Preprints
https://doi.org/10.5194/acp-2020-727
https://doi.org/10.5194/acp-2020-727

  22 Oct 2020

22 Oct 2020

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

A study of the effect of aerosols on surface ozone through meteorology feedbacks over China

Yawei Qu1,2,3, Apostolos Voulgarakis2,4, Tijian Wang1, Matthew Kasoar2, Chris Wells2, Cheng Yuan5, Sunil Varma2, and Laura Mansfield2 Yawei Qu et al.
  • 1School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • 2Leverhulme Centre for Wildfires, Environment and Society, Department of Physics, Imperial College London, London, UK
  • 3School of Intelligent Science and Control Engineering, Jinling Institute of Technology, Nanjing, China
  • 4School of Environmental Engineering, Technical University of Crete, Crete, Greece
  • 5School of Atmospheric Physics, Nanjing University of Information Science & Technology, Nanjing, China

Abstract. Interactions between aerosols and gases in the atmosphere have been the focus of an increasing number of studies in recent years. Here, we focus on aerosol effects on tropospheric ozone that involve meteorological feedbacks induced by aerosol-radiation interactions. Specifically, we study the effects that involve aerosol influences on the transport of gaseous pollutants and on atmospheric moisture, both of which can impact ozone chemistry. For this purpose, we use the UK Earth System Model (UKESM1) with which we performed sensitivity simulations including and excluding the aerosol direct radiative effect (ADE) on atmospheric chemistry, and focused our analysis on an area with high aerosol presence, namely China. By comparing the simulations, we found that ADE reduced the shortwave radiation by 11 % in China, and consequently led to lower turbulent kinetic energy, weaker horizontal winds and a shallower boundary layer (with a maximum of 102.28 m reduction in north China). On the one hand, the suppressed boundary layer limited the export and diffusion of pollutants, and increased the concentration of CO, SO2, NO, NO2, PM2.5 and PM10 in the aerosol rich regions. The NO / NO2 ratio generally increased and led to more ozone depletion. On the other hand, the boundary layer top acted as a barrier that trapped moisture at lower altitudes and reduced the moisture at higher altitudes (the specific humidity was reduced by 1.69 % at 1493 m averaged in China). Due to reduced water vapor, fewer clouds were formed, and more sunlight reached the surface, so the photolytical production of ozone increased. Under the combined effect of the two meteorology feedback methods, the annual average ozone concentration in China declined by 2.01 ppb (6.2 %), which was found to bring the model in closer agreement with surface ozone measurements from different parts of China.

Yawei Qu et al.

 
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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Yawei Qu et al.

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Short summary
The meteorological effect of aerosols on tropospheric ozone is investigated using global atmospheric modelling. We found that aerosol-induced meteorological effects act to reduce modelled ozone concentrations over China, which brings the simulation closer to observed levels. Our work sheds light on understudied processes affecting the levels of tropospheric gaseous pollutants and provides a basis for evaluating such processes using a combination of observations and model sensitivity experiments.
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