Experiment Alsdan (1985): Some Preliminary Results of Height Resolved Measurements of Trace Gases, Aerosol Composition, Cloud- and Precipitation Water

In- and below-cloud scavenging experiments were performed at Deuselbach (49.8°N, 7.2°E), a rural site in West Germany, in April/May and October/November 1985. Cloud water samples were collected on two platforms of a TV-tower on top of a hill (861 m and 821 m a.s.l.), while rain was sequentially sampled at 754 m, 480 m, and 430 m a.s.l. Cloud- and rainwater samples were analyzed for conductivity, major anions, cations, and H2O2. We also monitored the mixing ratios of SO2, NO, NO2, O3 in air and standard meteorological parameters at 821 m and 480 m a.s.l. At the same locations, HNO3, HC1, NH3, and aerosol were measured by discontinuous sampling. The experiments were generally limited to meteorologically simple precipitation events, like frontal rains. A preliminary analysis of the data shows that the trace substance concentrations in cloudwater at the cloud base always exceed those of rainwater by a factor of 1.5 – 4. Also within the cloud a concentration gradient is observed with higher concentrations at the cloud base. Aerosol particles (r > 0.5 µm) seem to be effectively scavenged by rain droplets, while scavenging of trace gases was barely detectable except in the case of HNO3.