等压面非地转分解诊断方法及其在冬季华南准静止锋垂直环流形成机理中的应用

South China quasi-stationary front was formed between southern warm air and northern cold air decreased by the surface friction and block of Nanling Mountain at South China. In winter, due to the increasing cold air, South China quasi-stationary front moves southward and is located between the south of Nanling mountain and Guangdong Province. The long-lasting and slowly moving front is the one of direct weather systems that induce the severe wither storm in the south of China. So, it is important to do some research about it. However, because South China quasi-stationary front sits at lower-latitude in winter and affected by friction and blocking effects of Nanling Mountain, the atmosphere shows the apparent ageostrophic feature, the well-developed quasi-geostrophic(QG) theory and according diagnostic methods cannot be satisfied. Hence, from hydrostatic primitive equations, adopting the idea of splitting analysis, a new ageostrophic splitting diagnostic method as well as the ageostrophic frontal vertical circulation equation will be proposed on isobaric coordinate in this project. From advection and adjustment process, we can quantitatively diagnose and analyze how the instantaneous effects are step-by-step operating on the formation of South China quasi-stationary frontal vertical circulation. And this study will help us to further understand the dynamical mechanism of South China quasi-stationary front in winter.

华南准静止锋是指当北方冷空气南下受到地面摩擦或南岭山脉阻挡后势力减弱，与南方北上的暖空气在华南地区相汇而形成的东西向分布的准静止锋。冬季，华南准静止锋位置偏南，多在南岭以南至广东地区，存在时间长、移动缓慢，是造成我国南方冬季大范围持续性雨雪冰冻灾害的最直接影响系统。因此，加强冬季华南准静止锋的相关研究十分必要。但是由于冬季华南准静止锋所处纬度较低，同时受地面摩擦和山脉阻挡，大气运动呈现出明显的非地转特征，准地转理论不再适用，该理论体系下成熟动力诊断方法的使用也受到限制。为了能更好地深入理解冬季华南准静止锋的动力机制，本项目拟从原始方程组出发，发展出一套适用于低纬非地转大气的等压面分解诊断新方法，从中推导出物理意义明确、有具体解法的非地转锋面垂直环流方程，并将其应用到冬季华南准静止锋分析中，从大气产生的不平衡强迫及其强迫下的调整变化这一角度定量诊断分析冬季华南准静止锋垂直环流的形成机理。

华南准静止锋是我国南方冬季大范围持续性雨雪冰冻灾害的最直接影响系统。由于冬季华南准静止锋所处纬度较低，同时受地面摩擦和山脉阻挡，大气运动呈现出明显的非地转特征，准地转理论不再适用，该理论体系下成熟动力诊断方法的使用也受到限制。为了能更好地深入理解冬季华南准静止锋的动力机制，本项目从原始方程组出发，发展出一套适用于低纬非地转大气的等压面分解诊断新方法，并从中推导出物理意义明确、有具体解法的非地转锋面垂直环流方程。同时，项目研究发现，华南准静止锋可基本分为两类，一类是局地生成的准静止锋，这类准静止锋生存时间较短，往往只伴随着华南弱的阴雨天气；第二类是冷锋南下转准静止锋类型，这类静止锋生命时间长，往往能引起大范围强烈的低温暴雨天气。这两类锋面尽管具有相同的大尺度天气系统，但其高低层天气系统的相互位相及其引发的非地转锋面垂直环流存在很大差异。项目建立的非地转诊断方法可以很好地应用到冬季华南准静止锋天气研究中，可从大气产生的不平衡强迫、以及该强迫下的调整变化角度定量诊断分析各类华南准静止锋垂直环流的形成机理，这对冬季华南准静止锋发生发展动力机制的理解具有重要意义。