冬春季四川盆地西南涡活动对大气复合污染影响与机制研究

It is well known that the southwest vortex occurring in the summer and autumn is one of the severe rainstorm-producing weather systems in the southwest China, Yangtze River valley, southern Shanxi, and North China and then has attracted much attention. However, little attention has been paid to the influence of the southwest vortex generated in the winter and spring on the complex air-pollution. The preliminary result shows that the regional severe air-pollution event during the winter and spring in the Sichuan Basin is closely related with the activities of the southwest vortex. Given this phenomenon, using systematic metrology of observation experiments, statistic diagnosis and numerical simulation, the proposal will perform systematic study on the influence of the winter/spring southwest vortex in the basin on the complex air pollution. The principal objectives are summarized as follows. It is to document the temporal and spatial distribution characteristics of various air pollutants and their relationship with the southwest vortex activities as well as to understand meteorological features of air pollution during southwest vortex activities and their impacts on the air pollution. The project will reveal the influences of generation and disappearance processes of the southwest vortex on the atmospheric boundary layer structure and air pollution and their feedback mechanisms through numerical simulation. It is going to explore the impacts of eastward traveling of the southwest vortex transporting high concentration air-pollutant on the acidity and intensity of attendant precipitation in the downstream regions and the mechanisms. In addition, The research will clarify multi-scale meteorology collaboration and its influence on the complex air-pollution processes in the basin, and the relevant concept model will be constructed. The project will serve as an important scientific basis for air pollution forecasting and effective prevention and cure in the basin.

众所周知，夏秋季节的西南涡活动是造成我国西南地区、长江流域、陕南、甚至华北暴雨的重要降水系统之一，倍受关注。然而，冬春季西南涡活动对大气复合污染的影响却尚未引起重视。本项目基于初步研究发现四川盆地冬春季区域性大气重污染过程都与西南涡活动密切相关这一事实，拟采用观测试验、诊断分析与数值模拟相结合的研究方法，对盆地内冬春季西南涡活动对大气复合污染的影响进行系统研究，探明不同污染物时空分布及其与西南涡活动之间的关系；搞清盆地西南涡活动期间的污染气象特征及其对大气污染的影响；通过数值模拟试验，揭示西南涡生、消过程对盆地内大气边界层结构与大气污染的影响及互馈机制；探究含有高浓度污染物的西南涡东移对邻近下游地区降水酸化程度与降水强度的影响与机理；明晰多尺度气象条件协同作用及其对盆地大气复合污染过程的影响，构建其概念模型。为四川盆地空气污染预报、环境容量评估及其防治提供科学依据与本地化模式。

本项目从污染气象学的角度对冬春季四川盆地西南涡活动对大气复合污染影响与机制进行深入系统的研究。探明了四川盆地冬春季不同污染物时空分布特征，首次研究揭示了盆地不同部位（盆底、盆边、盆沿）空气污染三维空间变化特征，给出了边界层PM2.5和PM10浓度随高度垂直递减的二次函数式；指出成都冬季重空气污染过程的持续时间显著长于北京和上海，存在诱发大气污染暴露健康风险的可能性。对其与西南涡活动关系的研究，率先发现冬春季干西南涡存在明显加剧大气污染的效应，尤其是区域性大气重污染过程几乎都与干西南涡活动密切相关，这与夏秋季湿涡降水对大气的净化效应截然不同；搞清了盆地西南涡活动期间的污染气象参数特征及其对大气污染影响和预报的指示意义；通过诊断分析与数值模拟研究，揭示了不同类型的西南涡对四川盆地大气边界层结构及空气污染的影响。首次发现干西南涡的空降“锅盖效应”，并揭示其对盆地重空气污染过程的影响机制，指出“锅盖效应”迫使局地次级环流局限于大气边界层内，压缩大气污染物扩散空间，其垂直混合和水平扩散受到限制，呈现出深盆地形特有的、多尺度系统叠置、结构复杂的静稳型天气特征，造成边界层内大气污染物暴发式增长的重污染事件。在此基础上，又从全球尺度的海-气协同作用入手，剖析了我国西南地区（包括四川盆地）冬季空气污染与干旱大气环流背景及海-气遥相关型之间的关联性，揭示了高原南支槽活动与四川盆地大气污染之间的关系，至此探明了全球尺度的海-气协同作用、区域大气环流（南支槽）、天气尺度系统（短波槽）、中尺度系统（西南涡）、局地次级环流等多尺度气象条件的配置关系与协同作用及其对四川盆地大气重污染过程的综合影响，构建出了盆地冬季大气复合重污染的多尺度气象条件耦合影响机制概念模型，丰富和发展了污染气象学的理论内涵，圆满完成了预期研究目标。此成果可为四川盆地空气质量预报、大气环境容量评估以及污染防治提供新的科学依据。