Abstract
This study assessed the aerosol climatology over Iran, based on the monthly data of aerosol optical depth (AOD) derived from the reanalysis-based Modern Era Retrospective Analysis for Research and Applications (MERRA-2) and the satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS). In addition, sea level pressure, wind speed, temperature, relative humidity, precipitation, and soil moisture from the ERA5 reanalysis dataset were applied to investigate the climate-related effects on temporal AOD changes. Our analysis identified positive and negative AOD trends during 2000–2010 and 2010–2018, respectively, which are likely linked to aeolian dust changes. The dust-driven AOD trends were supported by changes in the Ångström exponent (AE) and fine mode fraction (FMF) of aerosols over Iran. During the early period (2000–2010), results of AOD-meteorology correlation analyses suggest reduced soil moisture, leading to increased dust emissions, whereas our results suggest that during the later period (2010–2018) an increase of soil moisture led to decreased AOD levels. Soil moisture appears to be a key factor in dust mobilization in the region, notably in southwestern Iran, being influenced by adjacent mineral dust sources. These phenomena were affected by large-scale sea level pressure transformations and the associated meteorology in the preceding winter seasons. Using a multiple linear regression model, AOD variability was linked to various meteorological factors in different regions. Our results suggest that climatic variations strongly affect the dust cycle, with a strong dependence on wintertime conditions in the region.
Highlights
Atmospheric aerosols are an important component in the Earth system [1] and significantly influence global and regional climate change, clouds and precipitation, air quality, and public health [2,3,4,5]
Significant positive trends were found in the MERRA-2 and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD), with a small difference in small areas, mainly related to using different versions of AOD collections [10,13,23]
In compared with AOD trends (Figure 2) can be seen in the north and west of Iran in the contrast, significant downward trends were detected in the later period by using both AOD
Summary
Atmospheric aerosols are an important component in the Earth system [1] and significantly influence global and regional climate change, clouds and precipitation, air quality, and public health [2,3,4,5]. The variability of meteorological factors plays a major role in determining AOD trends over dust-dominated regions such as the Sahara and Middle East deserts [23,24,25,26]. Trends of these variables and the role of the preceding winter meteorology (DJFM) on AOD during the dusty period (MJJA) are analyzed.
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