Venting of gases by convective clouds

A two‐dimensional dynamic model with spectral microphysics and a spectral treatment of aerosol particle and gas scavenging (DESCAM) was used to estimate the transport of gases from the marine boundary layer to the free troposphere by a medium‐sized warm precipitating convective cloud. In the simulation, three gases were considered, covering a range of Henry's law constants: an inert tracer, SO 2 , and H 2 O 2 . SO 2 was also used as the inert tracer by artificially suppressing any interaction with the cloud drops. The horizontal and vertical fluxes, their vertical means and the transport across the cloud boundaries were studied. It was calculated that for SO 2 as an inert tracer 37 kg, for SO 2 as a scavenged gas 34 kg, and for H 2 O 2 12 kg were transported from the marine boundary layer across cloud base to the free troposphere for an estimated three‐dimensional cloud. This represents a depletion of the marine boundary layer in the vicinity of the cloud by about 60%. After about half an hour of cloud life time, however, only 75% of the SO 2 and only 30% of the H 2 O 2 transported aloft still existed in the cloudy air. These residual gases could eventually participate in a long range transport if the cloud would dissipate. The rest had been scavenged by the cloud.