Characterising the long-range transport mechanisms of different aerosol types over Athens, Greece during 2000–2005

This study analyses the weather conditions, the main pathways and transport mechanisms favouring the presence of specific aerosol types over Athens, Greece. On the basis of the aerosol optical depth at 550 nm (AOD550) and fine mode (FM) values from a Terra-MODIS dataset in the period 2000–2005, three main aerosol types are identified (urban/industrial, UI; clean maritime, CM; and desert dust, DD), each one corresponding to different optical characteristics and source regions. The UI aerosols are associated with polluted air masses from Europe, the CM aerosols with clean Atlantic air masses and the DD aerosols with air masses from North African arid regions carrying significant amount of dust in certain cases. The comparison of the three aerosol types with the air masses from their favourable sector constitutes a first ‘quick-validation’ of the identification scheme. Thus, the incidence of transport from Europe explain 81% of the variability in the observed UI type, while the 73% of the Atlantic air masses correspond to the CM type; the 50% of the African air masses can be considered as DD aerosols over Athens. The mean synoptic meteorological patterns, favouring the presence of each aerosol type, are also investigated. Further analysing the air-mass trajectories at three altitudes, the transport mechanisms of the aerosol types are identified. The results clearly show that the UI aerosols are mainly transported within the boundary layer, while the CM conditions are associated with Atlantic air masses at higher altitudes. Moreover, the DD aerosols are transported either in the upper atmosphere or in the whole atmospheric column. This is among the first studies conducted over Athens aiming at investigating the weather conditions, pathways and transport mechanisms that favour the presence of aerosols of different characteristics. Copyright © 2011 Royal Meteorological Society