Temporal long-term variations in the occurrence of dust storm days in Iran

In this research, monthly data on the Frequency of Dust Storm Days (FDSD) of 44 synoptic stations of Iran during a 50-year period from 1968–2017 were used. Temporal variations in Iran's dust storms were investigated using hierarchical cluster analysis, linear regression methods, and nonparametric test of Mann Kendall. According to the cluster analysis, five climatic zones were identified with similar trends in the frequency of occurrence of dust storms including: (1) Southeast, (2) South and Central regions, (3) Western regions, (4) Eastern and Central regions, and (5) the Northern part of the country. The results of the distribution of Iranian dust storms indicated that the highest frequency of the occurrence of this phenomenon was in July, June, and May. In the seasonal period, the peak of the dust storms was concentrated in the spring and summer. Moreover, in terms of spatial analysis, in monthly, seasonal, and annual periods, the maximum FDSD in the southeastern and southern regions was much more severe than in other regions of Iran. Moreover, the slope of the changes in Iran's dust storms indicated that the trend of changes in total monthly, seasonal, and annual periods was incremental, and according to the results of the Mann–Kendall test, it was significant.