In recent years, surface ozone (O₃) has increased rapidly over the North China Plain (NCP), which is harmful to human health and crop yields. Summertime O₃ over the NCP is remarkably influenced by the East Asian summer monsoon (EASM), while the distinctions of their relations in different monsoon periods are still vague. In this study, we divided the whole monsoon season into the pre-flood period, the Meiyu flood period, and the post-flood period. For each monsoon period, we examined the characteristics and variations of O₃ from 2014 to 2019 and the associated atmospheric circulations individually. Based on a multiple linear regression model, we further quantified the meteorological contributions to the year-by-year variation and increasing trend in O₃ during different monsoon periods. We found that the maximum daily 8 h-average O₃ concentration (O₃_MDA8) exhibits subseasonal variations on the mean level (72.5, 76.7, and 63.8 ppb) and trends (3.2, 4.0, and 1.7 ppb yr⁻¹) during the three monsoon periods. Meteorological variations account for 58.9% and 58.6% of the O₃ uptrends in the Meiyu flood and the pre-flood periods but exert adverse effects on the O₃ increase in the post-flood period (−27.4%). The positive meteorology-driven trend in the pre-flood period is attributed to increased radiation and temperature, and that in the Meiyu flood period is contributed by the rise in radiation and decrease in relative humidity. While in the post-flood period, the decreasing trend mainly results from the increased precipitation. The subseasonal discrepancy is related to the distinct dominance of wave activities in the mid-and-high latitudes and the western Pacific subtropical high (WPSH) in different monsoon periods. The anomalously high pressure conduces to the high-level O₃ over the NCP in the pre-flood period. Frequent O₃ pollution in the Meiyu flood period is caused by the strong wave amplitudes in the mid-and-high latitudes and a westward stretched and intensified WPSH. While in the post-flood period, the east-west shift of WPSH modulates the precipitation and O₃ variations over the NCP region. Among the three periods, we highlighted the Meiyu flood period for the highest O₃ level and the most drastic increasing trend, during which more strict emission control should be implemented.

近年来，华北平原（NCP）的地表臭氧（O ₃）迅速增加，对人类健康和作物产量有害。NCP上空的夏季O ₃受东亚夏季风（EASM）的影响显着，但它们在不同季风时期的关系的区别仍然模糊。在本研究中，我们将整个季风季节划分为洪水前、梅雨洪水期和洪水后时期。对于每个季风期，我们分别检查了2014 年至 2019 年O ₃的特征和变化以及相关的大气环流。基于多元线性回归模型，我们进一步量化了气象对 O 的逐年变化和增加趋势的贡献。₃在不同的季风时期。我们发现，最高每日 8 小时平均 O ₃浓度 (O ₃ _MDA8) 在平均水平（72.5、76.7 和 63.8 ppb）和趋势（3.2、4.0 和 1.7 ppb yr ^-1）上表现出亚季节变化。三个季风期。气象变化占58.9％和O的58.6％₃在梅雨洪水上涨趋势和预汛期，但发挥的Ø不利影响₃洪水后增加（-27.4%）。洪水前气象驱动的正趋势归因于辐射和温度的增加，梅雨洪水期的趋势是辐射上升和相对湿度下降。而在后洪水期，下降趋势主要是由于降水增加。亚季节差异与不同季风时期中高纬度和西太平洋副热带高压（WPSH）的波浪活动具有明显优势有关。异常高压导致前洪水期NCP上空O ₃高。频繁的O ₃梅雨洪水期的污染是由中高纬度地区的强波幅和向西伸展和加强的副高造成的。而在后洪水时期，副高的东西向偏移调节了NCP地区的降水和O ₃变化。三个时期中，我们突出了O ₃水平最高、上升趋势最剧烈的梅雨汛期，在此期间应实施更严格的排放控制。