夹卷对郊外大气边界层内臭氧影响的数值模拟研究

夹卷是大气边界层与自由大气进行能量和物质交换的重要途径，对边界层动力结构及边界层内温度、水汽和各种污染物浓度有重要影响。利用化学-地表-大气-土壤(CLASS)模式定量评估了夹卷过程对远郊地区大气边界层内臭氧（O₃）浓度的影响并与大气化学反应贡献进行了对比，结合地面O₃、NO_x及边界层高度、位温和比湿等观测资料和再分析资料对CLASS模拟结果进行了定量评估。结果表明:CLASS模式能较为真实地模拟夹卷和大气光化学反应对远郊地区大气边界层臭氧浓度的影响，且当自由大气层内臭氧浓度达到一定值时，两者对边界层内臭氧峰值影响相当。数值试验结果进一步揭示，夹卷对控制氮氧化物（NO_X）和可挥发性有机物(VOC_S)排放源控制效果有重要影响，且当夹卷区内O₃跳跃值增大到一定时，可完全抵消源排放减排控制的效果。本研究旨在表明，为有效控制近地层臭氧浓度，在制定人为污染源减排措施时必须考虑自由大气层臭氧的夹卷贡献。 

NUMERICAL SIMULATION OF THE IMPACT OF ENTRAINMENT ON OZONE CONCENTRATION IN THE RURAL ATMOSPHERIC BOUNDARY LAYER

Entrainment is an important way for the exchange of heat, water and air pollutants between the atmospheric boundary layer and the free atmosphere. A zero-order model of Chemistry, Land-surface, Atmosphere, and Soil Slab (CLASS) was used to quantify the impact of entrainment influence on O₃ concentrations in the atmospheric boundary layer and compare its contribution with that of chemical reactions at a rural site. A series of observational data including O₃, NO_x, the boundary layer height, and potential temperature as well as reanalyzed data was used to evaluate the simulations. The results demonstrated that the CLASS model was able to capture the temporal variations in the atmospheric boundary layer height, surface temperature, O₃, and other chemical species. The entrainment has a competitive impact on O₃ in the PBL as compared to chemical reactions. The numerical experiments further showed that the relative contribution of entrainment increased with increasing O₃ jumps; the entrainment exerted an important impact on the control effectiveness of emission reduction of nitrogen oxides (NO_x) and volatile organic compounds (VOCs) and even totally counteracted the emission reduction effect. The study provides scientific evidence that entrainment must be considered in order to control surface O₃ concentrations effectively while the emissions were reduced.