关键词: 绿化, 城市边界层结构, 数值模拟, 地表通量

Abstract: The impact of afforestation in the mountains in the north and south of Lanzhou city on urban boundary layer structure in winter is simulated by using RAMS(Regional Atmospheric Modeling System). The numerical simulation results show that afforestation changes the temperature and wind fields in the surface layer. In terms of daily mean temperature field, afforestation exhibits an obviously heating effect to Lanzhou city. According to the wind field, the anabatic wind was strengthened over the south mountains at 14:00 BT(Beijing Time). However, the katabatic wind was strengthened over the north mountains at 02:00 BT. With regard to the energy budget in the winter, the amount of net solar radiation and sensible heat flux is higher on afforestated soil than that on bare soil in permafrost area in winter. The increase of forests can increase the turbulent energy in daytime, and this impact could be transported to the upper atmosphere and results in a weaker elevated temperature inversion. The effect of different greenbelts on the elevated temperature inversion in daytime is also discussed in this paper.

Key words: afforestation, urban boundary layer structure, numerical simulation, surface energy budget