南京城市化进程对大气边界层的影响研究

Impact of Nanjing urban development on the boundary layer

为了研究城市化进程对城市边界层结构的影响,通过高分辨率的卫星遥感资料获得土地利用类型,以及地表反照率、植被指数等地表参数,以南京为例,运用数值模拟手段进行了研究,结果显示这是一种可行的手段.数值模拟结果表明,随着城市的发展,城市反照率减小、植被减少、地表湿度减小,蒸发耗热减少,感热通量增加140 W/m2,城市波恩比增加.地表和大气之间热量交换加强,湍流热量通量增大了一倍,湍流交换发展加剧,14:00混合层高度抬高了500 m.地表湍流水汽通量和空气中水汽含量都减小,这也使更多的热量用于加热地表和大气,使地温、气温的日变化幅度增加.

In order to understand how urban development changes the local urban boundary layer structure, the data from high-resolution satellite observation have been used to get detailed information of land-use types, surface albedo, vegetation index and so on and perform regional boundary layer simulation for the case of Nanjing. It is proved that this is an effective method and these data will help to get more reasonable simulation which are close to the realities. The numerical results illustrate that with urban developing, the surface albedo decreases, the vegetation cover decreases and the surface wetness decreases, so surface sensible heat flux increases with a maximum of 140 W/m^2 , and less vegetation will lead to decrease of latent heat consumption and increase the Bowen ratio in urban areas. The kinetic heat flux will increase and the turbulence exchange will be stronger, at 14：00 the mixing layer is even lifted by a 500 m. The decreases of both kinetic moisture flux and vapor concentration cause that more energy will heat the earth surface and atmosphere, the diurnal change of earth surface temperature and atmospheric temperature will increase.