Abstract
Abstract. Within the frame of the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Météo-France aircraft ATR-42 performed 22 research flights over central Europe and the North Sea during the intensive observation period in May 2008. For the campaign, the ATR-42 was equipped to study the aerosol physical, chemical, hygroscopic and optical properties, as well as cloud microphysics. For the 22 research flights, retroplume analyses along the flight tracks were performed with FLEXPART in order to classify air masses into five sectors of origin, allowing for a qualitative evaluation of emission influence on the respective air parcel. This study shows that the extensive aerosol parameters (aerosol mass and number concentrations) show vertical decreasing gradients and in some air masses maximum mass concentrations (mainly organics) in an intermediate layer (1–3 km). The observed mass concentrations (in the boundary layer (BL): between 10 and 30 μg m−3; lower free troposphere (LFT): 0.8 and 14 μg m−3) are high especially in comparison with the 2015 European norms for PM2.5 (25 μg m−3) and with previous airborne studies performed over England (Morgan et al., 2009; McMeeking et al., 2012). Particle number size distributions show a larger fraction of particles in the accumulation size range in the LFT compared to BL. The chemical composition of submicron aerosol particles is dominated by organics in the BL, while ammonium sulphate dominates the submicron aerosols in the LFT, especially in the aerosol particles originated from north-eastern Europe (~ 80%), also experiencing nucleation events along the transport. As a consequence, first the particle CCN acting ability, shown by the CCN/CN ratio, and second the average values of the scattering cross sections of optically active particles (i.e. scattering coefficient divided by the optical active particle concentration) are increased in the LFT compared to BL.
Highlights
Hydrology and Earth SystemAerosols are known to have siSgncifiiecanntciemspact on the regional and global climate via interaction with the solar and terrestrial radiation, thereby modifying the planetary albedo and the outgoing longwave radiation (IPCC, 2007)
This study shows that the extensive aerosol parameters show vertical decreasing gradients and in some air masses maximum mass concentrations in an intermediate layer (1–3 km)
Measurements of aerosol properties performed at ground sites are numerous, facilitating model comparisons at the surface, while in situ column measurements of aerosol properties are sparse (Petzold et al, 2002; Morgan et al, 2009, 2010). These results constitute one of the few studies presenting observations over Europe of the simultaneous aerosol measurements of physical, chemical, optical and hygroscopic properties performed on board the ATR-42 in the boundary layer (BL) as well as in the lower free troposphere (LFT)
Summary
Aerosols are known to have siSgncifiiecanntciemspact on the regional and global climate via interaction with the solar and terrestrial radiation, thereby modifying the planetary albedo and the outgoing longwave radiation (IPCC, 2007). During long-range transport, aerosol particles may influence the climate by interfering directly with atmospheric radiative processes (Haywood et al, 2003; IPCC, 2007) and indirectly by modifying the distribution anSd pohlyidsicEal aprrotpherties of clouds (Lohmann et al, 2004) All these direct and indirect effects depend on aerosol particle properties : particle number. During the campaign a variety of clean marine and polluted continental air masses were encountered, and some of the key aerosol properties associated with these particular air masses are documented and reported here Distinct layers, such as the boundary layer and the lower free troposphere, could be sampled during the same flight and over different surface types (land/sea). The results of that kind of investigation are likely to be of significant interest to both the process-modelling community and the large-scale modelling community
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