Abstract Pollution weather may cause serious damages to human life and property. Meteorological conditions like large-scale circulation can affect the formation and dissipation of pollution weather. We apply the hierarchical clustering method to classify circulation patterns based on the National Centers for Environmental Prediction (NCEP) Final Operational Global Analysis (FNL) sea level pressure (SLP) daily data and investigate their features during the formation and dissipation process of the defined 31 continuous pollution weather (CPW) cases in the Sichuan Basin using the meteorological data from 104 surface observation stations during 2007–2017. We find that the Sichuan Basin during the formation process is controlled by the large scale high-pressure circulation at sea level, and the SLP can be divided into high-pressure front type FC1 (32%) with the high pressure located in the west of the Basin, weak high-pressure type FC2 (35%) with the weak high pressure located in the Basin, and uniform pressure field type FC3 (33%) with the near homogeneous pressure distributed in the Basin. The Sichuan Basin during the dissipation process is dominated by the low-pressure circulation at sea level, and the SLP can be classified as low-pressure type DC1 (35%) with the low pressure centralize in the Basin, low-pressure front type DC2 (38%) with the low pressure center in the west of the Basin, and low-pressure bottom type DC3 (27%) with the low pressure in the north of the Basin. Besides, the wind, relative humidity, geopotential height, and temperature data are used to explore the formation and dissipation mechanisms of the CPW. The wind speed and temperature are lower during the formation phase of the CPW compared to those from the dissipation phase. Furthermore, we estimate the effects of the CPW on pollutants based on the air quality index and Particulate Matter (PM10 and PM2.5) concentration from environmental protection monitoring data during 2013–2017. The FC2 type shows the strongest enhancement of pollutants (36%), and the DC3 circumstance generates the most efficient scavenging mechanism to dispel pollutants (−57%).

中文翻译：

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四川盆地持续污染天气形成与消散过程中的环流模式分类

摘要 污染天气可能对人类生命财产造成严重损害。大环流等气象条件会影响污染天气的形成和消散。我们应用层次聚类方法对基于国家环境预测中心 (NCEP) 最终业务全球分析 (FNL) 海平面压力 (SLP) 每日数据的环流模式进行分类，并研究它们在定义的 31使用 2007-2017 年 104 个地面观测站的气象数据分析四川盆地的连续污染天气（CPW）案例。我们发现四川盆地在形成过程中受海平面大规模高压环流控制，SLP可分为高压前沿型FC1（32%），高压位于盆地西部，弱高压FC2型（35%）位于盆地西部，弱高压位于盆地。 FC3 型均匀压力场（33%），盆地内分布近乎均匀的压力。消散过程中四川盆地以海平面低压环流为主，海平面低压型DC1（35%），低压集中于盆地，低压锋型DC2 (38%)，盆地西部低压中心，低压底型DC3(27%)，盆地北部低压。此外，利用风、相对湿度、位势高度和温度数据来探索CPW的形成和消散机制。与消散阶段相比，CPW 形成阶段的风速和温度较低。此外，我们根据 2013-2017 年环境保护监测数据中的空气质量指数和颗粒物（PM10 和 PM2.5）浓度估计了 CPW 对污染物的影响。FC2型显示出最强的污染物增强（36%），DC3环境产生最有效的清除污染物的清除机制（-57%）。