sensor (LIS) on the TRMM satellite. Excellent spatial and temporal correlations were observed between the two sets of observations. Most of the detected optical events were associated with intracloud discharges that developed into the upper part of the storm. Cloud-to-ground discharges that were confined to mid- and lower-altitudes tended not to be detected by LIS. Extensive illumination tended to occur in impulsive bursts toward the end or part way through intracloud flashes and appeared to be produced by energetic K-changes that typically occur at these times.
    Keywords: Meteorology and Climatology
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  • 5
    Publication Date: 2019-07-27
    Description: No abstract available
    Keywords: Earth Resources and Remote Sensing; Meteorology and Climatology
    Type: M13-3001 , American Meteorological Society (AMS) Conference on Radar Meteorology; 16-20 Sept. 2013; Breckenridge, CO; United States
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  • 6
    Publication Date: 2019-07-27
    Description: No abstract available
    Keywords: Meteorology and Climatology
    Type: M13-3002 , American Meteological Society (AMS) Conference on Radar Meteorology; 16-20 Sept. 2013; Brenkenridge, CO; United States
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  • 7
    Publication Date: 2019-07-19
    Description: Pyrocumulus clouds above three Colorado wildfires (Hewlett Gulch, High Park, and Waldo Canyon; all occurred during summer 2012) electrified and produced small intracloud discharges whenever the smoke plumes grew to high altitudes (over 10 km above mean sea level, or MSL). This occurred during periods of rapid wildfire growth, as indicated by the shortwave infrared channel on a geostationary satellite, as well as by incident reports. In the Hewlett Gulch case, the fire growth led to increased updrafts within the plume, as inferred by multiple Doppler radar syntheses, which led to the vertical development and subsequent electrification a life cycle as short as 30 minutes. The lightning, detected by a threedimensional lightning mapping network, was favored in highaltitude regions (~10 km MSL) containing modest reflectivities (25 dBZ and lower), ~0 dB differential reflectivity, and reduced correlation coefficient (~0.60.7). This indicated the likely presence of ice particles (crystals and aggregates, possibly rimed) mixed with ash. Though neither multipleDoppler nor polarimetric observations were available during the electrification of the High Park and Waldo Canyon plumes, their NEXRAD observations showed reflectivity structures consistent with Hewlett Gulch. In addition, polarimetric and multipleDoppler scanning of unelectrified High Park plumes indicated only irregularly shaped ash, and not ice, was present (i.e., reflectivities 〈 25 dBZ, differential reflectivity 〉 5 dB, correlation 〈 0.4), and there was no broaching of the 10 km altitude. Based on these results, the electrification likely was caused by icebased processes that did not involve significant amounts of graupel. The results demonstrate the scientific value of multipleDoppler and polarimetric radar observations of wildfire smoke plumes including the ability to distinguish between regions of pure hydrometeors, regions of pure ash, and mixtures of both and also suggest a possible new application for lightning data in monitoring wildfires.
    Keywords: Meteorology and Climatology
    Type: M13-2683 , American Meteorological Society (AMS) Conference on Radar Meteorology; Sep 16, 2013 - Sep 20, 2013; Breckenridge, CO; United States
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  • 8
    Publication Date: 2019-07-19
    Description: A seven station, short base-line Lightning Mapping Array was installed at the Camp Blanding International Center for Lightning Research and Testing (ICLRT) during April 2011. This network will support science investigations of Terrestrial Gamma-Ray Flashes (TGFs) and lightning initiation using rocket triggered lightning at the ICLRT. The network operations and data processing will be carried out through a close collaboration between several organizations, including the NASA Marshall Space Flight Center, University of Alabama in Huntsville, University of Florida, and New Mexico Tech. The deployment was sponsored by the Defense Advanced Research Projects Agency (DARPA). The network does not have real-time data dissemination. Description, status and plans will be discussed.
    Keywords: Meteorology and Climatology
    Type: M11-0554 , Sothern Thunder 2011 (ST11) Workshop; Jul 11, 2011 - Jul 14, 2011; Norman, OK; United States
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  • 9
    Publication Date: 2019-07-13
    Description: Two sprite-producing thunderstorms were observed on 8 and 25 June 2012 in northeastern Colorado by a combination of low-light cameras, a lightning mapping array, polarimetric and Doppler radars, the National Lightning Detection Network, and charge moment change measurements. The 8 June event evolved from a tornadic hailstorm to a larger multicellular system that produced 21 observed positive sprites in 2 h. The majority of sprites occurred during a lull in convective strength, as measured by total flash rate, flash energy, and radar echo volume. Mean flash area spiked multiple times during this period; however, total flash rates still exceeded 60 min(sup 1), and portions of the storm featured a complex anomalous charge structure, with midlevel positive charge near 20degC. The storm produced predominantly positive cloud-to-ground lightning. All sprite-parent flashes occurred on the northeastern flank of the storm, where strong westerly upper level flow was consistent with advection of charged precipitation away from convection, providing a pathway for stratiform lightning. The 25 June event was another multicellular hailstorm with an anomalous charge structure that produced 26 positive sprites in less than 1 h. The sprites again occurred during a convective lull, with relatively weaker reflectivity and lower total flash rate but relatively larger mean flash area. However, all sprite parents occurred in or near convection and tapped charge layers in adjacent anvil cloud. The results demonstrate the sprite production by convective ground strokes in anomalously charged storms and also indicate that sprite production and convective vigor are inversely related in mature storms.
    Keywords: Meteorology and Climatology
    Type: MSFC-E-DAA-TN35329 , Journal of Geophysical Research, Atmospheres (ISSN 2169-897X); 121; 16; 9675–9695
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  • 10
    Publication Date: 2019-07-17
    Description: 3-dimensional lightning mapping observations were obtained in central Oklahoma during June 1998, using New Mexico Tech's Lightning Mapping Array (LMA). The results have been compared with observations of the discharges from space obtained by NASA's Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) spacecraft. Excellent spatial and temporal correlations were obtained between the two sets of observations. All discharges seen by LIS were mapped by the LMA. Most of the detected optical events were associated with lightning channels that extended into the upper part of the storm. Cloud-to-ground discharges that were confined to mid- and lower-altitudes tended to be detected by LIS at the time of late-stage return strokes. Extensive illumination tended to occur in impulsive bursts toward the end or part way through intracloud discharges and appeared to be produced by energetic K-changes that typically occur at these times.
    Keywords: Meteorology and Climatology
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