Phenomena and Mechanisms of Wavenumber-2 Structure Excitation in Tropical Cyclones by the Kuroshio Temperature Front in the East China Sea

本文利用全球降水计划(Global precipitation measurement, GPM)降水数据以及中国气象局发布的西北太平洋热带气旋最佳路径集等数据，分析了0515号台风“卡努”经过黑潮海洋锋时的结构变化，并利用WRF模式进行数值模拟，初步分析了其中的物理机制。结果显示，卡努穿越黑潮的过程中，下垫面黑潮海洋锋强度较强，海面向卡努提供强烈的非对称非绝热加热，通过傅里叶谐波分解计算发现该加热以二波分量占据主导地位，这会使得卡努切向的二波分量活动增强，与其相关的位涡扰动在激发对流以后，黑潮提供的有利条件会进一步促进位涡扰动和对流的发展，导致二波结构的增强，形成两个较强的降水对流中心，最终使得卡努产生更严重的危害性。This study investigates the structural changes of Typhoon Khanun (0515) as it traversed the Kuroshio front, utilizing precipitation data from the Global Precipitation Measurement (GPM) mission and the best-track dataset of tropical cyclones in the Northwest Pacific issued by the China Meteorological Administration. Numerical simulations were conducted using the Weather Research and Forecasting (WRF) model to preliminarily analyze the underlying physical mechanisms. The results reveal that during Khanun's passage over the Kuroshio front, the strong sea surface temperature gradient of the Kuroshio provided intense asymmetric diabatic heating to the typhoon. Fourier harmonic decomposition indicates that the heating was dominated by the wavenumber-2 component, which enhanced the tangential wavenumber-2 activity of Khanun. The associated potential vorticity perturbations, upon triggering convection, were further amplified by the favorable conditions provided by the Kuroshio, leading to the intensification of the wavenumber-2 structure. This process resulted in the formation of two strong convective precipitation centers, ultimately increasing the destructive potential of Typhoon Khanun.