中文摘要：

随着城市的不断发展，城区地表反照率等下垫面物理特征和属性会发生明显的变化，进而会对城市热岛等大气环境形成影响。文中使用中国气象科学研究院开发的新一代数值天气预报模式（GRAPES），针对2004年10月北京一次重空气污染事件中的典型城市热岛过程，分别设计了两种数值试验方案：（1）对照试验，使用模式缺省的城区下垫面反照率参数，取值0．18；（2）敏感性试验，参考同期中国科学院大气物理研究所铁塔280m高度下垫面反照率观测事实，将北京区域城市类型下垫面反照率减小至0．15。通过对比两种试验方案在1km水平分辨率下的24h模拟结果，研究了城市下垫面反照率变化对北京地区城市热岛过程的影响。结果表明：（1）GRAPES模式可成功模拟此次热岛过程中城区和郊区近地面温度的日变化趋势；（2）城市下垫面反照率的变化对城市热岛的发展非常重要，城市反照牢下降0．03会使城市热岛强度增强0．8℃左右，结果也更接近实况。这说明随着城市发展引起的地表反照率减小有利于城市热岛强度增加；（3）通过分析地表的长波辐射发现，在城市区域较小反照率情形下，城区的长波辐射始终比郊区大，有利于热岛的形成；同时也有利于城区近地层的风场辐合增加，对此次污染过程的发展是有利的。

英文摘要：

With the rapid development and expansion of city, the physical characteristics（such as surface albedo and so on）and property of the urban underlying surfaceare undergoing substantially changes, which significantly impact the atmosphere and environment, for example urban heat island （UHI） effect. By utilizing the new-generation numerical GRAPES-meso model developed by Chinese Academy of Meteorological Science, two 24 hours numerical experiment schemes were designed and performed to investigate the impact of urban albedo change on a typical UHI event over the 13eijing metropolitan area during a serious air pollution process on 6 - 8, October 2004. The control experiment was numerically integrated with the default model albedo value of 0.18 for the urban landuse, but the sensitive experiment was conducted with a smaller urban albedo value of 0.15, which is based on the actual value observed at the 280 m high iron tower of Institute of Atmospheric Physics, Chinese Academy of Science. After comparing the results of the two numerical experiments with 1-kin fine horizontal resolution, the following major conclusions are summarized ： Either in urban area or rural area, the diurnal variation of nearsurface atmospheric temperature is successful simulated for the selected UHI event （6- 8 October 2004） by the GRAPES-meso model. The change in urban albedo has significant impact on the evolution of UHI, and a reduction of 0.03 in urban albedo would increase the intensity of UHI by about 0.8 ℃, thus yielding a more reasonable intensity of UHI relative to the actually observed value. This indicates that the reduction in urban albedio resulted from urban expansion is favor to the enhancement of UHI. In addition, under the condition of a reduced albedo for urban landuse, the long wave radiation flux is larger in urban center than that in the surrounding suburban areas, which further contributes to the development of UHI. More over, the simulated near-surface wind fields also suggest that the decrease in urban albed