Document Type : Research Paper
Authors
1 Ph.D. Candidate in Agricultural Meteorology, Faculty of Agricultural Engineering, Agricultural Sciences and Natural Resources University, Sari, Iran
2 Assistant Professor, Department of Computer and Cybernetics, Faculty of Engineering and Aviation, Imam Ali (AS) Military University, Tehran, Iran
3 Ph.D., Department of Geography and Climatology, Faculty of Basic Sciences, Imam Ali (AS) Military University, Tehran, Iran
Abstract
Introduction
Dust storms have emerged as one of the most significant environmental challenges in arid and semi-arid regions, and their frequency and intensity have notably increased in Ilam Province in recent years. These storms have had wide-ranging impacts on public health, urban infrastructure, agriculture, and the sustainability of natural resources. The province’s geographical location along the borders of Iraq and Syria makes it particularly vulnerable to transboundary dust storms originating from desertified areas in neighboring countries. Accordingly, precise monitoring of the spatiotemporal dynamics of dust storms and identifying their sources are essential for developing effective mitigation strategies and reducing their adverse impacts.
Materials and methods
In this study, PM concentration data from 2020 to 2025 were collected from air quality monitoring stations in Mehran and Dehloran as ground-based observations. In parallel, satellite-based indices were utilized, including the Aerosol Optical Depth (AOD) from MODIS, the Absorbing Aerosol Index (AAI) from Sentinel-5P TROPOMI, the Normalized Difference Dust Index (NDDI), and the Dust Event Count Map (DECM). All datasets were processed and analyzed using Google Earth Engine. To track the transport pathways of dust plumes, the HYSPLIT model was applied with a 24-hour backward trajectory simulation. Additionally, MODIS True Color images were employed to visually validate the HYSPLIT model outputs.
Results and discussion
Analysis of the DECM index from 2020 to 2024 revealed an upward trend in the frequency of dust events in Ilam Province. In 2020, the lowest number of events was recorded, although even in that year, Dehloran and Abdanan experienced over 30 events. In 2021, the number rose to over 120 events in border regions, reaching a critical peak in 2022 with more than 200 dust events recorded in Mehran, Dehloran, Eyvan, and southern Ilam. Although the numbers slightly decreased to 182 and 172 in 2023 and 2024, respectively, the spatial concentration of dust activity remained in the border areas. The Absorbing Aerosol Index (AAI) extracted from Sentinel-5P data further confirmed the severity of the situation. In 2020, the mean AAI values in Mehran, Dehloran, and Abdanan were around 0.28, increasing to 0.32 in 2021, and exceeding 1.3 in 2022 -indicative of very unhealthy conditions for the general population. Despite slight declines in 2023 (0.87) and 2024 (0.86), values remained in the unhealthy range. MODIS-derived AOD data also played a key role in assessing dust intensity. In 2020, AOD levels surpassed 1 in border areas and exceeded 1.6 in some regions in 2021. The critical peak occurred in 2022, when AOD values reached over 1.85 in southern Ilam and western Dehloran. Even central parts of the province saw AOD values greater than 0.5 in the same year. In 2023 and 2024, the values were 1.3 and 1.18, respectively, remaining within hazardous levels. The NDDI index, which reflects dust deposition on surfaces, peaked in 2021 with values exceeding 0.9 in some border areas. In 2022, the index dropped to approximately 0.5, possibly indicating airborne dust with limited ground deposition. It reached its lowest point in 2023 (below 0.5), followed by a slight increase to 0.54 in 2024. The HYSPLIT model was used to simulate dust transport pathways for two critical events in 2025. On April 15, 2025, the model identified western Iraq as the main dust source. Simulations showed that the dust plume reached the Ilam border at 11:00 AM and Dehloran station by 12:00 PM. Vertical profiles indicated that dust particles initially traveled at 500 meters altitude and later descended into the boundary layer, corroborating the recorded AQI level of 500 in Dehloran. In the second event on May 25, 2025, the dust originated from the deserts of eastern Syria. The particles formed at an altitude of 2000 meters and traveled across Iraq, reaching Mehran station at 12:00 PM. The trajectory showed a gradual descent to 500 meters, leading to severe surface-level pollution. Trajectory frequency maps indicated that more than 90% of paths passed through Syria, confirming the combined influence of Iraqi and Syrian sources. This event also saw an AQI level of 500 in Mehran. Overall, the results underscore the spatial stabilization of dust hotspots in Ilam’s border regions and highlight the critical role of transboundary dust sources in Iraq and Syria, as well as the synoptic wind patterns that facilitate their transport.
Conclusions
The findings demonstrate a notable increase in the frequency and intensity of dust storms in Ilam Province in recent years, with a clear spatial concentration in border areas. Transboundary sources, particularly desert regions in Iraq and Syria, have significantly contributed to the worsening dust pollution. The integration of satellite indices with the HYSPLIT model enabled the precise identification of dust origins, transport paths, and intensity. Consequently, implementing control strategies such as the restoration of drought-resistant vegetation, soil stabilization, land moistening, establishment of greenbelts along the borders, enhancement of regional cooperation with neighboring countries, and deployment of satellite-based early warning systems is essential. Without such interventions, the current trajectory may lead to a chronic crisis and exacerbate environmental, social, and economic vulnerabilities in the region.
Keywords
)