VERTICAL TRANSPORT OF TRACE SPECIES BY THUNDERSTORMS - A TRANSILIENT TRANSPORT MODEL

A 2D-cloud model with spectral microphysics including ice physics and aerosol particle scavenging effects is used to simulate the 19 July 1981 CCOPE thunderstorm case. The net vertical transport of a chemically inert tracer between 30 respective levels by a single thunderstorm was determined in terms of a transilient matrix. Additionally, the redistribution of sulfur which was assumed to be initially present in aerosol particles was investigated. Beside transport with the mean wind, nucleation scavenging, particle scavenging, and wet deposition contribute to the observed redistribution. - The simulations show that even a moderate thunderstorm may reduce the pollution in the boundary layer by 50%. Trace species may be transported in less than half an hour from the ground to the upper troposphere and, in contrast, trace species originating from the upper troposphere may not have the change to be transported down to the ground. Net mixing strongly depends on the detailed dynamical and microphysical structure of the investigated thunderstorm. The hypothesis that thunderstorms play an important role in redistribution and wet deposition of airborne aerosol article mass is confirmed.