美国夏威夷马诺大学Yuqing Wang课题组报道了热带气旋增强的最佳初始内核大小。相关论文发表在2024年4月10日出版的《大气科学进展》杂志上。

据了解，最近的观测和数值研究揭示了热带气旋(TC)的增强速率与内核大小的相关性。

本研究使用两种不同数值模型的理想化模拟，初始内核大小(即最大风半径-RMW)在20-180km之间变化，研究发现，寿命最大强化率(LMIR)与内核大小存在非单调相关关系。也就是说，对于TC的LMIR存在一个最优的内核大小。切向风收支分析表明，与大型TC相比，小型TC由于RMW内部绝对涡度较大，而具有较大的绝对涡度内通量。然而，小型TC也受到穿过眼壁的强横向扩散的影响，这在一定程度上抵消了绝对涡度向内大通量的积极贡献。

这两个相互竞争的过程最终导致具有中等初始内核大小的TC具有最大的LMIR。灵敏度试验结果表明，最佳大小在40-120km范围内变化，随海温升高、纬度降低、水平混合长度增大、初始TC强度减弱而增加。40-120km的RMW与观测中最常见的TC增强的内核大小相对应，表明TC增强的初始大小是自然选择的。本研究强调了通过数值天气预报模式准确表征TC内核大小对预测TC强度的重要性。

附：英文原文

Title: On the optimal initial inner-core size for tropical cyclone intensification: An idealized numerical study

Author: Rong FEI, Yuqing Wang

Issue&Volume: 2024-04-10

Abstract: Recent observational and numerical studies have revealed the dependence of the intensification rate on the inner-core size of tropical cyclones (TC). In this study, with the initial inner-core size (i.e., the radius of maximum wind—RMW) varied from 20–180 km in idealized simulations using two different numerical models, we found a nonmonotonic dependence of the lifetime maximum intensification rate (LMIR) on the inner-core size. Namely, there is an optimal inner-core size for the LMIR of a TC. Tangential wind budget analysis shows that compared to large TCs, small TCs have large inward flux of absolute vorticity due to large absolute vorticity inside the RMW. However, small TCs also suffer from strong lateral diffusion across the eyewall, which partly offsets the positive contribution from large inward flux of absolute vorticity. These two competing processes ultimately lead to the TC with an intermediate initial inner-core size having the largest LMIR. Results from sensitivity experiments show that the optimal size varies in the range of 40–120 km and increases with higher sea surface temperature, lower latitude, larger horizontal mixing length, and weaker initial TC intensity. The 40–120 km RMW corresponds to the inner-core size most commonly found for intensifying TCs in observations, suggesting the natural selection of initial TC size for intensification. This study highlights the importance of accurate representation of TC inner-core size to TC intensity forecast by numerical weather prediction models.

DOI: 10.1007/s00376-024-3296-6

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-3296-6viewType=HTML