Aerosol decadal trends - Part 1: In-situ optical measurements at GAW and IMPROVE stations

M. Collaud Coen, E. Andrews, A. Asmi, U Baltensperger, N. Bukowiecki, D. Day, Markus Fiebig, Ann Mari Fjæraa, H. Flentje, A. Hyvärinen, A Jefferson, S.G. Jennings, G. Kouvarakis, H. Lihavainen, Cathrine Lund Myhre, W. C. Malm, N. Mihapopoulos, J. V. Molenar, C O'Dowd, J.A. Ogren, B. A. Schichtel, P. Sheridan, A. Virkkula, E. Weingartner, R. Weller, P. Laj