A two-dimensional (latitude-height) tropospheric tracer model has been used to simulate the global distributions of CO2, 85Kr, 222Rn, and SO2. A nondiffusive parameterization has been developed describing subgrid scale vertical transport, including transport in convective clouds and frontal zones of midlatitude cyclones. The parameters governing this transport have been estimated using the seasonal variation of CO2. For long-lived tracers such as CO2 and 85Kr the parameterization yields results that are similar to those obtained with the subgrid scale vertical transport described as an eddy diffusion process only. For short-lived tracers, with lifetimes of a few days to weeks, the nondiffusive parameterization results in vertical concentration profiles that are much steeper and probably more realistic than those obtained with a diffusive parameterization. ¿ American Geophysical Union 1990