ON THE INFLUENCE OF THE PHYSICOCHEMICAL PROPERTIES OF AEROSOLS ON THE LIFE-CYCLE OF RADIATION FOGS

A one-dimensional model of radiation fog with detailed microphysics is presented. Aerosols and cloud droplets are treated in a joint two-dimensional size distribution. Radiative fluxes are calculated as functions of the radiative properties of the time-dependent particle spectra. The droplet growth equation is solved by considering radiative effects. Turbulence is treated by means of a higher order closure model. The interaction between the atmosphere and the earth's surface is explictly simulated. Three numerical sensitivity studies are performed to investigate the impact of the different physico-chemical properties of urban, rural and maritime aerosols on fog formation. Numerical results elucidate that depending on the aerosol type used, the resulting fog events are completely different. This is particularly true for the times of fog formation and dissipation as well for the liquid water content and supersaturations within the fogs. In the activated part of the particle spectra, the aerosol mass is very inhomogeneously distributed. The maxima of the curves do not coincide with the maxima of the corresponding liquid water distributions.