title: Origin of non-spherical particles in the boundary layer over Beijing, China: based on balloon-borne observations.
abstract: Vertical structures of aerosols from the ground to about 1,000 m altitude in Beijing were measured with a balloon-borne optical particle counter. The results showed that, in hazy days, there were inversions at approximately 500-600 m, below which the particulate matters were well mixed vertically, while the concentration of particles decreased sharply above the mixing layer. Electron microscopic observation of the particles collected with the balloon-borne impactor indicates that the composition of particles is different according to weather conditions in the boundary mixing layer of Beijing city and suggests that dust particles are always dominant in coarse-mode particles. Interestingly, sea-salt particles are frequently identified, suggesting the importance of marine air inflow to the Beijing area even in summer. The Ca-rich spherical particles are also frequently identified, suggesting chemical modification of dust particle by NOx or emission of CaO and others from local emission. Additionally, those types of particles showed higher concentration above the mixing layer under the relatively calm weather condition of summer, suggesting the importance of local-scale convection found in summer which rapidly transported anthropogenic particles above the mixing layer. Lidar extinction profiles qualitatively have good consistency with the balloon-borne measurements. Attenuation effects of laser pulse intensity are frequently observed due to high concentration of particulate matter in the Beijing atmosphere, and therefore quantitative agreement of lidar return and aerosol concentration can be hardly observed during dusty condition. Comparing the depolarization ratio obtained from the lidar measurements with the balloon-borne measurements, the contribution of the dry sea-salt particles, in addition to the dust particles, is suggested as an important factor causing depolarization ratio in the Beijing atmosphere.
authors.affiliation: Key Laboratory of Atmospheric Composition and Optical Radiation, Chinese Academy of Sciences, Beijing, China. chen_bin@mail.iap.ac.cn.|Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China. chen_bin@mail.iap.ac.cn.
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.affiliation: Center for Innovation, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
authors.forename: Maromu
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Center for Innovation, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Iwasaka
authors.affiliation: Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, 3-1-100 Tsukide, Kumamoto, 862-8502, Japan.
authors.forename: Daizhou
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Chinese Academy of Meteorological Sciences (CAMS), Beijing, 100081, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Key Laboratory of Atmospheric Composition and Optical Radiation, Chinese Academy of Sciences, Beijing, China. zzwang@aiofm.ac.cn.
authors.forename: Zhenzhu
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China.
authors.forename: Hengchi
authors.initials: H
authors.lastname: Lei
authors.affiliation: Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Shi
mesh_terms: D000392:Air Movements; D000068476:Beijing; D004391:Dust / Q000032:analysis*; D004784:Environmental Monitoring; D008855:Microscopy, Electron, Scanning; D052638:Particulate Matter / Q000737:chemistry*; D012621:Seasons; D013052:Spectrometry, X-Ray Emission; D014887:Weather
chemical_list: D004391:Dust; D052638:Particulate Matter
keywords: Aerosol; Beijing; Boundary layer; Tethered balloon; Vertical mixing