乌拉尔山两类持续异常流型建立和衰退的超临界叉式分岔理论

乌拉尔山地区经常出现持续性的大气环流正异常和负异常，典型代表分别是阻塞高压和切断低压，它们往往是我国出现持续性异常天气和气候事件的重要原因之一。5-30天尺度上，正、负两类持续异常流型的建立和衰退，一直是机理研究和业务预报的难点。申请人前期研究发现，太阳常数与乌拉尔山地区正常型、正异常和负异常三类流型之间的关系，遵循超临界叉式分岔理论：（1）三类流型均具有持续性和反复再现性，可视为三种平衡态；（2）若太阳常数小于临界值1360.9Wm-2，正、负异常都是优势流型，且二者是等概率出现的；否则，正常型是唯一的优势流型。本项目拟推广超临界叉式分岔理论，研究任意一种强迫因子对乌拉尔山两类持续异常流型建立和衰退的影响遵循超临界叉式分岔理论所要满足的充分必要条件。进而通过分岔临界点，建立常见强迫因子与乌拉尔山两类持续异常流型之间的定量关系，为提高我国持续性异常天气和气候事件的预测能力提供理论依据。

The persistent positive and negative atmospheric circulation anomalies, typically associated with the blocking high and cut-off low, respectively, often occur over Ural Mountains. Usually, they are one of the important causes of the persistent anomalous weather and climate events occurred in China. On time scale of 5~30 days, the onset and decay of these two persistent anomalous flow patterns remain a difficult problem for the mechanism research and operational forecast. Our previous studies found that, the relationship between the total solar irradiance (TSI) and three Ural flow patterns, namely, neutral-type, positive-anomaly and negative-anomaly, follows the supercritical pitchfork bifurcation theory: (1) Three flow patterns are all persistent and recurrent, they can be regarded as three flow equilibria; (2) If TSI is below the critical value 1360.9 Wm-2, the positive and negative anomalies are preferred flow patterns and are equally likely to occur; Otherwise, the neutral-type is the only preferred flow pattern. In this project, aiming to generalize the supercritical pitchfork bifurcation theory, the sufficient and necessary conditions for the impact of an arbitrary forcing factor on the onset and decay of the two persistent anomalous Ural flow patterns, which follows the supercritical pitchfork bifurcation theory, will be investigated. Then, the quantitative relationships between common forcing factors and two persistent anomalous Ural flow patterns will be built via the critical points of bifurcation. This project could provide a theoretical basis for improving the prediction level of persistent anomalous weather and climate events in China.