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| Titel |
Lightning characteristics observed by a VLF/LF lightning detection network (LINET) in Brazil, Australia, Africa and Germany |
| VerfasserIn |
H. Höller, H.-D. Betz, K. Schmidt, R. V. Calheiros, P. May, E. Houngninou, G. Scialom |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 20 ; Nr. 9, no. 20 (2009-10-20), S.7795-7824 |
| Datensatznummer |
250007692
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| Publikation (Nr.) |
 copernicus.org/acp-9-7795-2009.pdf |
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| Zusammenfassung |
This paper describes lightning characteristics as obtained in four sets of
lightning measurements during recent field campaigns in different parts of
the world from mid-latitudes to the tropics by the novel VLF/LF (very low
frequency/low frequency) lightning detection network (LINET). The paper
gives a general overview on the approach, and a synopsis of the statistical
results for the observation periods as a whole and for one special day in
each region. The focus is on the characteristics of lightning which can
specifically be observed by this system like intra-cloud and cloud-to-ground
stroke statistics, vertical distributions of intra-cloud strokes or peak
current distributions. Some conclusions regarding lightning produced
NOx are also presented as this was one of the aims of the tropical
field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides
Experiment) and TroCCiBras (Tropical Convection and Cirrus Experiment
Brazil) in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links
with Emphasis on the Upper Troposphere and Lower Stratosphere) and TWP-ICE
(Tropical Warm Pool-International Cloud Experiment) during November/December 2005
and January/February 2006, respectively, in the Darwin area in N-Australia, and of
AMMA (African Monsoon Multidisciplinary Analyses) in W-Africa during
June–November 2006.
Regional and temporal characteristics of lightning are found to be dependent
on orographic effects (e.g. S-Germany, Brazil, Benin), land-sea breeze
circulations (N-Australia) and especially the evolution of the monsoons
(Benin, N-Australia). Large intra-seasonal variability in lightning
occurrence was found for the Australian monsoon between the strong
convection during build-up and break phases and the weak active monsoon
phase with only minor lightning activity. Total daily lightning stroke rates
can be of comparable intensity in all regions with the heaviest events found
in Germany and N-Australia. The frequency of occurrence of such days was by
far the largest in N-Australia. In accordance with radar observed storm
structures, the intra-cloud stroke mean emission heights were found
distinctly different in Germany (8 km) as compared to the tropics (up to
12 km in N-Australia). The fraction of intra-cloud strokes (compared to all
strokes) was found to be relatively high in Brazil and Australia (0.83 and
0.82, respectively) as compared to Benin and Germany (0.64 and 0.69,
respectively).
Using stroke peak currents and vertical location information, lightning
NOx (LNOx) production under defined standard conditions can be compared
for the different areas of observation. LNOx production per standard stroke
was found to be most efficient for the N-Australian and S-German
thunderstorms whereas the yield from Brazilian and W-African strokes was
nearly 40% less. On the other hand, the main NO contribution in Brazil
was from intra-cloud (IC) strokes whereas in Benin it was due to
cloud-to-ground (CG) components. For the German and Australian strokes both
stroke types contributed similar amounts to the total NO outcome. |
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