Toward Improved Understanding of Rapid Intensification (RI) of Tropical Cyclones

热带气旋的快速强化（RI）过程涉及到热带气旋内部动力与大尺度环境以及不同时空尺度之间的相互作用，是目前人们对热带气旋认识最少的阶段之一。先前的研究已经表明，对流层上层热核的快速形成是一个TC的RI开始的关键。在本研究中，将通过使用云分辨模式的理想和实际模拟以及诊断和预算分析来探索导致tc对流层上层暖核快速形成的过程。具体而言，将解决以下三个科学问题：1)在有利的热带海洋条件下，TC的增强速率是由外部还是内部决定的，以及环境流或天气尺度强迫是否可以增加TC在没有这些强迫的情况下可能具有的增强速率？2) TC涡旋的三维结构（包括大小）和强度如何决定对流层上层变暖的效率，从而决定TC本身的增强速率？3)对流爆发和热塔是如何被触发的，它们又是如何在国际扶轮之前和期间导致风暴核心上方对流层变暖的？为了回答这些问题，我们将使用由PI开发的TC模型（TCM4）和国家大气研究中心（NCAR）开发的先进天气研究和预报（WRF）模型进行一系列理想化和真实情况的模拟，并进行诊断和预算分析，以验证我们的假设，确定负责RI的物理机制。知识价值：这项研究的结果将提高我们对热带气旋强度的动力学和决定热带气旋潜在增强率的因素的理解。更广泛的影响：这项研究将产生一套参数/因素，以决定热带气旋的潜在增强率。这将有助于提高预测TC强度变化的能力。本研究的结果也将证明初始TC三维结构的哪些参数对数值模型的强度预测至关重要，从而有可能改善TC结构和强度的预测。在这个项目的过程中，一名女研究生将接受TC科学方面的培训，特别是在TC动力学和建模领域。

The rapid intensification (RI), which involves interactions between the inner core dynamics and the large-scale environment and among different spatial and temporal scales, is still one of the least understood phases of a tropical cyclone (TC). Previous studies have already shown that the rapid formation of a warm core in the upper troposphere is the key to the RI onset of a TC. In this study, processes that lead to the rapid formation of the upper-tropospheric warm core in TCs will be explored through on idealized and real-case simulations and diagnostic and budget analyses using cloud-resolving models. In particular, the following three scientific questions will be addressed:1) Given favorable tropical ocean conditions, is the intensification rate of a TC externally or internally determined and can an environmental flow or synoptic-scale forcing increase the intensification rate that a TC could have without these forcing?2) How do the three-dimensional (3D) structure (including the size) and intensity of a TC vortex determine the efficiency of the upper-tropospheric warming and thus the intensification rate of the TC itself?3) How are convective bursts and hot towers triggered and how do they lead to the upper tropospheric warming over the storm core prior to and during the RI?To answer these questions, we will use the TC model (TCM4) developed by the PI and the advanced Weather Research and Forecasting (WRF) model developed at National Center for Atmospheric Research (NCAR) to conduct a series of idealized and real-case simulations and perform diagnostic and budget analyses to verify our hypotheses, identify the physical mechanisms responsible for the RI. Intellectual Merit:Results from this research will improve our understanding of the dynamics of the RI of tropical cyclones and factors that determine the potential intensification rate of a TC.Broader Impacts:The research will lead to a set of parameters/factors that determine the potential intensification rate of tropical cyclones. This will contribute to improved ability to predict TC intensity change. Results from this research will also demonstrate what parameters of the three-dimensional structure of the initial TC are critical to the intensity prediction by numerical models, thus potentially leading to improved prediction of TC structure and intensity. In the course of this project, a female graduate student will receive training in the science of TCs, especially in the area of TC dynamics and modeling.