Dominant Patterns of Summer Ozone Pollution in Eastern China and Associated Atmospheric Circulations

Yin, Zhicong; Cao, Bufan; Wang, Huijun

doi:10.5194/acp-2019-430

Cited by 6 publications

(6 citation statements)

References 2 publications

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“…They found that O 3 pollution events in the YRD region mainly occurred between the end of a typhoon and the arrival of the next typhoon. Since fluctuations between highpressure and low-pressure systems strongly affect the variation in O 3 concentrations (Bachmann, 2015), the western Pacific subtropical high (WPSH) is also an important factor affecting O 3 in eastern China (Zhao and Wang, 2017;Chang et al, 2019;Yin et al, 2019). Numerical simulation studies by Zeren et al (2019) and Shu et al (2016) revealed that strong photochemical reactions and unfavorable diffusion conditions caused by the single/combined action of subtropical highs and typhoons are the main reasons for the occurrence of regional O 3 pollution.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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Abstract. A record-breaking severe ozone (O3) pollution episode occurred in the Pearl River Delta (PRD) in early autumn 2019 when the PRD was under the influence of a Pacific subtropical high followed by Typhoon Mitag. In this study, we analyzed the effects of meteorological and photochemical processes on the O3 concentration in the 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, weak northerly surface wind, 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 the 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 on the following day. Photochemical production of O3, with a daytime average production rate of about 7.2 ppb h−1 (parts per billion), 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 d when the maximum daily 8 h average (MDA8) O3 concentration exceeded the national standard of 75 ppb in the 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 the 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 extraordinarily high O3 concentrations observed in eastern China in 2019.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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“…Among these meteorological conditions, the daytime surface temperature is an important driver of ozone episodes. A high temperature can accelerate the chemical kinetic reaction and emissions of the natural components of ozone increase (Bloomer et al., 2009; Gu et al., 2020; Yin et al., 2019). This work thus focuses on developing an ozone forecasting model depending on temperature.…”

Section: Methodsmentioning

confidence: 99%

Spatio‐Temporal Hourly and Daily Ozone Forecasting in China Using a Hybrid Machine Learning Model: Autoencoder and Generative Adversarial Networks

Cheng

Fang

Navon

et al. 2022

J Adv Model Earth Syst

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Efficient and accurate real‐time forecasting of national spatial ozone distribution is critical to the provision of effective early warning. Traditional numerical air quality models require a high computational cost associated with running large‐scale numerical simulations. In this work, we introduce a hybrid model (VAE‐GAN) combining a generative adversarial network (GAN) with a variational autoencoder (VAE) to learn the dynamic ozone distributions in spatial and temporal spaces. The VAE‐GAN model can not only decipher the complex nonlinear relationship between the inputs (the past states/ozone and meteorological factors) and outputs (ozone), but also provide ozone forecasts for a long lead‐time beyond the training period. The performance of VAE‐GAN is demonstrated in hourly and daily spatio‐temporal ozone forecasts over China. The training datasets from 2013 to 2017 and validation datasets from 2018 to 2019 are the collection of data from the air quality reanalysis datasets. With the use of VAE, large dataset sizes are decreased by three orders of magnitude, enabling hourly and daily forecasts to be computed in seconds. Results show that the VAE‐GAN achieves a reasonable accuracy in the prediction of both the spatial and temporal evolution patterns of hourly and daily ozone fields, as compared to the Nested Air Quality Prediction Modeling System (commonly used in China), the reanalysis data and observations during the validation period. Thus, the VAE‐GAN is a cost‐effective tool for large data‐driven predictions, which can potentially reinforce air pollution prediction efforts in providing risk assessment and management in a timely manner.

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“…Mao et al (2020) made a comprehensive study of an 11-day O3 episode in BTH in 2017 and found it was dominated by the presence of the WPSH and mid-high latitude wave activities. Depending on the position and intensity, WPSH is well known to be an important factor affecting O3 concentrations in various parts of eastern China (Zhao and Wang, 2017;Chang et al, 2019;Yin et al, 2019). During this 11-day O3 episode, the ridge line of WPSH maintained at approximately 22°N from June 24 to June 29, which in combination with mid-high latitude wave activities induced meteorological conditions highly conducive to the O3 production in BTH and northern YRD (Mao et al, 2020).…”

Section: Cause(s) Of the Expansion And Saturationmentioning

confidence: 99%

What is the cause(s) of ozone trends in three megacity clusters in eastern China during 2015–2020?

Liu

et al. 2023

Preprint

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Abstract. Thanks to a strong emission control policy, major air pollutants in China, including PM2.5, SO2, NO2 and CO had shown remarkable reductions in 2015–2020. However, ozone (O3) had increased significantly and emerged as a major air pollutant in eastern China at the same time. The annual mean concentration of maximum daily 8-hour average O3 (MDA8) in three megacity clusters in eastern China, namely Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD), showed alarming large upward linear trends of 2.4, 1.1 and 2.0 ppb yr-1, respectively during the period 2015–2020. Furthermore, drastic trends of approximately three-fold increase in the number of O3-exceeding days (defined as MDA8 O3 >75 ppb) were observed during the same period. Our analysis of the upward trends of the annual mean concentration of MDA8 found that the trends were almost entirely attributable to the increase in the number of consecutive O3-exceeding days. In addition, a widespread expansion of high O3 from urban centers to surrounding rural regions was found in 2015–2017, which had made the O3 spatial distribution becoming more uniform after 2017. Finally, we found that the O3 episodes with four or more consecutive O3-exceeding days in the three megacity clusters were closely associated with the position and strength of the West Pacific subtropical high (WPSH), which contributed to the meteorological conditions characterized by clear sky, sinking motion and high vertical stability in the lower troposphere, and high solar radiation and positive temperature anomaly at the surface. These meteorological conditions were highly conducive to O3 formation. Hence we hypothesize that the cause of the worsening O3 trends in BTH, YRD and PRD from 2015 to 2020 is attributable to the increased occurrence of meteorological conditions of high solar radiation and positive temperature anomaly under the influence of WPSH, tropical cyclones as well as mid-high latitude wave activities.

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Dominant Patterns of Summer Ozone Pollution in Eastern China and Associated Atmospheric Circulations

Cited by 6 publications

References 2 publications

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

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

Spatio‐Temporal Hourly and Daily Ozone Forecasting in China Using a Hybrid Machine Learning Model: Autoencoder and Generative Adversarial Networks

What is the cause(s) of ozone trends in three megacity clusters in eastern China during 2015–2020?

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