Abstract
Dust storms represent a major environmental challenge in the Middle East. The southwest part of Iran is highly affected by dust events transported from neighboring desert regions, mostly from the Iraqi plains and Saudi Arabia, as well as from local dust storms. This study analyzes the spatio-temporal distribution of dust days at five meteorological stations located in southwestern Iran covering a period of 22 years (from 1997 to 2018). Dust codes (06, 07, 30 to 35) from meteorological observations are analyzed at each station, indicating that 84% of the dust events are not of local origin. The average number of dust days maximizes in June and July (188 and 193, respectively), while the dust activity weakens after August. The dust events exhibit large inter-annual variability, with statistically significant increasing trends in all of five stations. Spatial distributions of the aerosol optical depth (AOD), dust loading, and surface dust concentrations from a moderate resolution imaging spectroradiometer (MODIS) and Modern-Era Retrospective analysis for Research and Applications (MERRA-2) retrievals reveal high dust accumulation over southwest Iran and surrounding regions. Furthermore, the spatial distribution of the (MODIS)-AOD trend (%) over southwest Iran indicates a large spatial heterogeneity during 2000–2018 with trends ranging mostly between −9% and 9% (not statistically significant). 2009 was the most active dust year, followed by 2011 and 2008, due to prolonged drought conditions in the fertile crescent and the enhanced dust emissions in the Iraqi plains during this period. In these years, the AOD was much higher than the 19-year average (2000 to 2018), while July 2009 was the dustiest month with about 25–30 dust days in each station. The years with highest dust activity were associated with less precipitation, negative anomalies of the vegetation health index (VHI) and normalized difference vegetation index (NDVI) over the Iraqi plains and southwest Iran, and favorable meteorological dynamics triggering stronger winds.
Highlights
Ilam presents the highest increasing rate in the number of dust days (4.59 per year), while the increasing rates for the other stations range between 1.35 in Bushehr and 2.99 in Abadan (Figure 2). This indicates an important increase in dust activity over southwest Iran, which was found in the neighboring regions of the Middle East, such as Iraqi plains, Syrian desert, Persian Gulf, and nearly whole Saudi Arabia based on moderate resolution imaging spectroradiometer (MODIS) observations from 2000 to 2015 [32]
This study examined the long-term variation and trends of dust days and dust characteristics over the southwest part of Iran, based on synergy of meteorological data at five cities in the region and satellite observations
The dust presence was identified from meteorological observations of the dust synoptic codes (06, 07, and 30 to 35) at five stations (Ahvaz, Abadan, Bushehr, Ilam, and Kermanshah) highly impacted by local, regional, and long-range transported dust events throughout the year, but with higher frequency and intensity in spring and summer
Summary
The frequency and intensity of SDS have increased during the last few decades in some desert areas, as a result of human intervention and climate change, posing a main challenge to accomplish sustainable development in the affected regions [30] This increasing trend in dust activity is especially important in the Middle East during the last two decades [31,32,33,34,35,36]. Factors that facilitate this increasing trend include intensified land degradation and increased soil disturbance, desertification, and climate change [37,38,39], which are associated with socioeconomic impacts and triggering a feedback cycle of environmental degradation [40,41,42]. Previous studies have analyzed the long-term variability of dust events over SW Iran [52,87,88,89], the current work provides a comprehensive analysis combining ground measurements at five stations with satellite and re-analysis observations and regional meteorology, and differentiates the local and regional dust events
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