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| Titel |
Numerical modeling and analysis of the effect of complex Greek topography on tornadogenesis |
| VerfasserIn |
I. T. Matsangouras, I. Pytharoulis, P. T. Nastos |
| 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 ; 14, no. 7 ; Nr. 14, no. 7 (2014-07-30), S.1905-1919 |
| Datensatznummer |
250118551
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| Publikation (Nr.) |
 copernicus.org/nhess-14-1905-2014.pdf |
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| Zusammenfassung |
Tornadoes have been reported in Greece over recent decades in specific
sub-geographical areas and have been associated with strong synoptic forcing.
While it has been established that meteorological conditions over Greece are
affected at various scales by the significant variability of topography, the
Ionian Sea to the west and the Aegean Sea to the east, there is still
uncertainty regarding topography's importance on tornadic generation and
development.
The aim of this study is to investigate the role of topography in significant
tornadogenesis events that were triggered under strong synoptic scale forcing
over Greece. Three tornado events that occurred over the last years in Thebes
(Boeotia, 17 November 2007), Vrastema (Chalkidiki, 12 February 2010) and
Vlychos (Lefkada, 20 September 2011) were selected for numerical experiments.
These events were associated with synoptic scale forcing, while their
intensities were T4–T5 (on the TORRO scale), causing significant damage. The
simulations were performed using the non-hydrostatic weather research and
forecasting model (WRF), initialized by European Centre for Medium-Range
Weather Forecasts (ECMWF) gridded analyses, with telescoping nested grids
that allow for the representation of atmospheric circulations ranging from
the synoptic scale down to the mesoscale. In the experiments, the topography
of the inner grid was modified by: (a) 0% (actual topography) and
(b) −100% (without topography), making an effort to determine whether
the occurrence of tornadoes – mainly identified by various severe weather
instability indices – could be indicated by modifying topography. The
principal instability variables employed consisted of the bulk Richardson
number (BRN) shear, the energy helicity index (EHI), the storm-relative
environmental helicity (SRH), and the maximum convective available potential
energy (MCAPE, for parcels with maximum θe). Additionally, a model
verification was conducted for every sensitivity experiment accompanied by
analysis of the absolute vorticity budget.
Numerical simulations revealed that the complex topography constituted an
important factor during the 17 November 2007 and 12 February 2010 events,
based on EHI, SRH, BRN, and MCAPE analyses. Conversely, topography around the
20 September 2011 event was characterized as the least significant factor
based on EHI, SRH, BRN, and MCAPE analyses. |
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