Abstract
A parameterization scheme is described for calculating upward transport of mass in precipitating convective cells. This scheme, which is largely based on the work of Austin and Houze is implemented in a global three-dimensional tropospheric chemistry model. The convective events are stochastically distributed in time and space. The vertical exchange of mass by the clouds is derived from the conservation of water given the convective amount of precipitation and average large-scale temperature and humidity distribution. The sensitivity of the scheme is tested by varying several key parameters in the model. The ensuing vertical transport of mass is presented and compared to other approaches. A further test was made with 222Rn, a short-lived radioisotope which is largely released from land surfaces. The simulated distribution is in good agreement with measurements. The importance of convective processes for the transport of short-lived tracers is clearly demonstrated.