Evolution of atmospheric boundary layer structure and its relationship with air quality in Wuhan, China

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Date

2017-09

Journal Title

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Publisher

Springer

Abstract

Airpollutiondata,airqualityindex(AQI)dataandLband sounding data of Wuhan City from January 1 to February 28, 2015, were used in this study. Since air quality is mainly determined by the condition of the atmospheric boundary layer structure (ABLS), a detailed analysis was carried out in order to determinethe evolutionof thislayer anditsrelationship withair quality.Duringtheinvestigationperiod,thehighestvalueofAQI was 307 on January 26 and the lowest was 33 on February 28 indicating ‘severe pollution’ and ‘excellent’ air quality, respectively. The concentrations of PM2.5 during the days with the highest and lowest AQI were 142.61 and 9.78 μg/m3, respectively. The percentage of days in which the ratio of PM2.5 in PM10 was more than half was 83.05% which means that the greaterportionofpollutantswerecomposedofsmallerparticles. Moreover, four PM2.5 episodes (three or more consecutive days ofPM2.5≥75μg/m3)wereidentifiedandtheaveragepercentage of elementary carbon (EC) in PM2.5 during episode 1 (prior to the episode) was 6.274% (6.276%), episode 2 was 5.634% (7.174%),andepisode4was4.067%(7.785%).Higherconcentrations of EC prior to episodes suggest biomass burning to be one of the reasons for episodes occurrence. Analysis of the ABLS during polluted days show that the boundary layer was dry and warm and had weak low-level wind and dominance of northerlywinds.Adifferentscenarioisseenoncleandaysasthe boundary layer is observed to be wet and cool, and there is dominance of strong winds. Back trajectory analysis results show that polluted days were dominatedbyair mass from north China while on clean days, the dominant air masses were from East China Sea, Mongolia, and west China

Description

Arab journal of Geoscience, 2017; 10: 477

Keywords

Airpollution, Airquality, Atmosphericboundary layerstructure, Episode

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