A European aerosol phenomenology-5: Climatology of black carbon optical properties at 9 regional background sites across Europe

M. Zanatta, M. Gysel, N. Bukowiecki, T. Müller, E. Weingartner, H. Areskoug, Markus Fiebig, Karl Espen Yttri, N. Mihalopoulos, G. Kouvarakis, D. Beddows, R.M. Harrison, F. Cavalli, J.P. Putaud, G. Spindler, A. Wiedensohler, A. Alastuey, M. Pandolfi, K. Sellegri, E. Swietlicki, J.L. Jaffrezo, U. Baltensperger, P. Laj