# Regional Analysis of Dust Day Duration in Central Iran
## 4 Discussion  
The phenomenon of dust is one of the most serious problems affecting the central plateau of Iran and this phenomenon has a very negative effect on the lives of the inhabitants of this region. One of the most important indicators determining the number of risks and damages of this phenomenon is its duration. A long duration of high dust concentration can have very detrimental effects on the respiratory system so a given level of dust can be very dangerous if accompanied by a long duration. Due to the presence of the main deserts of Iran (Loot Desert and Central Desert (Dasht-e Kavir)) in this region, the conditions for creating dust are very favorable. Ref. [36] also pointed to Middle East desert dust as an important risk factor for human health. That study found that the southeastern parts of the region, which are mostly located in the central Loot and Jazmourian basins, have the highest annual-maximum duration of dust days. Zabol and Zahdan are the stations having the highest duration of dust days in the region, being along the path of erosive winds such as the \"120-day\" Sistan storm pattern. Dry rivers and wetlands in this area, which includes the Helmand Basin, are considered the most important source of dust. Ref. [37] states that the southeastern region of Iran, which includes Sistan and Baluchestan provinces (Zahdan and Zabol stations), are the most important sources of dust in the central plateau of Iran. Ref. [38] also mentions this issue and states that the southeastern regions of Iran are affected by the deserts of Afghanistan and the Helmand Basin.  
In order to predict the areas affected by the longest DDD, maximum expected DDD values at return periods of 5, 10, 25, and 50 years were determined for the stations and regionalized via kriging. It was determined that the southeastern part of Iran for all return periods is the area where the dust phenomenon is most concentrated. However, with longer return periods, the desert in the central parts of Iran also faces considerable risks of long dust events. Ref. [39] analyzed the frequency of dust days in the central plateau of Iran and states that the southeastern parts of the basin have a high frequency in all return periods. Ref. [40] also states that the eastern part of Iran, Zabol station, has a high frequency of dust, and the existence of the Helmand plain and the 120-day winds of Sistan are the most important factors responsible for that. Ref. [41] showed that so-called shamal, levar, and monsoon winds highly control the formation and dynamics of dust regimes. The 120-day winds of Sistan are from the monsoon winds and blow from the southeast, most strongly affecting the area around Zabol and Zahdan stations [42]. [PERSON] [39] also found that Zabol station has the highest number of dust days in the region of the central plateau of Iran.  
One of the most important factors that cause the movement of dust masses is the wind. Consistent with this, the results of this study also showed that the maximum wind speed  
Figure 16: Character significance diagram for the k-NN method.  
has the greatest effect on the geographic distribution of dust duration across arid Central Iran. Windiness has also been postulated to be a key driver of interannual variability in dust day frequency in North Africa and China [40].