Tropospheric ozone climatology over Beijing: analysis of aircraftdata from the MOZAIC program

[摘要] Ozone (O₃) profiles recorded over Beijing from 1995 to 2005 by theMeasurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC)program were analyzed to provide a first climatology of tropospheric O₃over Beijing and the North China Plains (NCPs), one of the most populated andpolluted regions in China. A pooled method was adopted in the data analysisto reduce the influence of irregular sampling frequency. The troposphericO₃ over Beijing shows a seasonal and vertical distribution typical ofmid-latitude locations in the Northern Hemisphere, but has higher daytimeconcentrations in the lower troposphere, when compared to New York City,Tokyo, and Paris at similar latitude. The tropospheric O₃ over Beijingexhibits a common summer maximum and a winter minimum, with a broad summermaximum in the middle troposphere and a narrower early summer (June) peak inthe lower troposphere. Examination of meteorological and satellite datasuggests that the lower tropospheric O₃ maximum in June is a result ofstrong photochemical production, transport of regional pollution, andpossibly also more intense burnings of biomass in Central-Eastern China.Trajectory analysis indicates that in summer the regional pollution fromthe NCPs, maybe mixed with urban plumes from Beijing, played importantroles on the high O₃ concentrations in the boundary layer, but hadlimited impact on the O₃ concentrations in the middle troposphere. Acomparison of the data recorded before and after 2000 reveals that O₃ inthe lower troposphere over Beijing had a strong positive trend (approximately2% per year from 1995 to 2005) in contrast to a flat or a decreasing trendover Tokyo, New York City, and Paris, indicating worsening photochemicalpollution in Beijing and the NCPs.

[学科分类] 大气科学