• 关键词：臭氧污染  天气分型  案例分析  成都平原

• 基金项目：国家重点研发计划（No.2018YFC0214002，2018YFC0214001）；四川省科技计划项目（No.2018SZDZX0023，2018JY0011）；成都市科技局技术创新研发项目（No.2018-YF05-00219-SN）

• 卢宁生
• 成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都 610225

• 张小玲
• 成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都 610225

• 康平
• 成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都 610225

• 华明
• 成都市气象局, 成都 610072

• 杜云松
• 四川省生态环境监测总站, 成都 610091

• 陈军辉
• 四川省生态环境科学研究院, 成都 610042

• 向卫国
• 成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都 610225

• 雷雨
• 成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都 610225

• 欧奕含
• 成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都 610225

• 摘要：通过分析成都平原城市群8个城市2015—2019年春季（4—5月）地面臭氧浓度及超标情况表明，春季成都平原平均臭氧日最大8小时平均浓度（O₃_8 h）呈上升趋势，成都、眉山O₃超标日较多，雅安最少但呈逐年增加趋势，资阳、乐山O₃_8 h平均值和O₃超标率高于夏季.同时，利用ERA-Interim再分析资料和PCT客观天气分型方法，对近5年春季成都平原及周边海平面气压场、700 hPa和500 hPa的位势高度场进行客观分型研究以揭示重污染期间高低空天气型配置，并分析天气系统及气象要素与臭氧污染的关系.结果表明：①成都平原春季容易发生O₃污染的地面天气形势为低压场和均压场，气象特征表现为高温低湿、强辐射、小风、混合层较高、有弱的辐合运动，该天气型下成都市平均O₃_8 h达140 μg·m^-3.②700 hPa臭氧污染天气形势为南支槽和高原低涡型，500 hPa为南支槽和平直纬向型.高空为南支槽的环流形势下，地面均压和低压场的占比超过六成.污染较重的月或年份，地面、700 hPa和500 hPa污染天气型占比均较高.③对近5年春季成都平原持续O₃污染过程分析发现，污染前期，成都平原处于地面高压后部或均压场中，随着700 hPa低值系统东移，其前部暖平流和正涡度平流的输送，促使平原地区整层大气增温及地面天气型由均压场向低压场转变.④污染过程中，500 hPa高空气流受高原-盆地地形的作用发生下沉，与地面低压场的辐合上升运动促进了低层局地环流的形成，这一方面限制了污染物向高层的扩散，另一方面造成边界层内O₃的下传，加重成都平原O₃污染的程度.

• Abstract：The analysis of the surface ozone concentration and exceeded rate in 8 cities in the Chengdu Plain urban agglomeration during the spring of 2015 to 2019 (April to May) showed that the maximum daily 8 h O₃ mass concentration (O₃_8 h concentration) of plain in the spring presented an upward trend. Chengdu and Meishan had more O₃ over-standard days, Ya'an was the least but it was increasing year by year, the average O₃_8 h concentration and exceeded rate in Ziyang and Leshan were higher than that in summer. Using the ERA-Interim reanalysis data and the PCT objective weather classification method, the sea-level pressure field, 700 hPa and 500 hPa geopotential height fields over Chengdu Plain and its surrounding were objectively classified in the spring for the past five years, revealed the high and low altitude weather configuration during heavy pollution, and analyzed the relationship between weather system and meteorological elements and ozone pollution. The results showed that: ①The surface weather conditions that were prone to O₃ pollution in the Chengdu Plain during spring were low pressure field and equal pressure field, with the meteorological characteristics were high temperature, low humidity, strong radiation, small wind, high mixed layer, and weak convergence movement. The average O₃_8 h concentration in Chengdu under this weather classification was 140 μg·m^-3. ② The 700 hPa ozone pollution weather classification was the southern branch trough and plateau low vortex type, and the 500 hPa was the southern branch trough and the flat vertical zonal type. In the high-altitude circulation situation where the south branch trough was present, the surface pressure equalization and low pressure field accounted for more than 60%. In severely polluted months or years, the surface, 700 hPa, and 500 hPa polluted weather types accounted for a higher proportion. ③Analysis of the continuous O₃ pollution process in the Chengdu Plain in the spring of the past five years found that in the early stage of pollution, the plain was in the back of the high pressure system or in the equalizing field of the surface, as the 700 hPa low-value system moved eastward, the transport of warm advection and positive vorticity advection in the front promotes the entire layer of atmosphere to increase in the plain area and the surface weather pattern changed from a pressure equalization field to a low pressure field. ④ During the pollution process, the 500 hPa high-air flow sinked under the action of the plateau-basin topography, and the convergence with the low-pressure field of the surface promoted the formation of low-level local circulation, which restricts the diffusion of pollutants to the upper level. In addition, it caused the downward transmission of O₃ in the boundary layer, which increased the degree of O₃ pollution in the plain.

• Key words：ozone pollution  weather classification  case analysis  Chengdu Plain

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