Finnish Meteorological Institute, P.O.Box 503, Helsinki, FIN-00101, Finland; University of Michigan, Departmen of Atmospheric, Oceanic and Space Sciences, 2455 Hayward St., Ann Arbor, MI 48109-2143, USA
University of Michigan, Departmen of Atmospheric, Oceanic and Space Sciences, 2455 Hayward St., Ann Arbor, MI 48109-2143, USA
University of S.-Petersburg, Institute of Physics, Petrodvorets, Ulyanovskaya, 1, St.- Petersburg, 198504, Russian Federation