Temporal-Spatial Analysis of Thunderstorms in Iran

Thunderstorm is a major climatic hazard that puts a lot of damage to different sectors. Therefore, evaluation of its spatial-temporal characteristics can help a lot to understand the rules of its occurrence and determine the potential of different regions. The aim of this study is to analyze the spatial-temporal characteristics of thunderstorms in Iran based on the latest hourly data. For this purpose, the hourly data of thunderstorms from 42 synoptic stations in 7 different status, from precipitation to dusty and heavy hail, 8 times a day were obtained from Iranian Meteorological Organization in a 37-year period (1980-2016). Then using cluster analysis, the country was divided into four zones based on the frequencies, and the occurrence of phenomenon in each zone was analyzed. Then, using the Mann-Kendall, linear regression and Sen's slope estimator statistical tests, the temporal trend of the phenomenon was investigated in the country. The results showed that the most thunderstorms occur in northwest and west of the country, around Urmia, Tabriz, Khoy and Khorramabad stations, and also south of the country around Bushehr station. In seasonal and monthly scales, the highest frequency can be seen in the spring with a maximum of May. In spring, northwest, in summer, northern coasts and northwest, in fall, southwest and west, and in winter, southern coasts and southwest of the country experience more thunderstorms. In hourly scale, it became clear that the storm would be delayed due to the regions’ temperatures. Hence in warm regions it happens in the sunrise and early morning, and in cold regions in the sunset and early evening. But in general, thunderstorms are more frequent in 21:30 local time and then with a slight difference, in 18:30. In most stations the number of thunderstorms is increasing.