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A 15-Year Climatology of Desert Dust Episodes in the Broader Mediterranean Basin
Maria Gavrouzou * 1 , Nikos Hatzianastassiou 2 , Antonis Gkikas 3 , Nikos Mihalopoulos 4, 5
1  Laboratory of Meteorology and Climatology, Department of Physics, University of Ioannina
2  ) Laboratory of Meteorology and Climatology, Department of Physics, University of Ioannina
3  Institute for Astronomy, Astrophysics Space Applications and Remote Sensing, National Observatory of Athens, Athens, Greece
4  ) Institute for Environmental Research and Sustainable Development (IERSD), NOA, Athens, Greece
5  Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Greece

Published: 13 November 2020 by MDPI in The 3rd International Electronic Conference on Atmospheric Sciences session Aerosols
10.3390/ecas2020-08138
Abstract:

Dust is the Earth’s most abundant aerosol type, mostly originating from great deserts (Sahara, Taklimakan, Gobi, Middle East), but also from agricultural and construction activities. The emitted dust remains in the atmosphere from a few hours up to several days, while under favorable conditions is transported far from its sources. During this transport, the physical and chemical properties of dust can change, thus affecting its action as Cloud Condensation Nuclei (CNN) or Ice Nuclei (IN) as well as its interaction with radiation, consequently modifying the radiation and energy budget of the areas affected by the dust transport. There is need for improving scientific knowledge about dust transport, especially over areas like the Mediterranean basin (MB), which is close to the Sahara, Middle East, and Arabian deserts, and frequently undergoes dust transport, resulting in dust aerosol episodes (DAE). In the present study, DAEs in the broader MB are investigated over a 15-year (2005-2019) period using contemporary MODIS Collection 6.1 and OMI OMAERUV satellite data and a satellite algorithm applying a thresholding technique on selected aerosol optical properties. The algorithm operates on a daily and 1°x1° pixel level basis, first identifying the presence of dust, and consequently requiring the presence of unusual high dust loads, i.e. dust episodes. Apart from the presence of pixel level DAEs, an extended spatial coverage is also required. Thus, a specific day is characterized as a Dust Aerosol Episode Day (DAED), when at least 30 episodic pixels exist. According to the algorithm results, 166 DAEDs (116 strong and 50 extreme) took place in the MB from 2005 to 2019. The greatest part of DAEDs occurred in spring (47%) and summer (38%), while a different seasonality is observed for strong and extreme episodes. The interannual variability of DAEDs reveal a decreasing trend, which is not statistically significant.

Keywords: aerosols; dust; Mediterranean; dust episodes; satellite data
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