# Regional Analysis of Dust Day Duration in Central Iran
###### Abstract  
The duration of dust days (DDD) is one of the most important parameters that may worsen the effects of the presence of dust in the affected areas. Persistent pollution over consecutive dusty days can have particularly negative effects on the human respiratory system. The present analysis was conducted in Central Iran, where the phenomenon of dust is one of the most important problems. In this study, using dust codes recorded at 35 synoptic stations, the homogeneity of DDD across the region was investigated using the L-moments method. Then, characteristics of DDD over the period 1999-2018 were calculated. The results showed that the region is statistically homogeneous. Furthermore, Zabol and Zahdan are the stations worst affected, with the longest durations of 22 and 21 days in 2014. Additionally, the values of DDD with return periods of 5, 10, 25, and 50 years were calculated using fitted statistical distributions and kriging and mapped. Finally, using the K nearest neighbor method the most important factor affecting DDD of the spatial characteristics, including longitude, latitude, elevation, average daily temperature (t\({}_{\text{m}}\)), dew point (t\({}_{\text{d}}\)), wind altitude (u), maximum wind speed (ff\({}_{\text{max}}\)), and direction of the fastest wind (dd\({}_{\text{max}}\)), was determined. It was found that the southeastern parts of the study area are affected by the longest dust storm duration in all return periods; over longer return periods, long dust storms are also found in the central parts, especially the central desert of Iran. Therefore, these areas should be given priority in fighting and controlling wind erosion. Furthermore, the results showed that the maximum wind speed has the greatest effect on DDD. duration of dust days; L-moments; easy fit; maximum wind speed; central plateau of Iran 4.0 (2022) 12 6248 10390/app12126248 10390/app12126248 10390/app12126248 10390/app12126248 10390/app120222 16 June 20  
impact on the atmosphere. It affects the radiation budget of the earth's atmosphere by scattering and absorbing solar radiation, alters cloud characteristics by providing cloud condensation nuclei or ice nuclei, and heats up the surrounding environment [6]. These particles can reduce air quality, favoring severe respiratory diseases, as well as destroy transportation infrastructure, reduce incoming solar radiation [7; 8], induce negative effects on vegetation and agricultural fields, and so on [9]. One of the major factors in the formation of dust storms is the presence of strong wind flows associated with low-pressure systems in potential source areas [10]. Dust particles are effective in absorbing and reflecting the sun and earth radiation, especially in layers below 3000 m, affecting the incoming and outgoing radiation at the earth's surface (atmospheric radiation balance). By increasing the absorption and reflection of sunlight towards space, they directly cool the underlying layers of the atmosphere and, on the other hand, warm the earth by trapping long wavelengths reflected from the earth's surface [3; 5; 11; 12; 13; 14; 15]. Dust particles are harmful and dangerous to public health [16]. Dust storms can transmit a variety of pollutants and allergens such as spores, fungi, bacteria, pathogenic viruses, sediments, heavy metals as well as radioactive materials [17]. Breathing polluted air causes respiratory disorders including asthma, bacterial infection of the trachea and bronchi, pneumonia, and cardiovascular disorders including stroke and heart attack [18]. As well, dust also has a significant impact on global biochemical cycles, soil formation, atmospheric chemical composition, and air quality [19; 20; 21; 22; 23]. Therefore, dust may have irreversible harmful effects, and any area that has a high number of consecutive dust days will have more harmful effects. Dust is a dynamic phenomenon and research on it covers a wide range of time scales and variability in frequency and intensity [24; 25; 26].