城市化对北京一次极端降水过程影响的数值分析

通过敏感性试验探讨了城市化对北京2011年6月23日局地极端降水事件的影响.结果表明耦合了城市冠层模式的WRF系统能较好地模拟出强降水的局地性和突发性特征,考虑了精细下垫面分类的敏感性试验模拟降水更接近实况；下垫面城市化对地表能量平衡影响明显,对大气的热量影响除加强地表对边界层大气向上感热输送外,还会减少局地地表蒸发及大气水分供应,增加边界层高度,并对移经本地的天气系统强度及水汽输送产生较明显的影响.

Numerical Simulation for the Urbanization Effects on an Extreme Rainfall in Beijing

Based on replacing the original USGS land use data with a new urban land use dataset, the 1 km gridpoint interval WRF model and its coupling Urban Canopy Model (UCM) were used to simulate an extreme rainfall event that occurred in Beijing City on 23 June 2011. The result of the sensitivity experiment more agrees with the reality than the control experiment. Difference in surface energy balance between urban and rural areas shows that in daytime urban area absorbs more solar radiation for the area exhibits lower values of albedo. Due to the lack of vegetation in the urban, which inhibits cooling by evapotranspiration, most part of the incoming energy is partitioned into sensible heat flux to heat the urban region. The urban expansion reduces natural vegetation cover, and then it can help to decrease ground evaporation and local water vapor supply, enlarge surface sensible heat flux, deepen PBL height and enhance the mixing of water vapor. Hence it is not conducive to the occurrence of the rainfall.