[1] Netherlands Energy Research Foundation (ECN), Petten, 1755 ZG
[2] Zentrum für Umweltforschung, Johann Wolfgang Goethe University, Frankfurt, 6000
[3] Department of Meteorology and Geophysics, Johann Wolfgang Goethe University, Frankfurt, 6000
[4] Department of Meteorology, University of Stockholm, Stockholm
[5] Istituto FISBAT C.N.R, Bologna, 40126
[6] Meteorological Observatory Hamburg, Hamburg, 2000