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2022年夏季历史极端高温下我国近地表臭氧污染及气象成因分析

Analysis of Surface Ozone Pollution and Its Meteorological Causes in China during the Record Summertime Extreme Heat of 2022

  • 摘要: 基于国家空气质量监测网和ERA5(欧洲中期天气预报中心第五代大气再分析数据集)气象数据,本文分析了2022年夏季历史极端高温条件下我国臭氧(O3)污染的变化及主要的气象驱动因素。从空间分布上,2022年夏季全国O3浓度呈现明显的反弹,6月的华北地区、7~8月的南方地区较为明显;从长期趋势上,华北2022年6月O3浓度为2015年以来同期第二高,导致区域内平均超标21 d;长江三角洲和四川盆地2022年7、8月的O3浓度均是2015年来同期最高。从前体物变化来看,卫星数据显示2022年NOx排放相对于2019~2021年无明显的变化,同时南方地区HCHO(甲醛)柱浓度的显著升高与温度变化十分一致,表明2022年极端高温事件是导致O3浓度异常偏高的主要驱动因素。具体来说,2022年O3异常与温度异常的空间相关系数在6~8月份分别达0.71、0.64和0.49,且重点城市O3的温度敏感性也比较高;从环流系统来看,O3异常升高与副热带高压控制下的高温、低湿的静稳天气有较强的时空一致性。特别地,2022年极端高温事件下O3对温度响应与过去相比有所不同,观测上逐日O3与温度的高正相关关系在达到某个阈值后会消失,但2022年华北和长江三角洲在较高的温度下依然存在正相关关系。本研究强调了极端高温事件对O3污染的影响的重要作用,对我国复合污染协同治理提出了更严峻的挑战。

     

    Abstract: In this study, the authors analyze surface ozone (O3) pollution and its dominant meteorological drivers in China based on the record summertime extreme heat of 2022 using Chinese national air quality network measurements and EAR5 reanalysis meteorological fields. Spatially, the O3 concentration across China remained high in the summer of 2022, with strong positive anomalies over northern China in June and southern China in July–August. For long-term trends, the O3 concentration in the North China Plain (NCP) in June 2022 was the second highest in June since 2015, resulting in 21 regionally averaged ozone exceedance days. In July–August 2022, O3 concentrations were the highest for these months since 2015 in the Yangtze River Delta (YRD) and Sichuan Basin (SCB). In terms of ozone precursor changes relative to 2019–2021, there was only a slight change in satellite-derived NO2 columns in 2022, while the enhancement in satellite-derived HCHO over southern China was consistent with temperature changes. This suggests that the record-breaking summertime extreme heat of 2022 is the dominant driver of O3 enhancement. Specifically, the spatial correlation coefficients between the O3 and temperature anomalies in 2022 were 0.71, 0.64, and 0.49 for June, July, and August, respectively; additionally, O3 sensitivity to temperature was relatively high in major clusters. Under the control of the subtropical high, the enhanced O3 concentration exhibits a strong spatiotemporal consistency with stagnant weather conditions characterized by high temperature and low humidity. In particularly, the O3–temperature relationship in 2022 was quite different from that of previous years, while the strong positive correlation observed for O3–temperature was suppressed when reaching a high-temperature threshold in 2019–2021. This positive correlation persisted even at extremely higher temperatures in 2022 in the NCP and YRD. This study highlights the important role of extreme high-temperature events on O3 pollution, which poses a pressing challenge for the synergistic control of complex air pollution issues in China.

     

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