Aerosol optical thickness over large urban environments of the Arabian Peninsula-speciation, variability, and distributions

The Arabian Peninsula is one of the world's largest sources of mineral dust that includes several major population hotspots. However, until now, few studies have performed a comprehensive quantification of the long-term variability of aerosol species in this region. In this study, the speciation, variability, and distribution of aerosol optical depth over the Arabian Peninsula during 2005-2015 is analyzed by using the modern-era retrospective analysis for research and applications, Version 2 (MERRA-2) model together with satellite retrieved data and AERONET observations and focusing on nine large cities in the region (Dammam, Doha, Dubai, Jeddah, Kuwait, Manama, Muscat, Riyadh, and Sanaa). Over the past decade, the mean annual aerosol optical thickness (AOT) values were in the range of 0.3-0.5, which is attributed to both mineral dust (60-70%) and anthropogenic activities (20-30%). An increase in AOT values between 2005 and 2009 is attributed to increased dust generation from the Sahel region in Northern Africa, and the Fertile Crescent (Syria, Iraq, Jordan) due to an extended dry period. Reductions in local urban emissions are still considered to be efficient measures to improve air quality in these population centers despite the significant contribution of desert dust in the total particulate matter levels in the region.