Extended Abstract
Introduction: Dust storms are a consequence of desertification and land degradation, particularly in arid and hyper-arid regions worldwide. The factors influencing the spatial distribution of dust storms are largely dependent on altitude and latitude. Among natural disasters, droughts stand out as climatic anomalies that develop gradually and insidiously, exerting pressure on various societies. Drought can significantly affect the conditions and characteristics of dust storms. The primary objectives of this research are to examine the temporal and spatial distribution of dust storms in Ilam and Khuzestan provinces, and to explore the relationship between meteorological drought characteristics and the occurrence of dust storms in these regions.
Materials and Methods: This study investigates the temporal and spatial variations of dust storms and the impact of drought characteristics on them during the statistical period of 1989-2019. The characteristics of drought were identified using the Standardized Precipitation Index (SPI) method. Dust storm data were extracted from synoptic station records related to the horizontal visibility on dusty days. Monthly, seasonal, and annual distributions of dust storms were analyzed. The trends in dust storms, precipitation, and temperature changes were determined using the Mann-Kendall method and Sen's slope estimator. Additionally, satellite images from the MODIS sensor were analyzed for days associated with dust storms, and the Aerosol Optical Depth (AOD) and Normalized Difference Dust Index (NDDI) were derived. The relationship between drought characteristics and dust storm characteristics was then assessed using correlation and linear regression analyses, and the effects of drought on dust storm occurrences were examined.
Results and Discussion: The years 1990, 1995, 2007, 2008, 2010, 2011, and 2017 experienced widespread droughts, with 2008 recording the highest drought intensity and extent. Meteorological data indicated that January and August, as well as the winter and autumn seasons, had the highest and lowest incidences of dust storms, respectively. According to the AOD index, April and December, and the spring and autumn seasons, exhibited the highest and lowest dust storm occurrences, respectively. During the studied period, the frequency of dust storms increased at 11 stations and decreased at 8 stations. The trend of maximum temperature was upward at all stations, while minimum temperature trends were upward at most stations. Precipitation trends were generally decreasing across the studied stations. The NDDI index provided a good estimate of regional dustiness, although in some cases, the index data did not align with ground observations and contained significant errors. Statistical tests revealed correlations between maximum temperature, minimum temperature, and precipitation data. However, the AOD index generally showed no correlation with other variables.
Conclusion: The analysis of the relationship between drought characteristics and dust storms indicated that 2008 saw the most frequent and severe dust storms, as well as the most widespread drought, though this trend was not consistent in other years with widespread droughts. Comparing Ilam and Khuzestan provinces, it was observed that southwest Ilam, which borders Khuzestan, shares similar dust storm characteristics due to comparable topography and climatic conditions. Overall, there is a significant difference in the intensity and frequency of dust storms between the two provinces, largely due to Ilam's mountainous terrain, especially in its central and northern regions. Additionally, it appears that the primary source of dust storms in the region originates from neighboring countries southwest of Iran. The flatness of the Khuzestan plain also contributes significantly to the intensity of wind activity, leading to higher frequency and severity of dust storms.