Document Type : Research Paper

Authors

• Fatemrh Dargahian ¹
• Azadeh Gohardoust ²
• Sakineh Lotfinasabasl ³
• Sara Teimouri ⁴

¹ Associate Professor, Research institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

² Researcher, Desert research division, Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.

³ Assistant Professor, Research institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Iran

⁴ Assistant Professor, Poplar and fast growing trees Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Terhran, Iran.

Abstract

Background and Objectives
Numerous studies have individually examined the influence of neighboring countries on dust generation in southwestern Iran (Khuzestan). However, the specific countries and regions within those countries with the most significant impact on dust events in the southwest still need to be clarified. This study aimed to identify the primary sources of dust emissions affecting Khuzestan using the Aerosol Optical Depth (AOD) index for dust detection and the HYSPLIT model for tracing dust pathways.
Methodology
Dust events in Khuzestan province from 2003 to 2017 were identified using MODIS imagery and a suitable dust detection algorithm. Three criteria were applied to each event: spatial extent exceeding 50% of synoptic stations, horizontal field of view less than 5 km, and detection in at least three consecutive synoptic reports. Considering typical dust ingress into Iran at lower and middle atmospheric layers, dust pathways were investigated at 500, 1000, and 1500 meters above ground level. HYSPLIT model outputs for dust event days were combined with AOD images from each year's day before the event in Khuzestan. Areas with the highest dust emissions towards Khuzestan were identified by analyzing AOD concentrations in the days preceding dust events. Regions exceeding a threshold of 30 times the AOD concentration were designated as dust sources or intensification zones. This analysis was performed for each year and the entire period, allowing for prioritization of the most significant dust source areas.
Results
Our analysis of dust events revealed that different regions dominated dust emissions toward Khuzestan across the study period. In 2003, northern and eastern Arabia contributed the most dust. Subsequent years exhibited varying source regions, including the Iraq-Syria border (2004), Saudi Arabia (2005), southern Iraq (2006), southern and southeastern Iraq (2007-2008), southwestern Iraq and northern Iraq alongside northern and eastern Arabia (2009), southern and southwestern Iraq (2010), western, southern, and northern/eastern Iraq alongside Arabia (2011), and again southern and southwestern Iraq (2012-2013). In 2014 and 2015, northern and eastern Arabia re-emerged as the primary source. Finally, the Iraq-Syria border, western Iraq, and southern Iraq were identified as dominant sources in 2016 and 2017, respectively. Across the entire study period (2003-2017), eastern Iraq, the Iraq-Syria border, southern Iraq, and northern and eastern Arabia emerged as the most significant dust source regions impacting Khuzestan.
Conclusion
Our analysis revealed that Iraq contributes the highest proportion of dust emissions impacting Khuzestan province (68.8%), followed by Saudi Arabia, Syria, and Kuwait. Considering anticipated climate change and intensified dam construction activities in upstream countries, particularly Iraq, dust generation will likely worsen. The dust originating from these regions, situated along the path of synoptic systems towards Iran, has significantly impacted the environment, especially the Zagros forests. Identifying the primary dust source areas empowers policymakers to develop tailored and effective diplomatic strategies for controlling and mitigating the effects of regional fine dust.

Keywords

• Neighboring countries
• Origin of dust
• Modis images
• HYSPLIT model
• Tracking