2022年9月福建邵武边界层臭氧异常升高的气象成因

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

【目的】为揭示边界层O_(3)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、O_(3)探空观测科学试验基地)出现边界层O_(3)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)O_(3-1h)较多年平均值增长137.1%;边界层O_(3)体积混合比(OVMR)明显高于不同季节的平均状态,21日O_(3)探空观测到边界层O_(3)总量为全年同层探空观测的极大值。O_(3)异常升高是副热带高压和3个台风外围下沉气流共同影响的结果,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O_(3)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4~8 m·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O_(3)光化学生成,另一方面有利于上风向高浓度O_(3)水平输送和边界层高浓度O_(3)垂直下沉侵入,而后者是O_(3)异常升高的主要来源。

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 O_(3) 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 O_(3) Sounding Observation Scientific Experimental Base)so as to reveal the causes for the abnormal increase of O_(3) 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(O_(3-8h))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 O_(3-1h) concentration rose by 137.1%.The boundary layer O_(3) 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 O_(3) 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 O_(3) level of boundary layer on the 7 th 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 O_(3),and also favorable for the horizontal transport of O_(3)-rich air from upwind areas and the downward intrusion of O_(3) into the boundary layer.The latter is the main contributor to the anomalous increase in near-surface O_(3) concentration.