Temporal and spatial distribution of thunderstorm days considering raising temperature in northwestern Iran (1997-2016)

The purpose of this paper is to investigate the change of thunderstorm days during the warming of the atmosphere over the past two decades in northwestern Iran. Therefore, the statistical analysis of temperature changes at a height of 2 meters and the number of thunder days are discussed. This study was carried out using the 57 synoptic meteorological observation stations data in the northwestern region of Iran. Observation data included temperature and thunderstorm synop reports that were available every 3 hours. The most important results of this study show that thunderstorms occurred in Spring, Autumn, Summer and Winter seasons, respectively over the northwest of Iran. Hence, it seems that thunderstorms classified as the air mass thunderstorm in northwestern Iran. The city of Maku, with an average of 14 thunderstorm days per year, had the highest number of stormy days in the northwestern region of Iran. The average number of thunder days is 10.1 days, and the maximum and minimum values of thunder days were 28 and 0.7 days, respectively. The number of thunder days grew substantially over 20 years (1997-2016) investigation. This situation accompanied by a temperature rising during the same period of thunder days (0.5°C during 20 years) in Northwestern Iran. It seems that raising of the Earth s atmosphere temperature affected the number of atmospheric hazards of thunderstorms.