京津冀地区持续性雾霾天气的稳定分量提取和预报方法研究

In recent years, the problem of fog and haze has drawn more and more attention from more and more people. Especially the persistent fog and haze weather in Beijing-Tianjin-Hebei Region has a far-reaching impact. The existing researches mainly focus on the causes of fog-haze weather and the changing trend, but there are not many studies on improving the forecast of the fog-haze weather, especially the improvement of the persistent fog and haze weather forecasting. Accurately forecast the persistent fog and haze weather is an important prerequisite for dealing with haze weather hazards. This project intends to analyze the circumstance of the persistent fog and haze weather circulation in Beijing-Tianjin-Hebei Region by means of filtering, empirical orthogonal function decomposition and other methods to extract the characteristic stable components that affect their elimination and development in the extension period(10-30 days). On the basis of this, a continuous circulation fog-haze mechanism for the formation and maintenance of fog-haze weather is to be established. Based on the stable component, the numerical prediction experiment is also needed. Based on the degree of freedom of the initial field and the intermediate prediction field in the compression mode, the Stable component information is refined to improve the prediction effect of the numerical model for the persistent fog and haze weather. By searching for the persistent fog and haze weather in the prediction field, Hazardous weather "precursor signal" and "feature stable component" to improve the numerical model of the persistent fog and haze weather forecasting skills.

近年来，雾霾问题愈来愈受到社会各界广泛关注，其中京津冀地区的持续性严重雾霾天气影响尤为深远。已有的研究多集中在雾霾天气成因及变化趋势等方面，而关于雾霾预报方法改进尤其是持续性雾霾天气预报技术的改进研究还不多，准确地预报雾霾天气是应对雾霾天气危害的重要前提。本项目拟通过分析京津冀地区持续性雾霾天气环流形势，采用滤波、经验正交函数分解等方法，提取延伸期（10～30d）尺度内影响其生消和发展维持的“特征稳定分量”，在此基础上建立持续性雾霾天气形成和维持的环流机制，并基于稳定分量开展数值预报改进试验，通过压缩模式初始场和中间预报场的自由度，凝练稳定分量信息，改进数值模式对于持续性雾霾天气的预报效果，并通过在预报场中检索持续性雾霾天气的“前兆信号”和“特征稳定分量”，提高数值模式对持续性雾霾天气的预报技巧。

如何防治和应对雾霾天气，是各级政府和公众普遍关注的一个重要问题，研究京津冀地区持续雾霾的影响机制及预报改进技术具有重要的科学意义和现实价值。本项目分析了京津冀地区持续性雾霾天气分布特征，提取了影响雾霾的“特征稳定分量”和“前兆信号”，在此基础上阐明了持续性雾霾天气的影响机制，并基于稳定分量开展数值预报改进实验，提高了数值模式对持续性雾霾天气的预报技巧。研究发现：一是1981～2020年京津冀地区雾霾天气整体呈现南多北少的分布形势，西南部最为严重，北部最轻。雾霾在2010年以后呈明显加重趋势，其中2011～2015年雾霾尤为明显，在2016～2020年雾霾得到有效控制。二是通过研究明确了京津冀地区典型持续雾霾过程的环流稳定分量及其影响机制。在持续雾霾时段位势高度场稳定分量中“三极子”结构，与欧亚大陆中高纬较强的纬向环流形势（风场U分量稳定分量典型特征）相配合，使得京津冀地区呈现少冷空气活动、暖湿气流控制等特征，为该地区出现持续性雾霾天气提供有利条件。三是研究了京津冀地区持续性雾霾天气的稳定分量“前兆信号”及其可预报性。在持续雾霾过程发生前风场U分量稳定分量中存在一个重要“前兆信号”，即在欧亚大陆中纬度地区存在一个强盛的带状偏西风距平区。温度场稳定分量的前兆信号与风场U分量有很大相似性，位势高度场稳定分量前兆信号则出现较晚，且分布层次也相对较浅薄。四是评估了S2S多模式对持续雾霾环流形势的预报能力，CMA模式在中低层预报效果最好，ECMWF模式在全部层次预报效果均较好；进一步基于演化误差增长情况筛选S2S多模式的最优可预报稳定分量，改进了模式对持续雾霾的预测技巧。结果表明，在对流层上层仅ECMWF模式预报改进效果较好；在对流层中下层各模式均有不同程度的提高，ACC提高最多可达0.26，预报改进效果较为明显。