Temporal variations in the frequency and concentration of dust events over Iran based on surface observations

Abstract

Using surface meteorological records of a 20-year period from 1991 to 2010, temporal variations in the frequency and concentration of transported dust events over Iran are investigated. Five regions of frequent dust events are identified. In the order of importance, these areas are the Khuzestan Plain, the coastal plain of the Persian Gulf, west of Iran, Tabas and Sistan. The first three areas create a belt of high frequency of dust events along the western foothills of the Zagros Mountains. The Khuzestan Plain is the area with the highest frequency of dust events, over which dust laden air is almost permanently present in summer, while the coastal plain of the Persian Gulf is the second most affected area. These two areas, along with west of Iran, are mostly influenced by transported dust from sources outside of Iran, while Tabas and Sistan are mostly influenced by arid lands in the interior of Iran. In contrast, the southern coastal strip of the Caspian Sea is the area with the least frequent dust episodes. Throughout Iran, the frequency of dust events strengthens in spring, peaks in summer and significantly weakens in autumn and winter, with the least observed frequency in winter. Significant monthly variations of the frequency of dust events were also identified, with the most and least frequencies in July and December, respectively. In terms of long-term frequency of dust events, our observational analyses show an overall rising trend of the frequency of Iran's dust events in recent years, predominantly attributed to increasingly frequent dust outbreaks in Iraq due to human intervention.

Interannual variations of dust activity in western Iran and their possible mechanisms

“…The regional mean precipitation, wind speed and maximum wind speed are also shown in Figure 3(a) to illustrate the reasons for the seasonal variations in the DDF. The observations show that 75% of yearly dust events occur in the months of March to August when the monthly DDF is above 15%, which is consistent with previous studies (Alizadeh-Choobari et al, 2016;Doabi, Afyuni, & Karami, 2017;Nabavi et al, 2016;Sarraf, Rasouli, Mohammadi, & Sadr, 2016). The DDF is lowest in December (4%), and after January, it begins to increase and peaks in June and July (33%), followed by a decrease from August to December.…”

“…Observations have shown a high frequency of dust storms in the western and southeastern parts of Iran (e.g., Cao, Liu, Wang, Yang, & Luo, 2015;Middleton, 2019;Modarres & Sadeghi, 2018), and the areas of western Iran, the Khuzestan Plain and the coastal plain of the Persian Gulf in southwestern Iran (the study areas in this research) constitute a regional belt of high-frequency dust outbreaks (Alizadeh-Choobari, Ghafarian, & Owlad, 2016). The high frequency of dust storms in these regions has been attributed to several factors, including low vegetation cover in the arid lands in Iran (Broomandi, Dabir, Bonakdarpour, & Rashidi, 2017a;Esmaili, Tajrishy, & Arasteh, 2006;Najafi et al, 2014), recent droughts in western Iran (Zoljoodi, Didevarasl, & Saadatabadi, 2013), and dust transportation from other regions (e.g., Alizadeh-Choobari et al, 2016;Yu, Notaro, Kalashnikova, & Garay, 2016). The seasonal variations of dust events in western Iran are remarkable, and the highest frequency of dust events is found in summer, when strong Shamal winds are persistent and little precipitation is received (Alizadeh-Choobari et al, 2016).…”

“…There are large interannual variations in dust event frequency in Iran, as shown in several previous studies (e.g., Alizadeh-Choobari et al, 2016;Rashki, Arjmand, & Kaskaoutis, 2017). There are concerns as to why dust activity varies interannually, and whether natural or anthropogenic factors can intensify dust storm occurrences and, consequently air pollution, in the western provinces of Iran (Zoljoodi et al, 2013).…”

“…The high frequency of dust storms in these regions has been attributed to several factors, including low vegetation cover in the arid lands in Iran (Broomandi, Dabir, Bonakdarpour, & Rashidi, 2017a;Esmaili, Tajrishy, & Arasteh, 2006;Najafi et al, 2014), recent droughts in western Iran (Zoljoodi, Didevarasl, & Saadatabadi, 2013), and dust transportation from other regions (e.g., Alizadeh-Choobari et al, 2016;Yu, Notaro, Kalashnikova, & Garay, 2016). The seasonal variations of dust events in western Iran are remarkable, and the highest frequency of dust events is found in summer, when strong Shamal winds are persistent and little precipitation is received (Alizadeh-Choobari et al, 2016).…”

The 20–22 February 2016 Mineral Dust Event in Tehran, Iran: Numerical Modeling, Remote Sensing, and In Situ Measurements

“…Meanwhile, the most common method to study the dust storms in Iran is to use the ground‐based measurements and meteorological stations data. The study of the frequency, temporal changes of particulate concentration, and determination of the statistical parameters of dust events in southeast (Rashki, deW Rautenbach, et al, ), southwest (Azizi et al, ; Shahsavani et al, ; Zarasvandi et al, ), and whole of Iran (Alizadeh Choobari et al, ); the evaluation of the effect of meteorological conditions on dust storms in Ahwaz (Shahsavani et al, ) and Sistan plain (Rashki et al, ); the determination of the elemental, mineral, metal, and microbiological compounds of mineral dust aerosols in western and southwestern cities (Najafi et al, ; Shahsavani et al, ; Zarasvandi et al, ); the classification of the areas prone to dust production based on geological and precipitation maps in the Middle East (Gerivani et al, ) and the study of the effect of land use changes of Hamun basin on dust storm created in Sistan plain (Rashki, Kaskaoutis, et al, ) were among the subjects studied by analyzing the data of in situ measurements.…”