title: A synchronous observation of enhanced aerosol and NO2over Beijing, China, in winter 2015.
abstract: Despite extensive efforts into the characterization of air pollution during the past decade, concurrent real-time characterization of aerosol and NO2as well as satellite observation above the urban canopy in the megacity of Beijing has sparsely been performed to date. We conducted a simultaneous real-time measurement of aerosol and NO2in urban Beijing in a pollution episode from November 25, 2015 to December 2, 2015. The aerosol extinction coefficient was measured by a 532 Mie lidar and the NO2concentration by a Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). The highest aerosol extinction coefficient was 1.55 (±0.16) km-1at 532m at a height of 0.27km. The high average aerosol extinction was observed throughout the pollution period, probably due to the favorable static weather conditions under high surface high-pressure system and transportation sources. NO2showed similar temporal variations between ground level and 0.3km, whereas a much weaker diurnal evolution was found for NO2. The boundary layer structures were observed, and the relatively homogeneous mixture maintained the pollution within the layer under 0.5km. Ozone Monitoring Instrument (OMI) NO2products based on well-known DOAS trace gas fitting algorithm and WRF-Chem model further illustrated the simultaneous enhancement of NO2during the observation period. Backward trajectories suggest that long-range pollution transportation from northwest China contributes more to this pollution event.
authors.affiliation: Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
authors.forename: Zhenyi
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences，Xiamen 361021, China. Electronic address: chliu81@ustc.edu.cn.
authors.forename: Cheng
authors.initials: C
authors.lastname: Liu
authors.affiliation: Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Liu
authors.affiliation: Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
authors.forename: Tianshu
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Xu
keywords: Aerosol; Lidar; MAX-DOAS; NO(2)