Publications

Sabetghadam, S; Alizadeh, O; Khoshsima, M; Pierleoni, A (2021). Aerosol properties, trends and classification of key types over the Middle East from satellite-derived atmospheric optical data. ATMOSPHERIC ENVIRONMENT, 246, 118100.

Abstract
Aerosol optical properties have been analyzed to investigate seasonal and regional variability of aerosols and to classify their key types over the Middle East during the period 2001-2019. The collection 6.1 MODIS aerosol products are used, including daily values of aerosol optical depth (AOD) and the Angstrom exponent (AE) data. The MODIS aerosol retrievals are verified using measurements from ten ground-based sunphotometers of the AErosol RObotic NETwork (AERONET). Overall, a good agreement between the two datasets is found. Nevertheless, an overestimation of the MODIS retrievals is found in most regions. Seasonal comparison reveals that aerosol loading ranges between 0 and 0.7, with a distinct geographical variability. The highest value of AOD is found over the Arabian Peninsula especially during warm seasons. The second maximum value of AOD is located over an area stretching from southeastern Iran to western Pakistan, with higher values during summer. The lowest AOD values are found over countries in the northern part of the studied region, including Turkmenistan, Uzbekistan, Kazakhstan, Armenia and Georgia, as well as some over parts of Turkey. Regions with the highest aerosol loads are accompanied with the lowest AE values. Coarse marine particles are dominant in coastal regions in southern Iran across the Persian Gulf. There is an increasing trend of AOD values, reaching to 0.05 per decade over the Arabian Peninsula and the northern coast of the Caspian Sea in all seasons, while negative trends are found in Pakistan, south Afghanistan, west coast of the Black Sea and northeast of Africa. During cold seasons, AOD does not vary as much as that in warm seasons. Aerosols have been classified using the critical values for AOD and AE. Results show the dominance of mixed type aerosols in all seasons over the region. In spring and summer, desert dust is the second-highest contributor to aerosol composition, followed by urban aerosols. Maritime-like aerosols transported from the Caspian Sea and the Aral Sea are present mostly during autumn. Uzbekistan, Turkmenistan and western parts of Kazakhstan commonly experience a relatively clean atmosphere during the whole year, except for episodic dust storms in summer. Smoke has a small undetectable contribution to the studied region.

DOI:
10.1016/j.atmosenv.2020.118100

ISSN:
1352-2310