title: Analysis of the origin of peak aerosol optical depth in springtime over the Gulf of Tonkin.
abstract: By aggregating MODIS (moderate-resolution imaging spectroradiometer) AOD (aerosol optical depth) and OMI (ozone monitoring instrument) UVAI (ultra violet aerosol index) datasets over 2010-2014, it was found that peak aerosol loading in seasonal variation occurred annually in spring over the Gulf of Tonkin (17-23 °N, 105-110 °E). The vertical structure of the aerosol extinction coefficient retrieved from the spaceborne lidar CALIOP (cloud-aerosol lidar with orthogonal polarization) showed that the springtime peak AOD could be attributed to an abrupt increase in aerosol loading between altitudes of 2 and 5 km. In contrast, aerosol loading in the low atmosphere (below 1 km) was only half of that in winter. Wind fields in the low and high atmosphere exhibited opposite transportation patterns in spring over the Gulf of Tonkin, implying different sources for each level. By comparing the emission inventory of anthropogenic sources with biomass burning, and analyzing the seasonal variation of the vertical structure of aerosols over the Northern Indo-China Peninsula (NIC), it was concluded that biomass burning emissions contributed to high aerosol loading in spring. The relatively high topography and the high surface temperature in spring made planetary boundary layer height greater than 3 km over NIC. In addition, small-scale cumulus convection frequently occurred, facilitating pollutant rising to over 3 km, which was a height favoring long-range transport. Thus, pollutants emitted from biomass burning over NIC in spring were raised to the high atmosphere, then experienced long-range transport, leading to the increase in aerosol loading at high altitudes over the Gulf of Tonkin during spring.
authors.affiliation: College of Resources and Environment, Shandong Agricultural University, Taian 271000, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. Electronic address: sxlgis@foxmail.com.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Shan
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. Electronic address: xujun@craes.org.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.affiliation: College of Resources and Environment, Shandong Agricultural University, Taian 271000, China.
authors.forename: Yixue
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Han
authors.affiliation: College of Geography and Environment, Shandong Normal University, Jinan 250014, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Du
authors.affiliation: Environmental Protection Research Institute of Guangxi, Nanning 530022, China.
authors.forename: Jingying
authors.initials: J
authors.lastname: Mao
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Youjiang
authors.initials: Y
authors.lastname: He
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Xuezhi
authors.initials: X
authors.lastname: Dai
mesh_terms: D000336:Aerosols / Q000032:analysis* / Q000737:chemistry; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis*; D000531:Altitude; D001272:Atmosphere / Q000737:chemistry; D056804:Biofuels; D018533:Biomass; D002681:China; D002980:Climate; D004784:Environmental Monitoring / Q000379:methods; D010126:Ozone / Q000032:analysis; D063809:Satellite Imagery; D012621:Seasons; D014919:Wind
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D056804:Biofuels; D010126:Ozone
keywords: Aerosol optical depth; Aerosol vertical structure; Biomass burning; Gulf of Tonkin; Transportation