Abstract
Abstract. Tropospheric ozone is both a major pollutant and a short-lived greenhouse gas and has therefore caused much concern in recent years. The ozone profile in the troposphere and lower stratosphere over Beijing has been observed since 2002 by ozonesondes developed by the Institute of Atmospheric Physics. Increasing concentrations of tropospheric ozone from 2002 to 2010 measured by these balloon-based observations have been reported previously. As more observations are now available, we used these data to analyse the long-term variability of ozone over Beijing during the whole period from 2002 to 2018. The ozonesondes measured increasing concentrations of ozone from 2002 to 2012 in both the troposphere and lower stratosphere. There was a sudden decrease in observed ozone between 2011 and 2012. After this decrease, the increasing trend in ozone concentrations slowed down, especially in the mid-troposphere, where the positive trend became neutral. We used the Chemical Lagrangian Model of the Stratosphere (CLaMS) to determine the influence of the transport of ozone from the stratosphere to the troposphere on the observed ozone profiles. CLaMS showed a weak increase in the contribution of stratospheric ozone before the decrease in 2011–2012 and a much more pronounced decrease after this time. Because there is no tropospheric chemistry in CLaMS, the sudden decrease simulated by CLaMS indicates that a smaller downward transport of ozone from the stratosphere after 2012 may explain a significant part of the observed decrease in ozone in the mid-troposphere and lower stratosphere. However, the influence of stratospheric ozone in the lower troposphere is negligible in CLaMS, and the hiatus in the positive trend after 2012 can be attributed to a reduction in ozone precursors as a result of stronger pollution control measures in Beijing.
Highlights
Tropospheric ozone is an important pollutant and is detrimental to both human health (WHO, 2006) and the productivity of vegetation (Ainsworth et al, 2012; Emberson et al, 2013; Feng et al, 2015)
Wang et al (2012) found a positive ozone trend during the time period 2002–2010. We extended these data to 2018 and found that the evolution of this trend after 2010 was strongly determined by two factors: (1) a sudden decrease in mainly stratospheric ozone from late 2011 to early 2012 and (2) a decrease in mainly tropospheric ozone caused by a reduction in air pollution in the Beijing region
We show the reduction in tropospheric NO2 by using Ozone Monitoring Instrument (OMI) measurements
Summary
Tropospheric ozone is an important pollutant and is detrimental to both human health (WHO, 2006) and the productivity of vegetation (Ainsworth et al, 2012; Emberson et al, 2013; Feng et al, 2015). Using the Infrared Atmospheric Sounding Interferometer (IASI) on board the European Space Agency’s (ESA) MetOp series of polar orbiting satellites, together with surface and ozonesonde measurements, Dufour et al (2018) reported the trend in tropospheric ozone concentrations over the North China Plain for the time period 2008–2016. They found that there were two distinct periods: (1) 2008–2012 with no significant trend and (2) 2013–2016 with a significant negative trend in lower tropospheric ozone. We used the whole time series (2002–2018) of ozonesonde observations to explore the variability in ozone concentrations over Beijing in the last 2 decades
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