1. Institute of Meteorology and ClimatologyLeibniz University Hannover Hannover Germany
2. Now at METEK Meteorologische Messtechnik GmbH Elmshorn Germany
3. Now at Cooperative Institute for Research in Environmental Sciences (CIRES)University of Colorado Boulder Boulder CO USA
4. Now at Chemical Sciences DivisionNOAA Earth System Research Laboratory (ESRL) Boulder CO USA