南亚高压对四川盆地夏季区域持续性O3污染的影响

基于2015~2020年四川盆地臭氧（O₃）浓度监测数据，构建O₃区域性持续性污染过程个例库，并进一步时空匹配高低空气象资料，探究夏季南亚高压系统对四川盆地地面气象要素及O₃污染生成的影响机制.结果表明：（1）2015~2018年四川盆地O₃区域性持续性污染（ORPP）逐年加重，2018~2020年保持相对稳定的污染态势，且ORPP多集中于春、夏两季.盆地中南部成都、重庆、泸州等城市O₃污染形势最为严峻，且高值区逐渐向南北方向转移.（2）基于南亚高压（系统存在率、中心离散度与东西振荡量）对地面气象要素的影响阐释ORPP的生成机制：系统存在率均值偏低且位置偏东时，平均气温、气温日较差及日照时数偏高，相对湿度偏低，利于O₃生成；南亚高压东模态中心显著聚集时，气温日较差与日照时数激增，易造成O₃异常高值；西模态剧烈振荡时，气温日较差、日照时数及相对湿度改变，易使O₃浓度波动.（3）对比清洁期与污染期，南亚高压系统存在率、中心离散度与东西振荡量综合作用于清洁期，而污染期则主要受中心离散度与东西振荡量影响.当南亚高压西模态剧烈振荡与东模态显著聚集配合出现时，极易诱发四川盆地内ORPP二级过程.

Effects of South Asian High Pressure on regional persistent ozone pollution in Sichuan Basin during summer

Based on the monitoring data of ozone (O₃) concentration in Sichuan Basin from 2015 to 2020, a database of O₃ regional persistent pollution cases was constructed and further spatio-temporally matched with high and low altitude meteorological observation data. The effect of the South Asian High Pressure system (SAH) on the surface meteorological elements and O₃ pollution generation in Sichuan Basin during summer was investigated by applied this database. The O₃ regional persistent pollution (ORPP) in Sichuan Basin became worse from 2015 to 2018, while the pollution trend remained relatively stable from 2018 to 2020. And ORPP was mainly concentrated in spring and summer season. The situation of O₃ pollution was most severe in central-south part of the basin (especially in Chengdu, Chongqing, Luzhou), and the high value area gradually shifted to the north-south direction. (2) The mechanism of ORPP generation was explained based on the influence of SAH (system presence rate, center dispersion and east-west oscillation) on surface meteorological elements:When the mean value of system presence rate was low and the location was eastward, the average temperature, daily temperature difference and sunshine duration were high and the relative humidity was low, which was favorable for O₃ generation. When the eastern mode of SAH centers were significantly concentrated, the daily temperature difference and sunshine duration increased dramatically, which was tended to cause abnormally high O₃ concentrations; When the western mode of SAH oscillated dramatically, the change of daily temperature difference, sunshine duration and relative humidity could cause large fluctuations in O₃ concentrations. (3) Compared the clean period with the polluted period, the system presence rate, center dispersion and east-west oscillation of SAH had a combined effect on the clean period, while the polluted period was mainly influenced by the center dispersion and east-west oscillation. The regional persistent secondary pollution processes (ORPP₂) were prone to occur in Sichuan Basin, when the severe oscillation of western mode and the significant accumulation of eastern mode occurred simultaneously.