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| Titel |
Instability indices and forecasting thunderstorms: the case of 30 April 2009 |
| VerfasserIn |
S. Tajbakhsh, P. Ghafarian, F. Sahraian |
| 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 Science ; 12, no. 2 ; Nr. 12, no. 2 (2012-02-17), S.403-413 |
| Datensatznummer |
250010509
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| Publikation (Nr.) |
 copernicus.org/nhess-12-403-2012.pdf |
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| Zusammenfassung |
In this paper, one meteorological case study for two Iranian airports are
presented. Attempts have been made to study the predefined threshold amounts
of some instability indices such as vertical velocity and relative humidity.
Two important output variables from a numerical weather prediction model
have been used to survey thunderstorms. The climatological state of thunder
days in Iran has been determined to aid in choosing the airports for the case
studies. The synoptic pattern, atmospheric thermodynamics and output from a
numerical weather prediction model have been studied to evaluate the
occurrence of storms and to verify the threshold instability indices that
are based on Gordon and Albert (2000) and Miller (1972).
Using data from the Statistics and Data Center of the Iran Meteorological
Organization, 195 synoptic stations were used to study the climatological
pattern of thunderstorm days in Iran during a 15-yr period (1991–2005).
Synoptic weather maps and thermodynamic diagrams have been drawn using data
from synoptic stations and radiosonde data. A 15-km resolution version of
the WRF numerical model has been implemented for the Middle East region with
the assistance of global data from University Corporation for Atmospheric
Research (UCAR).
The Tabriz airport weather station has been selected for further study due
to its high frequency of thunderstorms (more than 35 thunderstorm days per
year) and the existence of an upper air station. Despite the fact that
storms occur less often at the Tehran weather station, the station has been
chosen as the second case study site due to its large amount of air traffic.
Using these two case studies (Tehran at 00:00 UTC, 31 April 2009 and Tabriz at
12:00 UTC, 31 April 2009), the results of this research show that the threshold
amounts of 30 °C for KI, −2 °C for LI and −3 °C for SI suggests
the occurrence and non-occurrence of thunderstorms at the Tehran and Tabriz
stations, respectively. The WRF model output of vertical velocity and
relative humidity are the two most important indices for examining storm
occurrence, and they have a numerical threshold of 1 m s−1 and 80%,
respectively. These results are comparable to other studies that have
examined thunderstorm occurrence. |
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