1. Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland, Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland, Australian National University, ACT 0200, Australia, Institute for Water and Environmental Problems, 656099 Barnaul, Russia, Texas A&M University, Galveston, Texas 77551, and Division of Climate and Environmental Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland