b center for excellence in regional Atmospheric environment, institute of Urban environment, chinese Academy of sciences, Xiamen, china; c college of earth science, University of the chinese Academy of sciences, Beijing, china; d chinese Academy of meteorological sciences, Beijing, china ABSTRACT A field experiment of nocturnal mountain wind and corresponding particulate matter (PM) evolution under weak synoptic forcing at five sites within urban Beijing was conducted using a moving Doppler wind lidar and a fixed tower. Clear wind shear and zero-horizontal-wind zones at 40-320 m above the ground with a delay of 1.5 h were found at two sites between 20 km from north to south urban Beijing. The wind speed and height of the low-level jet at the north urban Beijing site were greater than those at the east urban Beijing site. The average horizontal distribution of low-level PM at 240 m was similar to the ground-level PM at night. The PM 2.5 (aerodynamic diameter ≤2.5 μm) accumulation center showed no abrupt changes with a shift in wind direction until the northerly wind jet arrived.摘要 临山城市夜间山风可影响污染物的分布,但夜间低层山风的演变及其对污染物分布的影响观 测研究较少。本文通过325 m气象塔及一台测风激光雷达快速移动到四地的定点观测,获取了 北京城区一次三维夜间山风及污染物分布特征,为城市测风提供了一种新方法。结果表明: 相距20 km南、北城均有低层风向切变且间隔为1.5 h;城北低空急流的高度及风速均大于城东 南;240 m和地面颗粒物的水平分布一致;PM 2.5 地面高值区的南移时间与北风急流到达时间一 致,晚于地面风转向时间。