Fog deposition fluxes of water and ions to a mountainous site in Central Europe

Klemm O, Wrzesinsky T

Abstract

Fog and precipitation composition and deposition were measured over a 1-yr period. Ion concentrations were higher in fog than in precipitation by factors of between 6 and 18. The causes of these differences were less dilution of fog water due to non-availability of condensable water vapour, and more efficient transfer of surface emissions to fog water as compared to rain water or snow. Fogwater and dissolved ions depositions were measured with eddy covariance in combination with a bulk fogwater collector. Annual fogwater deposition was 9.4% that of precipitation. The annual deposition of ions through fog was of the same order as that for precipitation. Ammonium, representing local emission sources, had 46% more annual deposition through fog than through precipitation. The fog droplet number and mass size distributions are reported. Fog droplets of 15 mu m diameter contribute most to the deposition flux. The variability of processes and parameters contributing to deposition of ions through fog (ion concentrations in fog water, liquid water content in air, fog duration and turbulence) is high.