Abstract
Abstract. Using a combination of ozonesonde data and numerical simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS), the trend of tropospheric ozone (O3) during 2002–2010 over Beijing was investigated. Tropospheric ozone over Beijing shows a winter minimum and a broad summer maximum with a clear positive trend in the maximum summer ozone concentration over the last decade. The observed significant trend of tropospheric column ozone is mainly caused by photochemical production (3.1% yr−1 for a mean level of 52 DU). This trend is close to the significant trend of partial column ozone in the lower troposphere (0–3 km) resulting from the enhanced photochemical production during summer (3.0% yr−1 for a mean level of 23 DU). Analysis of the CLaMS simulation shows that transport rather than chemistry drives most of the seasonality of tropospheric ozone. However, dynamical processes alone cannot explain the trend of tropospheric ozone in the observational data. Clearly enhanced ozone values and a negative vertical ozone gradient in the lower troposphere in the observational data emphasize the importance of photochemistry within the troposphere during spring and summer, and suggest that the photochemistry within the troposphere significantly contributes to the tropospheric ozone trend over Beijing during the last decade.
Highlights
Ozone (O3) is a critical trace gas in the troposphere, playing an important role in atmospheric chemistry, air quality and climate change
If there are no observations available from the Xianghe station, we used total column ozone derived from the Ozone Monitoring Instrument (OMI), the Global Ozone Monitoring Experiment (GOME) or the Scanning Imaging Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite
The OMI daily determined total column ozone data used to calculate the correction factors (CFs) were downloaded from the NASA (National Aeronautics and Space Administration) earth data website
Summary
Ozone (O3) is a critical trace gas in the troposphere, playing an important role in atmospheric chemistry, air quality and climate change. The combined effects of these two sources and the transport processes within the troposphere control the temporal and spatial distribution of tropospheric ozone These processes render the spatial and temporal ozone variations rather complex, especially in strongly polluted regions where ozone precursors, in particular NOx (NOx = NO + NO2) and hydrocarbons (Sillman et al, 1990; Kleinman et al, 2002; Wang et al, 2006; Hogrefe et al, 2011), cause enhanced ozone concentrations during photochemically active seasons. Increasing surface ozone concentrations in the urban and background atmosphere over China, together with an enhanced spatial and temporal variability are apparent in long-term records from surface and aircraft observations (e.g., Ding et al, 2008; Xu et al, 2008; Wang et al, 2009a).
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