Preprints
https://doi.org/10.5194/acp-2022-290
https://doi.org/10.5194/acp-2022-290
 
24 May 2022
24 May 2022
Status: this preprint is currently under review for the journal ACP.

Impact of a subtropical high and a typhoon on a severe ozone pollution episode in the Pearl River Delta, China

Shanshan Ouyang1,2, Tao Deng2, Run Liu1,3, Jingyang Chen4, Guowen He2,5, Jeremy Cheuk-Hin Leung2, Nan Wang2, and Shaw Chen Liu1,3 Shanshan Ouyang et al.
  • 1Institute for Environmental and Climate Research, Jinan University, Guangzhou, 511443, China
  • 2Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction, China Meteorological Administration, Guangzhou 510640, China
  • 3Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou, 511443, China
  • 4Guangdong Ecological Meteorology Center (Pearl River Delta Center for Environmental Meteorology Prediction and Warning), Guangzhou 510640, China
  • 5School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China

Abstract. A record-breaking severe ozone (O3) pollution episode occurred in the Pearl River Delta (PRD) in early Autumn 2019 when PRD was under the influence of a Pacific subtropical high followed by Typhoon Mina. In this study, we analyzed the effects of meteorological and photochemical processes on the O3 concentration in PRD during this episode by carrying out the Weather Research Forecast-Community Multiscale Air Quality (WRF-CMAQ) model simulations. Results showed that low relative humidity, high boundary layer height, northerly surface winds and strong downdrafts were the main meteorological factors contributing to O3 pollution. Moreover, delayed sea breezes that lasted into the night would transport O3 from the sea back to land and resulted in secondary O3 maxima at night. In addition, O3 and its precursors stored in the residual layer above the surface layer at night can be mixed down to the surface in the next morning, further enhancing the daytime ground-level O3 concentration the following day. Photochemical production of O3, with daytime average production rate of about 7.2 ppb/h, is found to be the predominate positive contributor to the O3 budget of the boundary layer (0–1260 m) during the entire O3 episode; while the horizontal and vertical transport fluxes are the dominant negative contributors. This O3 episode accounted for 10 out of the yearly total of 51 days when the maximum daily 8-h average (MDA8) O3 concentrations exceeded the national standard of 75 ppb in PRD in 2019. Based on these results, we propose that the enhanced photochemical production of O3 during the episode is a major cause of the most severe O3 pollution year since the official O3 observation started in PRD in 2006. Moreover, since this O3 episode is a synoptic scale phenomenon covering the entire eastern China, we also suggest that the enhanced photochemical production of O3 in this O3 episode is a major cause of the extraordinary high O3 concentrations observed in eastern China in 2019.

Shanshan Ouyang et al.

Status: open (until 14 Jul 2022)

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  • RC1: 'Comment on acp-2022-290', Anonymous Referee #1, 12 Jun 2022 reply

Shanshan Ouyang et al.

Shanshan Ouyang et al.

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Short summary
A record-breaking severe O3 pollution episode occurred under the influence of a Pacific subtropical high followed by Typhoon Mina in the Pearl River Delta (PRD) in early Autumn 2019. Through the WRF-CMAQ model simulations, we propose that the enhanced photochemical production of O3 during the episode is a major cause of the most severe O3 pollution year since the official O3 observation started in PRD in 2006.
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