山谷城市地形特殊，对该地形气溶胶理化特征进行观测和研究，是深入认识其气候、环境和健康效应的前提，对山谷地形气溶胶源解析和空气质量研究具有重要的科学意义。目前对山谷城市边界层逆温对气溶胶理化特征变化的响应机制还缺乏充分的认识，限制了数值模式对山谷城市天气和空气质量预报的准确性。本项目通过对兰州山谷城区气溶胶谱分布和化学成分的观测，探究大气污染减轻过程中气溶胶理化特征的演变，结合完全在线耦合模式WRF-Chem和大气边界层结构特征的观测，模拟研究不同污染程度下气溶胶理化特征的变化对冬季边界层逆温的影响，加深对典型山谷城市气溶胶与边界层逆温之间反馈机制的认识。本项目的实施对认识气溶胶物理、化学特征在山谷地形边界层逆温形成和发展中的作用，改进空气质量模式在山谷城市的模拟能力，提高空气质量预报的准确率有重要的意义。预期成果不仅为山谷城市大气污染防治提供科学依据，而且为华北平原治理雾霾污染提供科学参考。

The measurements and studies of physical and chemical characteristics of aerosols in a typical valley-shaped city are essential to deeply understand climate, environmental and health effects of aerosols, which is also conducive to studying source apportionment of aerosols and air quality over a complex terrain. Presently, responses of temperature inversion of atmospheric boundary layer (ABL) in a valley city to variations of aerosol physical and chemical characteristics are still unclear, which limits accuracy of numerical weather and air quality predictions in a typical valley-shaped city. Bases on the measurements of number size distributions and chemical composition of aerosols in urban Lanzhou, the variations of aerosol physical and chemical characteristics will be analyzed during the transitional period from the most-polluted to the less-polluted city. Combined with the characteristics of atmospheric boundary layer structure, the impacts of variations of aerosol physical and chemical properties for varying air pollution level on temperature inversion in winter will be studied by fully online coupled model of WRF-Chem, which will help to better understand the feedback between aerosol and temperature inversion over a typical valley-shaped city. The project will contribute to know the roles of aerosol physical and chemical characteristics in formation and development of ABL temperature inversion and improve simulation ability of air quality model in typical valley-shaped city. The expected results not only will provide scientific basis to air pollution prevention and control of valley-shaped city, but also will provide some scientific references for treatments of severe haze pollution of North China Plain.