Impact of horizontal resolution on simulation of precipitation extremes in an aqua-planet version of the Community Atmosphere Model (CAM)

Developing robust model for the projection of more frequent extreme conditions in response to global climate change has become increasingly important. One of the key questions is whether the projection of these highly localized phenomena converges as the resolution of the models increases. Evidences from the IPCC AR4 in fact suggest that the models are not convergent. A series of AGCM runs with idealized “aquaplanet-steady-state” boundary conditions have been performed with CAM3 to investigate the effect of horizontal resolution on climate extreme simulations. The results show that horizontal resolution, as well as timestep, has strong impact on the simulations of precipitation extremes. The horizontal resolution has much stronger impact on precipitation extremes compared with mean precipitation, and the dependence on resolution is primarily due to the simulation of prognostic large-scale precipitation. The horizontal resolution has little impact on simulation of temperature extremes in the current idealized model.