A European aerosol phenomenology - 6. Scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
Creators: name: Pandolfi, Marco
name: Alados-Arboledas, Lucas
name: Alastuey, Andrés
name: Andrade, Marcos
name: Angelov, Christo
name: Artiñano, Begoña
name: Backman, John
name: Baltensperger, Urs
name: Bonasoni, Paolo
name: Bukowiecki, Nicolas
name: Collaud Coen, Martine
name: Conil, Sébastien
name: Coz, Esther
name: Crenn, Vincent
name: Dudoitis, Vadimas
name: Ealo, Marina
name: Eleftheriadis, Kostas
name: Favez, Olivier
name: Fetfatzis, Prodromos
name: Fiebig, Markus
name: Flentje, Harald
name: Ginot, Patrick
name: Gysel, Martin
name: Henzing, Bas
name: Hoffer, Andras
name: Holubova Smejkalova, Adela
name: Kalapov, Ivo
name: Kalivitis, Nikos
name: Kouvarakis, Giorgos
name: Kristensson, Adam
name: Kulmala, Markku
name: Lihavainen, Heikki
name: Lunder, Chris
name: Luoma, Krista
name: Lyamani, Hassan
name: Marinoni, Angela
name: Mihalopoulos, Nikolaos
name: Moerman, Marcel
name: Nicolas, José
name: O'Dowd, Colin D.
name: Petäjä, Tuukka
name: Petit, Jean-Eudes
name: Pichon, Jean Marc
name: Prokopciuk, Nina
name: Putaud, Jean-Philippe
name: Rodríguez, Sergio
name: Sciare, Jean
name: Sellegri, Karine
name: Swietlicki, Erik
name: Titos, Gloria
name: Tuch, Thomas
name: Tunved, Peter
name: Ulevicius, Vidmantas
name: Vaishya, Aditya
name: Vana, Milan
name: Virkkula, Aki
name: Vratolis, Stergios
name: Weingartner, Ernest
name: Wiedensohler, Alfred
name: Laj, Paolo
Publisher: name: Copernicus
Year: 2018
Subjects: subject: 620 - Ingenieurwissenschaften und Maschinenbau

description: This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intra-annual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.