2022年9月福建邵武边界层臭氧异常升高的气象成因

【目的】为揭示边界层O₃异常升高及大气热力、动力条件对其影响的机理。【方法】该文基于多源观测资料，采用天气分型、统计合成和物理量诊断等方法，探究了2022年9月福建邵武（国家级气象探空站、O₃探空观测科学试验基地）出现边界层O₃异常升高的特征及大气热动力的综合作用。【结果】2022年9月邵武近地层O_3-8h异常正距平最高达125.4%；在非光化学时段（21时—次日07时）O3较多年平均值增长137.1%；边界层O₃体积混合比（OVMR）明显高于不同季节的平均状态，21日O₃探空观测到边界层O₃总量为全年同层探空观测的极大值。O₃异常升高是副热带高压和3个台风外围共同影响的结果，导致全月较30 a气候态平均呈现：太阳辐射偏强、低云量偏少、地面气温升高，相对湿度偏低、降水量偏少，偏北风持续时间长且风速偏大；7日和21日边界层O₃总量高值日的气象探空廓线呈现大气层结稳定、空气干燥、湿层薄，同时下沉对流有效位能DCAPE值较高，在200～800 J·kg_-1之间，即存在明显的下沉气流；低层主导风为偏东风，风速在4～8m·s_-1之间。【结论】气象要素配置与大气的热力、动力条件一方面有利于O₃光化学生成，另一方面有利于上风向高浓度O₃水平输送和边界层高浓度O₃垂直下沉侵入，而后者是O₃异常升高的主要来源。

Meteorological Causes of Boundary-layer Ozone Surge in September 2022 over Shaowu of Fujian Province

Using the multi-source observation data and the methods such as weather classification, statistical synthesis, and physical quantity diagnosis, this article explores the characteristics of abnormal increase of O₃ in the boundary layer and the comprehensive application of atmospheric thermodynamics in September 2022 at Shaowu Station of Fujian Province (a National Meteorological Sounding Station and O₃ Sounding Observation Scientific Experimental Base) so as to reveal the causes for the abnormal increase of O₃ in the boundary layer and the mechanism of the influence of atmospheric thermodynamic and dynamic conditions on it. The results show that in September 2022, the near-surface daily maximum 8 h average ozone concentrations (O3-8h) in Shaowu increased by 125.4% at most compared to the long-term (2015—2021) mean. Particularly, during the non-photochemical period from 21 o’clock to the next 7 o’clock, the O3-1h concentration rose by 137.1%, reaching 2.37 times the long-term average. The boundary layer O₃ volumetric mixture ratio (OVMR) surpassed the seasonal average significantly, and the observed total ozone column on September 21 reached its maximum in the same layer throughout the year. The surge in O₃ level primarily resulted from the combination effects of subtropical high-pressure systems and the peripheries of three typhoons during September 2022, which led to a noticeable rise in solar radiation, reduced cloud cover, rising surface temperature, lowered relative humidity, and less precipitation as well as long-lasting strong northerly winds. The high O₃ level of boundary layer on the 7th and the 21st occurred under a stable atmospheric stratification with dry air and thin moist layer. In the meantime, the value of downward convective available potential energy (DCAPE) was relatively high, ranging from 200 to 800 J·kg-1, and the easterly winds prevailed in the lower levels at speed of 4-8 m·s-1. To sum up, the configuration of meteorological elements and the thermodynamic and dynamic conditions are favorable for the photochemical production of O₃, and also favorable for the horizontal transport of O₃-rich air from upwind areas and the downward intrusion of O₃ into the boundary layer. The latter is the main contributor to the anomalous increase in near-surface O₃ concentration.