Climatology of dust days in the Central Plateau of Iran

Dust storms are a major natural hazard to human health. Severe erosive storms in parts of the Central Plateau of Iran have made the situation very difficult for the inhabitants, to the extent that some areas have become depopulated. To better understand this phenomenon, dust day counts at 37 synoptic stations from 1999 to 2018 were analyzed. Dust days were most common in June, with 45% of the total number occurring in summer (June-August) and 34% in spring (March-May), and were more frequent since 2008, as compared to 1999-2007. While the spatial pattern of dust days was complex, the highest number tended to be in the southeast of the region. The stations with the most dust days, Zabol, Zahedan, and Arak, averaged 126 days, 74 days, and 73 days of dust per year, respectively. The statistical distributions that most often best fitted the time series of number of dust days (NDD) per year were Johnson SB, Log-Logistic 3-Parameter, and Burr. These fitted probability distributions were used to estimate different return period values for annual number of dust days. For example, Zabol and Sirjan stations had, respectively, the highest and lowest 2-year return period NDD values, 125 and 2 days, respectively. Overall, the spatial pattern of the NDD at different return periods indicated that southeastern Iran, as well as some northwestern and eastern portions of the study region, had particularly high values of NDD at longer return periods, while much of the northern and southwestern margins of the region have low NDD at all return periods. These results may be useful for informing the regional management of dust storms.