The effect of horizontal resolution of the simulation of precipitation extremes in the Community Atmospheric model version 5.1

Contemporary high performance computing technology currently enables multi-decadal global atmospheric models at horizontal resolutions of 25km. Simulated storms in such models exhibit sharper gradients and higher extreme precipitations rates than is typical in CMIP5 class models. We compare daily and pentad extreme precipitation statistics from the Community Atmospheric model version 5.1 (CAM5.1) at resolutions of approximately 200, 100 and 25km at the equator with available gridded observational products. We find that there is considerable observational uncertainty in these products, but that the high-resolution configuration performs better than low-resolution configurations when cumulus processes do not contribute significantly to precipitation rates. However, we also find no evidence that simulated extreme precipitation rates have converged at the 25km resolution.