珠三角城市化对大气边界层特征影响的数值模拟

利用WRF/UCM模式对珠江三角洲2008年秋季一次大气污染过程的气象场特征进行模拟。在模式中针对下垫面类型数据和人为热通量来设置敏感性试验以探讨城市化对大气边界层特征的影响。研究结果表明:城市化发展(包括城市土地利用类型的改变以及人为热通量的加入和增加)均能增强城市热岛效应和干岛效应,使夜间地面逆温现象更加显著,地面污染物容易积累;地表粗糙度的增加使风速减小,城市化使热岛环流增强,污染物难以扩散,这也是造成空气污染事件的原因;同时城市的发展能抬升白天和夜晚的大气边界层高度。

Numerical Simulation of the Urbanization Impact on Atmospheric Boundary Layer Characteristics over the Pearl River Delta,China

WRF/UCM model was used to simulate the meteorological characteristics of an air pollution episode over the Pearl River Delta (PRD) in autumn, 2008. In order to study the impact of urbanization on atmospheric boundary layer characteristics, this article set up sensitivity experiments by changing the surface land use type and the anthropogenic heat flux. The results showed that urbanization, including the increase of urban area, anthropogenic heat and the increase of its flux, helped to strengthen the effect of urban heat island and urban dry island, and the surface temperature inversion turned to be more obvious, which resulted in the accumulation of surface pollutants. Urbanization not only decreased the wind speed due to the increase of surface roughness, but also strengthened the heat island circulation, which was adverse to the diffusion of pollutants and caused the pollution episodes in urban areas. Moreover, the urbanization could raise the atmospheric boundary layer height both in daytime and nighttime.