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

快速加强(RI)是热带气旋(TC)最不为人所知的阶段之一，它涉及到核心动力与大尺度环境的相互作用以及不同时空尺度之间的相互作用。以往的研究已经表明，对流层上层暖核的快速形成是热带气旋RI爆发的关键。在这项研究中，将通过理想化的和真实的模拟以及使用云解析模式的诊断和预算分析来探索导致TCS中上对流层暖核快速形成的过程。具体而言，将讨论以下三个科学问题：1)在有利的热带海洋条件下，热带气旋的增强速率是由外部还是内部决定的，环境气流或天气尺度强迫是否可以增加没有这些强迫的气旋的增强速率？2)气旋的三维(3D)结构(包括大小)和强度如何决定对流层上部变暖的效率，从而决定气旋本身的增强速率？3)对流爆发和热塔是如何触发的，它们是如何导致风暴核心上方的对流层变暖的？为了回答这些问题，我们将使用PI开发的TC模式(TCM4)和国家大气研究中心(NCAR)开发的高级天气研究和预报(WRF)模式来进行一系列理想化和实况模拟，并进行诊断和预算分析，以验证我们的假设，确定造成RI的物理机制。智力价值：这项研究的结果将提高我们对热带气旋RI的动力学和决定热带气旋潜在增强率的因素的理解。这将有助于提高预测热带气旋强度变化的能力。这项研究的结果还将证明，初始热带气旋的三维结构参数对数值模式的强度预报至关重要，从而有可能改善对热带气旋结构和强度的预报。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TC动力学和建模领域的培训。

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.