Cloud Chemistry Monitoring at Mt. Brocken, Germany - 2005

The liquid water content of clouds (LWC) has been continuously measured using forward scattering of laser beams by cloud droplets with a Particulate Volume Monitor PVM-100 (Gerber Scientific Inc.). This instrument was also used to control an automated „wet-only” sampling unit that opens up and moves a passive string collector (ASRC type) into sampling position when the LWC level exceeds a 25mg/m**3 threshold. The samples were analysed by ion chromatography (DIONEX suppressor, SYKAM pump and conductivity detector, JASCO sampler) for anions ([Cl]-, [NO3]-, [SO4]2-) and cations ([Na]+, [NH4]+, [K]+, [Ca]2+, [Mg]2+), pH and conductivity. The acceptance criteria for ion balance and for conductivity (measured/calculated), respectively, are defined in the Reports 85 (1992) and 102 (1994) of the WMO for all activities within the GAW program and also we did follow rigorously these standard practices. The whole measurement and analytical procedure was laid down in standard operating procedures. […]