Deep cumulus convection (DCC) plays an important role in the hydrological cycle of the climate system, the dynamics of the atmospheric circulation and the transport of trace gases within the troposphere. A major source of uncertainty in climate models is associated with the representation of cumulus convection. DCC also affects atmospheric chemistry indirectly through latent heating and contributions to the budgets of solar and infrared radiation.
A modified cumulus convection parametrisation scheme is presented in this paper. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset.
The simulated convective precipitation rate and mass fluxes are compared with observations and reanalysis data. A simulation of the short-lived tracer 222Rn is used to further evaluate the performance of the cumulus convection scheme. Simulated distributions of 222Rn are evaluated against observations at the surface and in the free troposphere. They are then compared with output from models that participated in the TransCom-CH4 Transport Model Intercomparison, including two different simulations using the LLNL IMPACT model at moderate and then at high resolution. From this comparison, it is demonstrated that the proposed convective scheme is generally consistent with observed and modeled results.