title: Sources and Processes Affecting Fine Particulate Matter Pollution over North China: An Adjoint Analysis of the Beijing APEC Period.
abstract: The stringent emission controls during the APEC 2014 (the Asia-Pacific Economic Cooperation Summit; November 5-11, 2014) offer a unique opportunity to quantify factors affecting fine particulate matter (PM2.5) pollution over North China. Here we apply a four-dimensional variational data assimilation system using the adjoint model of GEOS-Chem to address this issue. Hourly surface measurements of PM2.5 and SO2 for October 15-November 14, 2014 are assimilated into the model to optimize daily aerosol primary and precursor emissions over North China. Measured PM2.5 concentrations in Beijing average 50.3 μg m(-3) during APEC, 43% lower than the mean concentration (88.2 μg m(-3)) for the whole period including APEC. Model results attribute about half of the reduction to meteorology due to active cold surge occurrences during APEC. Assimilation of surface measurements largely reduces the model biases and estimates 6%-30% lower aerosol emissions in the Beijing-Tianjin-Hebei region during APEC than in late October. We further demonstrate that high PM2.5 events in Beijing during this period can be occasionally contributed by natural mineral dust, but more events show large sensitivities to inorganic aerosol sources, particularly emissions of ammonia (NH3) and nitrogen oxides (NOx) reflecting strong formation of aerosol nitrate in the fall season.
authors.affiliation: Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University , Beijing 100871, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University , Beijing 100871, China.
authors.forename: Jingyuan
authors.initials: J
authors.lastname: Shao
authors.affiliation: Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University , Beijing 100871, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Lu
authors.affiliation: Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University , Beijing 100871, China.
authors.forename: Yuanhong
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University , Beijing 100871, China.
authors.forename: Yongyun
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Mechanical Engineering, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Daven K
authors.initials: DK
authors.lastname: Henze
authors.affiliation: School of Environmental Science and Engineering, Nanjing University of Information Science & Technology , Nanjing 210044, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Liao
authors.affiliation: Key Laboratory for Atmospheric Chemistry, Chinese Academy of Meteorological Sciences, CMA , Beijing, China.
authors.forename: Sunling
authors.initials: S
authors.lastname: Gong
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, Tsinghua University , Beijing 100084, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D000393:Air Pollutants; D000068476:Beijing; D002681:China; D004784:Environmental Monitoring; D052638:Particulate Matter
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter