عنوان مقاله [English]
نویسنده [English]چکیده [English]
Thunderstorms are one of the climatic phenomenon that due to their accompaniment with thunder, lighting, gust wind, etc. and in addition to their positive effects, they can produce significant damages in the worldwide. The geographic position of Iranian plateau in middle latitudes, caused tropical systems, subtropical systems and extra tropical systems to effect at spatial time. Coming some of these systems influenced the frequency of occurrence this phenomenon. Moreover, The frequency of occurrence this phenomenon reduced or increased in certain hours, due to changing the Earth's surface temperature during the day. Thus, the temporal analysis of thunderstorms can contribute to the improvement of the predictions as well as the reduction of the disaster's impact. Therefore, the current weather (ww) hourly data related to Thunderstorm, but no precipitation and Thunderstorm (with or without precipitation) (codes17, 29), Thunderstorm, slight or moderate, without hail, but with rain and/or snow and Thunderstorm, slight or moderate, with hail (codes 95,96), Thunderstorm, heavy, without hail, but with rain and/or snow and Thunderstorm, heavy, with hail (codes 97,99), Thunderstorm combined with duststorm or sandstorm (98) were provided for46 synoptic stations. These data are related to a twenty- three statistical period (1986-2009). The frequency of occurrence in monthly scale and hourly scale has been calculated. The results show that the highest frequencies codes 17, 29 is related to June at 00:30 Am, codes 95,96 is related to May at 15:30 Pm, codes 97,99 is related to June at 03:30 Am, and code 98 is related to October at 18:30 Pm.