Kaskaoutis, DG; Kambezidis, HD; Badarinath, KVS; Kharol, SK
Dust storms are considered natural hazards, which affect ecosystems for a short interval of time ranging from a few hours to a few days. Due to the significant impact of dust outbreaks on climate, human health and ecosystems, numerous studies have been conducted throughout the world with differing instrumentation and techniques focusing on the investigation about such events. The identification of the dust aerosol sources is a difficult process due to the complex natural and anthropogenic processes, which are involved in entraining soil particles into the atmosphere during a dust transport. Monitoring of these particles is only possible from satellites because ground-based measurements are very limited in space and time. Focusing mainly on the Sahara desert, this chapter provides a short review on the recent knowledge about the dust aerosol optical and physico-chemical properties, the seasonal variability of dust outbreaks, the dust source regions, the main pathways towards Southern Europe, which is mostly influenced, and the main results of similar studies. Furthermore, this work analyzes a new methodology for the dust transport monitoring using a combination of satellite data and back-trajectories for the identification of coarse-mode aerosols, Sahara dust (SD) events and their transport mechanisms. The work covers a 6-year (2000-2005) period of daily aerosol optical depth at 550 nm (AOD550) and fine-mode (FM) fraction values, derived from Terra-MODIS observations. Based on the AOD550-FM relation, the cases satisfying the criterion AOD550>0.3 and FM<0.6 refer to coarse-mode aerosols, probably categorized as dust particles. A specific application is made to the Athens area. Back-trajectories ending at Athens at altitudes of 500, 1000 and 4000 in are calculated by means of the HYSPLIT model. The majority of the SD events over Athens occur in April-May and July, while very few in November-December. The average number of the SD events per year is about 13, with a maximum of 20 in 2002 and a minimum of 7 in 2003. The Aerosol Index (AI) derived from TOMS is found to adequately characterize the dust load over Athens despite the fact that 35% of the dust cases conforming with the back-trajectory analysis do not correspond to high (above 0.5) AI values. As a conclusion, this work shows that the combination of remote-sensing measurements and back-trajectory analysis constitutes a powerful tool for the identification of SD events over Athens, and to a certain extend at other locations around the Mediterranean region, since the results are found to be in agreement with those of relevant studies.