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| Titel |
Lightning characteristics over the eastern coast of the Mediterranean during different synoptic systems |
| VerfasserIn |
Y. Ben Ami, O. Altaratz, Y. Yair, I. Koren |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Sciences ; 15, no. 11 ; Nr. 15, no. 11 (2015-11-04), S.2449-2459 |
| Datensatznummer |
250119770
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| Publikation (Nr.) |
 copernicus.org/nhess-15-2449-2015.pdf |
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| Zusammenfassung |
Thunderstorm activity takes place in the eastern Mediterranean mainly through
the boreal fall and winter seasons during synoptic systems of Red Sea Trough
(RST), Red Sea Trough that closed a low over the sea (RST-CL), and Cyprus
Low (during fall – FCL and winter – WCL). In this work we used the Israeli
Lightning Location System ground strokes data set, between October 2004 and
December 2010, for studying the properties of lightning strokes and their link
to the thermodynamic conditions in each synoptic system.
It is shown that lightning activity dominates over sea during WCL and
FCL systems (with maximum values of 1.5 in WCL, and
2.2 km−2 day−1 in FCL) and have a dominant component over land during the RST
and RST-CL days. The stronger instability (high Convective Available Potential
Energy (CAPE) values of 762 ± 457 J kg−1)
during RST-CL days together with the higher altitude of the
clouds' mixed-phase region (3.6 ± 0.3 km), result in a slightly higher
density of ground strokes during this system but a lower fraction of positive
ground strokes (3 ± 0.5 %). In general the fraction of positive
strokes was found to be inversely correlated with the sea surface
temperature: it increases from 1.2 % in early fall to 17.7 % in late
winter, during FCL and WCL days. This change could be linked to the
variation in the charge center's vertical location during those months.
The diurnal cycle in the lightning activity was examined for each synoptic
system. During WCL conditions, no preferred times were found through the day,
as it relates to the random passage timing of the frontal systems over the
study region. During the fall systems (FCL and RST-CL) there is a peak in
lightning activity during the morning hours, probably related to the
enhanced convection driven by the convergence between the eastern land
breeze and the western synoptic winds. The distributions of peak currents in
FCL and WCL systems also change from fall to winter and include more strong
negative and positive strokes toward the end of the winter. |
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