The Evolution of Total Lightning and Radar Reflectivity Characteristics of Two Mesoscale Convective Systems Over Houston, Texas

The Evolution of Total Lightning and Radar Reflectivity Characteristics of Two Mesoscale Convective Systems Over Houston, Texas
Author: Charles Lee Hodapp
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:

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Two mesoscale convective systems (MCSs) passed over the Houston Lightning Detection and Ranging (LDAR) network on 31 October 2005 and 21 April 2006. As the MCSs traverse the LDAR network, the systems slowly mature with a weakening convective line and a developing stratiform region and radar bright band. The intensification of stratiform region precipitation, including the bright band, is thought to play an important role in stratiform lightning structure, charge structure, and total lightning production of MCSs. The stratiform areas quadruple in size and the mean reflectivity values increase substantially by ~ 6 dB. As the stratiform region matures, VHF source density plots show a lightning pathway that slopes rearward and downward from the back of the convective line and into the stratiform region. At early times for both MCSs, the pathway extends horizontally rearward 40 to 50 km into the stratiform region at an altitude of 9 to 12 km. Near the end of the analysis time period, the pathway slopes rearward 40 km and downward through the transition zone before extending 40 to 50 km in the stratiform region at an altitude of 4 - 7 km. The sloping pathway likely results from charged ice particles advected from the convective line by storm relative front-to-rear flow while the level pathway extending further into the stratiform region is likely caused by both charge advection and local in-situ charging. As the stratiform region matures, the stratiform flash rates double and lightning heights decrease. The percentage of lightning flashes originating in the stratiform region increases significantly from 10 - 20% to 50 - 60%. Overall, the number of positive cloud-to-ground flashes in the stratiform region also increases. Between both MCSs, 60% of the positive CGs originated in the convective or transition regions. Both in-situ charging mechanisms created by the development of the mesoscale updraft and charge advection by the front-to-rear flow likely contribute to the increased electrification and lightning in the stratiform region.

Three-Dimensional Radar and Total Lightning Characteristics of Mesoscale Convective Systems

Three-Dimensional Radar and Total Lightning Characteristics of Mesoscale Convective Systems
Author:
Publisher:
Total Pages:
Release: 2003
Genre:
ISBN:

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The radar and electrical characteristics of three linear leading convective/trailing stratiform midlatitude mesoscale convective systems (MCSs) that passed through Dallas-Fort Worth, Texas on the following dates are examined: 1) 7-8 April 2002, 2) 12-13 October 2001, and 3) 16 June 2002. Quantitative results from the April and June MCSs are presented, but data problems with the October MCS restricted partitioned analysis to qualitative results. The convective line produced ~69% and ~93% of the total cloud-to-ground (CG) lightning flashes in the April and June MCSs, respectively. The convective line CG flash rate averaged 12.3 flashes min-1 (53.6 flashes min-1) in the April (June) case study, and only 7.5% (2%) of these flashes were positive in polarity. Lightning Detection and Ranging (LDAR II) source data identified two main electrically-active regions present within the convective line in the following temperature layers: 1) 0 to -25 & deg;C, and 2) -35 to -55 & deg;C. The lower region (1) was most likely a combination of the main negative and the lower positive charge centers of the thunderstorm tripole, and the upper region (2) was most likely the upper positive charge center of this tripole. Convective echo volume aloft (e"30 dBZ, 0 to -40 & deg;C) was strongly correlated to convective lightning activity, suggesting that the presence of strong updrafts and differential sedimentation caused convective line electrification via the non-inductive charging (NIC) mechanism. The stratiform region CG flash rate averaged 2.2 flashes min-1 (4.5 flashes min-1) in the April (June) case study, and ~45% (~27%) of these flashes were positive in polarity. LDAR II source data identified one primary electrically-active layer (at -10 to -25 & deg;C) that was sloped from the upper portions of the convective line rearward to just above the bright band in the stratiform region. A small and spatially distinct secondary electrically-active layer (at ~ -40 & deg;C) was located towards.

Lightning: Principles, Instruments and Applications

Lightning: Principles, Instruments and Applications
Author: Hans Dieter Betz
Publisher: Springer Science & Business Media
Total Pages: 641
Release: 2008-12-04
Genre: Science
ISBN: 140209079X

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Lightning represents a natural phenomenon of substantial interest. Due to its complex nature, research continues in many countries and reveals amazing results. Lightning is actively observed because of its relevance to Earth climate and air composition in addition to the classical aspects of related human fatalities and damage to forests, buildings, power lines, aircraft, structures and electronic devices. In this volume, the most important contemporary questions on lightning are addressed and analyzed under many experimental and theoretical aspects. Lightning detection techniques using ground-based and space-borne methods are described, along with network engineering and statistical analysis. Contributions detail research on atmospheric electricity, cloud physics, lightning physics, modeling of electrical storms and middle atmospheric events. Special phenomena such as triggered lightning and sprite observations are examined. Lightning-induced nitrogen oxides and their effects on atmospheric chemistry and climate are discussed. Each topic is presented by international experts in the field. Topics include: * air chemistry * convective storms * infrasound from lightning * lightning and climate change * lightning and precipitation * lightning and radiation * lightning and supercells * lightning and thunderstorms * lightning detection * lightning from space * lighting protection * lightning return strokes * observations and interpretations * spatial distribution and frequency * triggered lightning * weather extremes

Total Lightning Characteristics of Ordinary Convection

Total Lightning Characteristics of Ordinary Convection
Author: Shane Michael Motley
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:

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Twenty-two isolated, non-severe, warm season thunderstorms (ordinary thunderstorms) were examined to test possible correlations between three-dimensional lightning flash characteristics and the complex evolution of the microphysical and kinematic processes involved in the electrical development of thunderstorms. Nine of the thunderstorm cases examined occurred within range of Vaisala Inc.'s Dallas-Fort Worth (DFW) Lightning Detection and Ranging (LDAR) network and the other thirteen cases occurred within range of the Texas A & M University Houston LDAR Network. Cloud-toground (CG) flash data were obtained from the National Lightning Detection Network (NLDN). The kinematic and microphysical properties of each convective cell were inferred from level II Weather Surveillance Radar 1988-Doppler data. Lightning properties were compared to radar reflectivity, Vertically Integrated Liquid, Severe Hail Index, and Vertically Integrated Ice (VII) (i.e. the measure of the precipitation ice water content in and above the mixed phase ( -40°C