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 r adiation and surface processes is analyzed. The model used is the NCAR Regi onal Climate Model (RegCM), the period of simulation is 13 months in length , and the emphasis of the analysis is on surface climatology, monsoon circu lations, cloudiness, surface solar radiation, and top of the atmosphere out going longwave radiation. The model reproduces the basic features of the se asonal evolution of east Asia climate, but it overpredicts the intensity of the mature phase of the eastern Asia monsoon. Surface solar radiation is c omparable with observations, while outgoing longwave radiation is mostly un derestimated. Different formulations of large-scale cloud-producing mechani sms are shown to significantly affect cloud profiles, the surface and top o f the atmosphere radiation budgets, and as a consequence, the simulated sur face climatology. Variations in surface characteristics affect precipitatio n simulation in different ways during the cold/dry and warm/wet seasons. Th is paper emphasizes the importance of examining cloud radiation processes i n regional climate models in greater detail than has been done in past stud ies.