Diurnal variation and cloud in a general circulation model

Abstract

Abstract It is shown that changing the resolution of the diurnal cycle of cloud and radiative fluxes in an atmospheric general circulation model can affect the simulated climate. The effect on radiative forcing of using a temporal resolution which is unable to represent accurately the phase of diurnal variation in cloud is illustrated using a radiative‐convective version of the model. Similar results are found in the full model simulation for July, especially over land in the tropics. A detailed study of the changes over North Africa shows that the reduction in solar heating at the surface leads to a reduction in low‐level convergence and rainfall, and increased low cloud. The results indicate that cloud amounts need to be updated more frequently than four times a day if the model simulation is not to be degraded when the diurnal cycle is represented.