论文标题
通过聚集初始强度和内部核心大小来重新访问热带气旋的快速加强定义
Revisiting the definition of rapid intensification of tropical cyclones by clustering the initial intensity and inner-core size
论文作者
论文摘要
热带气旋（TC）的快速强化（RI）在操作预测方面带来了巨大的挑战，并为主要TC的发展做出了重大贡献。 RI通常定义为在24小时内超出一定阈值的最大持续地表风速的增加。使用最广泛的阈值是30 kt（15.4 m/s），这是统计确定的。在这里，我们通过使用最大风速的强度，初始强度和半径对RI提出了一个新的RI定义。一组770个样品以45 kt（23.2 m/s）的阈值分离。北大西洋西部的阈值为40 kt（20.6 m/s），其中TC尺寸测量更可靠。蒙特卡洛实验表明，即使考虑到RMW的不确定性高达30 km，提议的阈值也是可靠的。我们表明，当TC经历RI时，其最大风速约为60 +/- 15 kt（30.9 +/- 7.7 m/s），最大风速的半径为45 +/- 20 km。新的阈值胜过（1）中30 kt/24h的常规阈值，描述了寿命最大强度的双峰分布，以及（2）解释5类TC的年度计数。这个新定义提供了一个更基于物理的阈值，并描述了极端事件的更可靠的表示。尽管需要更多的比较来进行操作应用，但对于基于过程的案例研究来说可能是理想的，并且可以为TC强化分类和研究提供更有价值的指标。
Rapid intensification (RI) of tropical cyclones (TCs) provides a great challenge in operational forecasting and contributes significantly to the development of major TCs. RI is commonly defined as an increase in the maximum sustained surface wind speed beyond a certain threshold within 24 h. The most widely used threshold is 30 kt (15.4 m/s), which was determined statistically. Here we propose a new definition for RI by objectively clustering TCs using the intensification rate, initial intensity, and radius of the maximum wind speed. A group of 770 samples is separated at a threshold of 45 kt (23.2 m/s). The threshold is 40 kt (20.6 m/s) for the western North Atlantic, where TC size measurements are more reliable. Monte Carlo experiments demonstrate that the proposed threshold is robust even considering the uncertainty in RMW of as high as 30 km. We show that, when a TC undergoes RI, its maximum wind speed is approximately 60+/-15 kt (30.9+/-7.7 m/s) and the radius of the maximum wind speed is 45+/-20 km. The new threshold outperforms the conventional threshold of 30 kt/24h in (1) describing the bimodal distribution of lifetime maximum intensity, and (2) explaining the annual count of Category 5 TCs. This new definition provides a more physically-based threshold and describes a more reliable representation to the extreme events. Although more comparisons are needed for operational application, it is likely to be desirable for process-based case studies, and could provide a more valuable metric for TC intensification classification and research.
