In recent years, China has made certain progresses regarding the monitoring of ozone (O3) pollution. However, a comprehensive understanding of the three-dimensional distribution and evolutionary characteristics of O3 is still relatively lacking. This study analyzed an O3 pollution episode in the Pearl River Delta during September to October 2019 using data from five O3 lidars and air pollution monitoring stations combined with the Gridpoint Statistical Interpolation data assimilation system. The model's performance in the vertical direction improved after assimilation, with the correlation coefficient of model simulations improving by 87 %, errors decreasing by 30 %, and simulation accuracy increasing by 29 %. Results showed that O3 pollution persisted for more than a week due to high temperatures and the influence of Typhoon Mita. However, after October 2, the concentration of O3 decreased under the combined effects of southerly winds and reduced traffic emissions during the National Day period. Besides, lidar observations indicate that residual O3 at night can disrupt its typical diurnal variation patterns. Moreover, O3 pollution occurred both at ground level and greater heights. Overall, O3 is primarily produced by photochemical reactions. Nevertheless, the O3 concentration was also affected by pollutant transport from northeast to southwest at a height of 0–3 km during the pollution period, with an average transport flux of 366 μg·m−2·s−1. Anomalously high nighttime O3 concentrations (>100 μg·m−3) were observed in both coastal and inland cities. Residual O3 could lead to persistent pollution the next day. The results clarify the vertical distribution and evolutionary characteristics of O3, which is crucial for devising more targeted pollution control strategies in the Pearl River Delta.

中文翻译：

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基于激光雷达观测网和资料同化的珠江三角洲臭氧污染垂直分布及输送特征


近年来，我国在臭氧（O3）污染监测方面取得了一定进展。然而，对O3的三维分布和演化特征的全面认识还比较缺乏。本研究利用五个O3激光雷达和空气污染监测站的数据，结合网格点统计插值数据同化系统，分析了2019年9月至10月珠三角地区的一次O3污染事件。同化后模型垂直方向性能得到改善，模型模拟相关系数提高87%，误差降低30%，模拟精度提高29%。结果显示，由于高温和台风“美达”的影响，O3污染持续了一周多。但10月2日后，在南风和国庆期间交通排放减少的共同影响下，O3浓度有所下降。此外，激光雷达观测表明，夜间残留的 O3 会扰乱其典型的昼夜变化模式。此外，O3 污染同时发生在地面和更高的高度。总体而言，O3 主要由光化学反应产生。但污染期间0~3 km高度处O3浓度也受到东北向西南方向污染物输送的影响，平均输送通量为366 μg·m−2·s−1。沿海和内陆城市夜间 O3 浓度异常高（>100 μg·m−3）。残留的 O3 可能会导致第二天持续污染。 研究结果阐明了O3的垂直分布和演化特征，这对于制定更有针对性的珠三角污染控制策略至关重要。