A seasonal cycle simulation over eastern Asia and its sensitivity to radiative transfer and surface processes

A multiseasonal simulation over eastern Asia and its sensitivity to cloud radiation and surface processes is analyzed. The model used is the NCAR Regional Climate Model (RegCM), the period of simulation is 13 months in length, and the emphasis of the analysis is on surface climatology, monsoon circulations, cloudiness, surface solar radiation, and top of the atmosphere outgoing longwave radiation. The model reproduces the basic features of the seasonal evolution of east Asia climate, but it overpredicts the intensity of the mature phase of the eastern Asia monsoon. Surface solar radiation is comparable with observations, while outgoing longwave radiation is mostly underestimated. Different formulations of large-scale cloud-producing mechanisms are shown to significantly affect cloud profiles, the surface and top of the atmosphere radiation budgets, and as a consequence, the simulated surface climatology. Variations in surface characteristics affect precipitation simulation in different ways during the cold/dry and warm/wet seasons. This paper emphasizes the importance of examining cloud radiation processes in regional climate models in greater detail than has been done in past studies.