Worsening urban ozone pollution in China from 2013 to 2017 - Part 1: The complex and varying roles of meteorology

Yiming Liu, Tao Wang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

44 Citations (Scopus)

Abstract

China has suffered from increasing levels of ozone pollution in urban areas despite the implementation of various stringent emission reduction measures since 2013. In this study, we conducted numerical experiments with an up-to-date regional chemical transport model to assess the contribution of the changes in meteorological conditions and anthropogenic emissions to the summer ozone level from 2013 to 2017 in various regions of China. The model can faithfully reproduce the observed meteorological parameters and air pollutant concentrations and capture the increasing trend in the surface maximum daily 8&thinsp;<span classCombining double low line"inline-formula">h</span> average (MDA8) ozone (<span classCombining double low line"inline-formula">O3</span>) from 2013 to 2017. The emission-control measures implemented by the government induced a decrease in MDA8 <span classCombining double low line"inline-formula">O3</span> levels in rural areas but an increase in urban areas. The meteorological influence on the ozone trend varied by region and by year and could be comparable to or even more significant than the impact of changes in anthropogenic emissions. Meteorological conditions can modulate the ozone concentration via direct (e.g., increasing reaction rates at higher temperatures) and indirect (e.g., increasing biogenic emissions at higher temperatures) effects. As an essential source of volatile organic compounds that contributes to ozone formation, the variation in biogenic emissions during summer varied across regions and was mainly affected by temperature. China's midlatitude areas (25 to 40<span classCombining double low line"inline-formula">ĝ&circ; </span>&thinsp;N) experienced a significant decrease in MDA8 <span classCombining double low line"inline-formula">O3</span> due to a decline in biogenic emissions, especially for the Yangtze River Delta and Sichuan Basin regions in 2014 and 2015. In contrast, in northern (north of 40<span classCombining double low line"inline-formula">ĝ&circ; </span>&thinsp;N) and southern (south of 25<span classCombining double low line"inline-formula">ĝ&circ; </span>&thinsp;N) China, higher temperatures after 2013 led to an increase in MDA8 <span classCombining double low line"inline-formula">O3</span> via an increase in biogenic emissions. We also assessed the individual effects of changes in temperature, specific humidity, wind field, planetary boundary layer height, clouds, and precipitation on ozone levels from 2013 to 2017. The results show that the wind field change made a significant contribution to the increase in surface ozone over many parts of China. The long-range transport of ozone and its precursors from outside the modeling domain also contributed to the increase in MDA8 <span classCombining double low line"inline-formula">O3</span> in China, especially on the Qinghai-Tibetan Plateau (an increase of 1 to 4&thinsp;ppbv). Our study represents the most comprehensive and up-to-date analysis of the impact of changes in meteorology on ozone across China and highlights the importance of considering meteorological variations when assessing the effectiveness of emission control on changes in the ozone levels in recent years.

Original languageEnglish
Pages (from-to)6305-6321
Number of pages17
JournalAtmospheric Chemistry and Physics
Volume20
Issue number11
DOIs
Publication statusPublished - 3 Jun 2020

ASJC Scopus subject areas

  • Atmospheric Science

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