Document Type : Research Article
Authors
1 Department of Climatology, Mohaghegh Ardabili University, Ardabil, Iran
2 Department of Climatology, Kharazmi University, Tehran, Iran.
Abstract
Iran is a country that is faced with storms, thunderstorms, hail and floods every year. Therefore, in the present study, the temporal and spatial distribution and synoptic and thermodynamic analysis of the thunder storm occurrence in a large part of the Iran have been addressed. For this purpose, the data related to days with a thunderstorm of 20 synoptic stations in the eastern part of the Iran and geopotential heights (hgt), omega and specific moisture content (shum) data were used during the statistical period (2010-2015). After extraction of days with thunderstorms, ArcGIS software and IDW method were used for the temporal and spatial distribution maps. Then, using GrADS software synoptic maps were prepared and analyzed for different levels of atmosphere. Also, for the thermodynamic analysis, the Skew-t charts and CAPE and PWAT indices were used. The results of the temporal and spatial distribution have showed that from Jiroft city in the province of Kerman to the high latitudes in April and May, the highest frequency of thunder storms is observed and to the lower latitudes from December to February, there are a lot of thunder storms. In the northern part of the study area, the most frequent occurrence is in the spring and in the southern part of the region, the most occurrences occur in the winter. In total, in all the study areas throughout the year, there is shortly thunderstorm event. The results of the synoptic analysis also showed that during the days with thunderstorms, the negative omega and the ascending and unstable air, and on the other hand, the influence of moisture on the atmosphere of the area and the placement under the cut of low and the front of the Trough, conditions for the occurrence of this Provides a phenomenon. Investigating the skew-t charts and the CAPE and PWAT indices also indicate that there is more humidity in storm day than the day before the storm and the instability resulting from a severe convective rise (about twice) on the day of thunderstorm.
Graphical Abstract
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