Two different initialization schemes for tropical cyclone (TC) prediction in numerical models are evaluated based on a case study of Typhoon Lekima (2019). The first is a dynamical initialization (DI) scheme where the axisymmetric TC vortex in the initial conditions is spun up through the 6-h cycle runs before the initial forecast time. The second scheme is a bogussing scheme where the analysis TC vortex is replaced by a synthetic Rankine vortex. Results show that although both initialization schemes can help improve the simulated rapid intensification (RI) of Lekima, the simulation employing the DI scheme (DIS) reproduces better the RI onset and intensification rate than that employing the bogussing scheme (BOG). Further analyses show the cycle runs of DI help establish a realistic TC structure with stronger secondary circulation than those in the control run and BOG, leading to fast vortex spinup and contraction of the radius of maximum wind (RMW). The resultant strong inner-core primary circulation favors precession of the midlevel vortex under the moderate vertical wind shear (VWS) and thus helps vortex alignment, contributing to an earlier RI onset. Afterwards, the decreased vertical shear and the stronger convection inside the RMW support the persistent RI of Lekima in DIS. In contrast, the reduced VWS is not well captured and the inner-core convection is weaker and resides farther away from the TC center in BOG, leading to slower intensification. The results imply that the DI effectively improves the prediction of the inner-core process, which is crucial to the RI forecast.

中文翻译：

---

模拟台风利奇马快速增强的两种初始化方案评估（2019）

基于台风利奇马 (2019) 的案例研究，评估了数值模型中热带气旋 (TC) 预测的两种不同初始化方案。第一个是动态初始化 (DI) 方案，其中初始条件下的轴对称 TC 涡旋在初始预测时间之前通过 6 小时循环运行。第二种方案是一种伪造方案，其中分析 TC 涡流被合成朗肯涡流取代。结果表明，虽然两种初始化方案都可以帮助改善 Lekima 的模拟快速强化 (RI)，但采用 DI 方案 (DIS) 的模拟比采用伪造方案 (BOG) 的模拟再现了更好的 RI 开始和强化率。进一步的分析表明，DI 的循环运行有助于建立一个真实的 TC 结构，其二次环流比控制运行和 BOG 中的更强，导致快速涡旋旋转和最大风半径 (RMW) 的收缩。由此产生的强大内核初级环流有利于中等垂直风切变 (VWS) 下中层涡旋的进动，从而有助于涡旋对齐，从而导致更早的 RI 开始。此后，降低的垂直切变和 RMW 内部更强的对流支持了利奇马在 DIS 中的持续 RI。相比之下，减少的 VWS 没有被很好地捕获，内核对流较弱，并且离 BOG 中的 TC 中心更远，导致增强速度较慢。结果表明 DI 有效地提高了内核过程的预测，