Summertime fog chemistry at a mountainous site in central Europe

In this paper, 1997 atmospheric visibility data as an indicator for the presence and density of fog at our ecosystem research site in the Fichtelgebirge mountains, Central Europe, are presented. At this location (about 800 m a.s.l.), fog occurred on 50% of the days and added up to a total fog duration of 1158 h in 1997. Using the visibility as a determining parameter, an automatic system for the collection of fog water was developed, including an automatic sampler, and sampling on an event basis. The data from the summer 1997 season exhibit a large variability in the chemical composition of fog. Easterly winds were associated with fog with higher concentrations of the major ions (NH4+, NO3−, SO42−) and metals than westerly winds. Although the H+ concentrations are lower than concentrations measured between 1983 and 1988 in NE Bavaria, it is not clear from our data alone if the negative trend over time is significant. A simple parameterization of fog deposition shows that fog plays an important role in the water balance of our forests. However, more detailed studies are needed to quantify this input, and the input of pollutants and nutrients to the ecosystems through fog deposition.