基于CMIP6/HighResMIP的西北太平洋热带气旋路径分型及其向极迁移贡献

Track Classification and Contributions to Poleward Migration of Western North Pacific Tropical Cyclones Based on CMIP6/HighResMIP

摘要: 本研究基于1977~2023年西北太平洋热带气旋最佳路径资料，利用质心坐标、路径方差、生成消亡位置及转向角度等多特征进行K-means聚类，将热带气旋路径客观划分为远海转向型、近海西行型、近海转向型、偏东北型和远海西行型五类。通过对比三套CMIP6/HighResMIP模式在历史与未来情景下的模拟结果，揭示了热带气旋向极迁移趋势具有显著的路径依赖性与非均匀特征。结果显示，未来偏东北型与远海西行型路径的最大强度纬度与质心纬度呈现最显著的北移趋势，两类转向型路径的系统性北移对整体向极迁移具有“放大器”效应，而近海西行型路径趋势不确定性最强，多数指标对向极迁移呈负贡献。物理机制分析表明，全球变暖背景下经向温度梯度减弱导致Hadley环流向极扩张、强度减弱，其上升支北移为副热带地区创造了更利于热带气旋生成的动力环境；同时Hadley环流下沉支北扩与副热带高压“北抬西伸”耦合，引导气流带及转向点相应北移，共同驱动了热带气旋路径的向极迁移。

Abstract: Based on the best track data of tropical cyclones (TCs) in the western North Pacific from 1977 to 2023, this study employs a K-means clustering method using multiple features—including centroid positions, track variance, genesis/lysis positions, and turning angles—to objectively classify TC tracks into five types: offshore recurring (OR), nearshore westward (NW), nearshore recurring (NR), northeastward (NE), and offshore westward (OW). By comparing simulations from three CMIP6/HighResMIP models under historical and future scenarios, we reveal that the poleward migration trend of TCs exhibits significant track dependence and non-uniform characteristics. The results show that NE and OW tracks display the most pronounced northward shift in latitude of maximum intensity and centroid latitude under future scenarios. The systematic northward migration of the two recurring types (OR and NR) acts as an “amplifier” for the overall poleward shift, whereas the NW track type shows the strongest uncertainty, with most of its indicators contributing negatively to poleward migration. Physical mechanism analysis indicates that under global warming, the weakened meridional temperature gradient leads to the poleward expansion and overall weakening of the Hadley circulation. The northward shift of its ascending branch creates a more favorable dynamic environment for TC genesis in subtropical regions. Meanwhile, the northward expansion of the descending branch couples with the “northward extension and westward expansion” of the subtropical high, resulting in a corresponding northward displacement of the steering flow and recurvature points, which jointly drive the poleward migration of TC tracks.