[1] Natl & Kapodistrian Univ Athens, Div Phys, Dept Environm Phys & Meteorol, Athens 15784, Greece
[2] Berg Univ Wuppertal, Fac Nat Sci & Math, Dept Chem, Phys Chem Lab, D-42097 Wuppertal, Germany
[3] Karlsruhe Inst Technol, Inst Meteorol & Climate Res, Atmospher Environm Res IMK IFU, D-82467 Garmisch Partenkirchen, Germany