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Some Properties of Lightning Flashes to a Tall Tower on a Mountain Top
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , x, 52 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:001
Keyword [en]
tall tower, mountain top, effective height, field enhancements, upward lightning initiation, upward positive lightning, upward bipolar lightning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:kth:diva-59215ISBN: 978-91-7501-208-7 (print)OAI: oai:DiVA.org:kth-59215DiVA: diva2:475394
Presentation
2012-01-18, Sal Q2, Osquldas väg 10, NB, Stockholm, 10:30 (English)
Opponent
Supervisors
Note
QC 20120119Available from: 2012-01-19 Created: 2012-01-10 Last updated: 2012-01-19Bibliographically approved
List of papers
1. On estimation of the effective height of towers on mountaintops in lightning incidence studies
Open this publication in new window or tab >>On estimation of the effective height of towers on mountaintops in lightning incidence studies
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2010 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 68, no 5, 415-418 p.Article in journal (Refereed) Published
Abstract [en]

Towers on mountaintops have more incidence of lightning than towers on the flat ground. Therefore towers on mountaintops are ascribed an effective height that is often considerably larger than the physical height of the tower. In this paper, we review and evaluate the definitions and methods that could be used to estimate the effective height of a given tower on mountaintop and propose a new definition based on an engineering model of lightning attachment. The results can be useful in designing lightning protection of communication/transmission lines and masts on mountaintops.

Keyword
Effective height, Lightning incidence, Towers
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-27073 (URN)10.1016/j.elstat.2010.05.014 (DOI)000283971700002 ()2-s2.0-77957142039 (Scopus ID)
Note
QC 20101210Available from: 2010-12-10 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
2. Measured current and close electric field changes associated with the initiation of upward lightning from a tall tower
Open this publication in new window or tab >>Measured current and close electric field changes associated with the initiation of upward lightning from a tall tower
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2012 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, D08102- p.Article in journal (Refereed) Published
Abstract [en]

We examine in detail the simultaneous lightning current waveforms, close electric field changes, and lightning location system data for upward lightning discharges initiated from the Gaisberg Tower (GBT) from 2005 to 2009. Out of 205 upward flashes, most of them (87% or 179/205) were initiated from the tower top without any nearby preceding lightning activity (called "self-initiated"), whereas 26 upward flashes (13%) were initiated from the tower top with immediately preceding nearby lightning activity (called "nearby-lightning-triggered"), including 15 positive ground flashes, one negative ground flashes, and 10 cloud discharges. The possible reasons for self-initiated upward flashes dominating at the GBT could be the field enhancement due to the Gaisberg Mountain above the surrounding terrain and low altitude of charge region during non-convective season (September to March), since we note that self-initiated lightning at the GBT occurred predominantly (79% or 142/179) during non-convective season. On the other hand the majority (85% or 22/26) of nearby-lightning-triggered upward flashes at the GBT occurring during convective season (April to August) and 80 nearby-lightning-triggered upward flashes out of 81 upward flashes observed at the ten tall towers in Rapid City in South Dakota of USA occurring during summer seasons, could be due to the result of high altitude of charge region. The triggering flashes were detected to be within 1 and 18 km distance and the time intervals between them and upward lightning initiation are in the range of 0.3 to 90.7 ms.

Keyword
Charge regions, Cloud discharge, Electric field change, Field enhancement, Ground flash, High altitude, Lightning activity, Lightning currents, Lightning location systems, Low altitudes, Measured currents, South dakotas, Summer season, Time interval, Upward lightning
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:kth:diva-59213 (URN)10.1029/2011JD017269 (DOI)000303122600005 ()2-s2.0-84859909925 (Scopus ID)
Funder
StandUp
Note

QC 20120522. Updated from submitted to published.

Available from: 2012-01-10 Created: 2012-01-10 Last updated: 2017-12-08Bibliographically approved
3. Characteristics of upward positive lightning flashes initiated from the Gaisberg Tower
Open this publication in new window or tab >>Characteristics of upward positive lightning flashes initiated from the Gaisberg Tower
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2012 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, no 6, D06110- p.Article in journal (Refereed) Published
Abstract [en]

We report the measured current characteristics of positive lightning discharges to the Gaisberg Tower (GBT) in Austria from 2000 to 2009. On the basis of the recorded current waveforms, a total of 26 flashes consisting of initial stage only were identified as upward positive discharges initiated by an upward negative leader from GBT. They accounted for 4% (26/652) of the total flashes recorded at the GBT. Nineteen (73%) out of the 26 positive flashes occurred during nonconvective season (September-March). Median values of flash peak current, flash duration, charge transfer, and action integral were determined as 5.2 kA, 82 ms, 58 C, and 0.16 x 10(3) A(2) s, respectively. Current pulses of high repetition rate superimposed on the initial portion of initial continuous current are inferred to be associated with the upward negative stepped leader process. The weighted arithmetic means of leader pulse peak current, leader pulse duration, leader interpulse interval, and leader pulse charge are 3 kA, 31 mu s, 32 mu s, and 42 mC, respectively. On the basis of an assumed stepped leader speed in the range of 8 x 10(4) to 4.5 x 10(5) m/s an upward negative stepped leader channel charge density of 15-87 mC/m, a leader length of 168-945 m, and an average leader step length of 2.4-13.3 m were estimated. The upward negative stepped leader channel charge density and length are significantly larger and smaller than their counterparts in downward negative stepped leaders, respectively, while the upward leader step length is consistent with previous studies. Possible reasons for this are discussed.

National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:kth:diva-59211 (URN)10.1029/2011JD016903 (DOI)000302236900004 ()2-s2.0-84859451112 (Scopus ID)
Funder
StandUp
Note

QC 20120507. Updated from submitted to published.

Available from: 2012-01-10 Created: 2012-01-10 Last updated: 2017-12-08Bibliographically approved
4. Characteristics of upward bipolar lightning flashes observed at the Gaisberg Tower
Open this publication in new window or tab >>Characteristics of upward bipolar lightning flashes observed at the Gaisberg Tower
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2011 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, D13106- p.Article in journal (Refereed) Published
Abstract [en]

We analyze current records for 21 upward initiated bipolar lightning flashes observed at the Gaisberg Tower (GBT) in Austria from 2000 to 2009. A bipolar lightning flash occurrence of 3% (21/652) is found during the 10-year observation period. Thirteen (62% or 13/21) of them occurred in nonconvective season (September-March). On the basis of the classification suggested by Rakov and Uman (2003), 13 (62%) of the 21 bipolar flashes belong to Type 1 associated with a polarity reversal during the initial stage (IS) current, five belong to Type 2 associated with different polarities of the IS current and the following return strokes, one belongs to Type 3 associated with return strokes of opposite polarity following the IS, and two of them are not assigned. We also find that the initial polarity reversal from negative to positive occurs more often (76% or 16/21) than that from positive to negative within a bipolar flash, in agreement with observations in other studies. The geometric mean (GM) and arithmetic mean (AM) of the total absolute charge transfer are 99.5 C and 125 C, with the GM and AM total flash duration of 320 ms and 396 ms, respectively. From simultaneous current and high-speed video measurements of one bipolar flash, within the field of view, the positive charge was transferred along one branch initially, followed by the negative charge transfer after cessation of the luminosity for 142 ms, while the other two branches connected to the main channel always contributed to the negative charge transfer during the whole process.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-37158 (URN)10.1029/2011JD015634 (DOI)000292609200002 ()2-s2.0-79960249760 (Scopus ID)
Available from: 2011-08-03 Created: 2011-08-02 Last updated: 2017-12-08Bibliographically approved

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