A European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites

Marco Pandolfi (1) , Lucas Alados-Arboledas (2) , Andres Alastuey (1) , Marcos Andrade (3) , Christo Angelov (4) , Begona Artinano (5) , John Backman (6, 7) , Urs Baltensperger (8) , Paolo Bonasoni (9) , Nicolas Bukowiecki (8) , Martine Collaud Coen (10) , Sébastien Conil (11) , Esther Coz (5) , Vincent Crenn (12, 13) , Vadimas Dudoitis (14) , Marina Ealo (1) , Kostas Eleftheriadis (15) , Olivier Favez (16) , Prodromos Fetfatzis (15) , Markus Fiebig (17) , Harald Flentje , Patrick Ginot (18) , Martin Gysel , Bas Henzing (19) , Andras Hoffer , Adela Holubova Smejkalova , Ivo Kalapov (4) , Nikos Kalivitis (20, 21) , Giorgos Kouvarakis (20) , Adam Kristensson (22) , Markku Kulmala (6) , Heikki Lihavainen (7) , Chris Lunder (17) , Krista Luoma (6) , Hassan Lyamani (2) , Angela Marinoni (9) , Nikos Mihalopoulos (20, 21) , Marcel Moerman (19) , Jose B. Nicolas (23) , Colin O’dowd , Tuukka Petaja (6) , Jean-Eudes Petit (16, 12, 24) , Jean Marc Pichon (23) , Nina Prokopciuk (14) , Jean-Philippe Putaud (25) , Sergio Rodríguez , Jean Sciare (12, 24) , Karine Sellegri (23) , Erik Swietlicki (22) , Gloria Titos (2) , Thomas Tuch (26) , Peter Tunved , Vidmantas Ulevicius (14) , Aditya Vaishya (27) , Milan Vana , Aki Virkkula (6) , Stergios Vratolis (15) , Ernest Weingartner (8) , Alfred Wiedensohler (3) , Paolo Laj (6, 9, 18)

1 IDAEA - Institute of Environmental Assessment and Water Research
2 UGR - Universidad de Granada = University of Granada
3 UMSA - Universidad Mayor de San Andrés
4 BAS - Bulgarian Academy of Sciences
5 CIEMAT - Centro de Investigaciones Energéticas Medioambientales y Tecnológicas [Madrid]
6 Helsingin yliopisto = Helsingfors universitet = University of Helsinki
7 FMI - Finnish Meteorological Institute
8 LAC - Laboratory of Atmospheric Chemistry [Paul Scherrer Institute]
9 ISAC - CNR Institute of Atmospheric Sciences and Climate
10 Federal Office of Meteorology and Climatology MeteoSwiss
11 Observatoire Pérenne de l'Environnement
12 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
13 ADDAIR Sté (France)
14 FTMC - Center for Physical Sciences and Technology [Vilnius]
15 National Centre for Scientific Research Demokritos
16 INERIS - Institut National de l'Environnement Industriel et des Risques
17 NILU - Norwegian Institute for Air Research
18 IGE - Institut des Géosciences de l’Environnement
19 TNO - The Netherlands Organisation for Applied Scientific Research
20 UOC - University of Crete [Heraklion]
21 NOA - National Observatory of Athens
22 Lund University [Lund]
23 LaMP - Laboratoire de Météorologie Physique
24 CAE - Chimie Atmosphérique Expérimentale
25 IES - JRC Institute for Environment and Sustainability
26 TROPOS - Leibniz Institute for Tropospheric Research
27 Vikram Sarabhai Space Ctr

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.

Domains: Environmental Sciences

Marco Pandolfi, Lucas Alados-Arboledas, Andres Alastuey, Marcos Andrade, Christo Angelov, et al.. A European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites. Atmospheric Chemistry and Physics, 2018, 18, pp.8727-8744. ⟨10.5194/acp-18-7877-2018⟩. ⟨ineris-01863464⟩