Abstract: Rapid urbanization makes urban canopy be a complex system with complex meteorological factors and energy exchange. In this study,the numerical model was used to research the matter and energy flows between building and urban local climate and reveal the physical mechanism of urban climate effect. It is of important significance to find the balance point between the thermal comfortable,energy saving and environmental protection. AUSSSM model with thermodynamics and dynamics theory was the foundation of this study. As a valley city with the distinctive topographical features,serious air pollution and significant urban heat island effect,Lanzhou City was chosen as the study area to simulate and analyze the local climatic parameters of typical building group in summer and the daily variation of air temperature in urban canopy. The profiles of air temperature and humidity ratio in different periods were simulated. The variation of temperature at the east,west,south and north metopes from the ground floor to the cockloft of building were simulated. The daily variation of surface temperature and evaporation of barer soil,asphalt,lawn and concrete roof were also simulated. The distribution of shortwave radiation in urban canopy,shortwave radiation of earth reflection,inverse long-wave radiation,ground long-wave radiation,net radiation and the effect of aerosol on radiation transfer were revealed.

Key words: urban climate, building thermal environment, coupled simulation, Lanzhou City