CLOUDWATER CHEMISTRY IN THE SUBCOOLED DROPLET REGIME AT MOUNT-SONNBLICK (3106-M ASL, SALZBURG, AUSTRIA)

Cloudwater and wet precipitation (snow) samples were collected at Moun t Sonnblick during two field campaigns in May and November 1991. A new ly designed active cloud water samples was used. Concentrations of maj or anions, cations and carboxylic acids were determined. Cloudwater an d wet precipitation samples were generally more acidic in the warm sea son than in the cold season. Average cloudwater pH was 4.2 in May and 4.5 in November, average pH in snow was 4.4 in May and 5.1 in November . Average levels for sulfate (May: 96 mueq L-1, November: 64 mueq L-1) and nitrate (May: 27 mueq L-1, November: 32 mueq L-1) in cloudwater a t SBO (3 km altitude) were considerably lower than at high mountain si tes (0.9-2 km altitude) in the Eastern U.S.A. Cold season levels of su lfate in cloud water at SBO were as low as cloud water levels observed in Alaska. Equivalent concentrations of sulfate, nitrate and ammonium in snow precipitation were basically lower or equal compared to cloud water but showed higher concentrations and stronger acidity in both ph ases in May than in November. Cloud to snow ratios for major ions were higher in November showing a wider spread than in May. Average cloud to snow ratios for sulfate were 2.4 in May and 3.5 in November. For ni trate the ratio was 1.7 in May and 2.1 in November. The lower cloud to snow ratios for nitrate are explained by the ability of the ice phase to scavenge nitric acid. Cloud to snow ratios were similar to measure ments from the Swiss Alps and generally equal or lower than high eleva tion cloud to rain ratios from the U.S.A. Cloud to snow ratios for sul fate were used to reconstruct the mixing ratio of sublimation grown ic e phase and cloud water droplets during the riming process of the ice particles in the seeder-feeder mechanism. The mixing ratio of ice phas e and cloud droplets was estimated to be 1.4 in May and 2.5 in Novembe r. Sulfate to nitrate ratios were higher in cloud water than in snow a nd within the range of values found in North America. Generally, sulfa te was more concentrated than nitrate at an equivalent basis for both cloudwater and rainwater. Total equivalent concentrations of acetate w ere generally higher than those of formate which is in contrast to mea surements at remote high elevation sites in the U.S.A.