Abstract:The characteristics of atmospheric physical environment in urban areas are to a large extent determined by the status of underlying surface. An increase in the urban natural surface such as wetlands may help decrease surface temperature, increase humidity, change local flow field, and improve local micrometeorological conditions and atmosphere physical environment. The multi scale numerical modeling system provides an effective method for assessing quantitatively the atmospheric physical environment in urban planning. In this paper an Urban Scale Model in the system is used to simulate the variability of surface air temperature, humidity, wind velocity, atmospheric diffusion conditions and their effect on urban atmospheric environment on condition of the dispersed or converged water layout with the proportion of urban water area in urban area being 4%, 8%, 12% and 16%, respectively. Based on meteorological observation data at urban water body sites in Beijing, the differences of air temperature and humidity among the area surrounding water body, commercial areas and traffic zones are analyzed and the simulated results are compared. The results reveal that the layout of urban water body has an obvious effect on urban micrometeorological environment. No matter whether the layout is dispersed or converged, the increase of urban water body area to a certain extent leads to the decrease of surface air temperature, increase of humidity, and enlargement of wind velocity. But water body in the dispersed distribution has a more significant effect on the urban micrometeorological environment than that in the converged distribution.