AI 中文总结
该研究通过对ERA5再分析数据的西北太平洋热带气旋温度异常场做EOF分析，构建热相空间，实现了对热带气旋热结构与强度演变的客观诊断，为相关理论研究和业务预报提供了新工具。
AI 中文摘要
当前对热带气旋（TC）暖核的认识主要依赖探空和卫星产品的统计平均结果，这些结果提供的是气候态热状态，无法充分刻画暖核在整个TC生命周期内的连续三维演变特征。本研究对1979-2024年ERA5再分析数据集得到的西北太平洋（WNP）TC三维温度异常场，应用经验正交函数（EOF）分析。研究发现，前三个EOF模态有效捕捉了TC热结构的主要特征：第一模态代表典型暖核结构，第二模态表征垂直斜压性，第三模态捕捉温度异常的水平不对称性。利用前三个主成分（PCs），我们构建了三维笛卡尔坐标系，在此框架内，两个相参数定义了热相空间，用于可视化TC的三维热结构：一个参数诊断垂直正压或斜压结构，另一个量化热场的水平不对称性。结果表明，相图中的轨迹可有效捕捉观测到的强度变化和热结构演变。基于EOF的相图通过量化关键热特征及其与TC强度的动态关系，为分析和诊断结构热力学特征及强度演变提供了有前景的见解和新颖、客观的工具，这种能力有望极大推动TC的理论认识和业务预报工作。
英文摘要
Current understandings of the tropical cyclone (TC) warm core primarily relies on statistical averages from soundings and satellite products, which provide a climatological thermal state but cannot adequately characterize the continuous three-dimensional evolution of the warm core throughout the TC life cycle. In this study, Empirical Orthogonal Function (EOF) analysis was applied to three-dimensional temperature anomalies of Western North Pacific (WNP) TCs derived from the ERA5 reanalysis dataset for the period 1979-2024. We found that the three leading EOF modes effectively capture the primary characteristics of the TC thermal structure: the first mode represents the typical warm core structure; the second mode characterizes vertical baroclinicity; and the third pattern captures the horizontal asymmetry of the temperature anomalies. Using the first three principal components (PCs), we established a three-dimensional Cartesian coordinate system. Within this framework, two phase parameters define a thermal phase space to visualize the TC's three-dimensional thermal structure: one diagnoses the vertical barotropic or baroclinic structure, and the other quantifies the horizontal asymmetry of the thermal field. The results demonstrate that the trajectory in the phase diagram effectively captures the observed intensity changes and thermal structural evolution. The EOF-based phase diagrams offer promising insights and provide a novel, objective tool for analyzing and diagnosing structural thermodynamic characteristics and intensity evolution by quantifying key thermal features and their dynamic relationships with TC intensity. This capability thereby holds substantial potential for advancing both theoretical understanding and operational forecasting of TCs.
