Study of Processes Leading to Tropical Cyclone Intensity Change

美国天气研究计划(USWRP)的主要研究领域之一是进行必要的研究，以改进热带气旋(TC)的路径和强度预报。这项研究的主要目标是了解导致热带气旋强度变化的过程。虽然热带气旋强度变化有多个过程，但PI将集中在内核区(距离气旋中心约150公里范围内)发生的过程，包括内外螺旋雨带的相互作用、眼壁对流、涡旋Rossby波和眼壁破裂过程。工作假设是，任何外部强迫对热带气旋强度的影响都是直接或间接地通过内核区的中尺度过程发生的。将讨论以下科学问题：a.在没有任何环境气流的外部强迫的情况下，内部核心区内部产生的不对称结构如何与对称涡旋相互作用并影响TC强度？B.外部螺旋雨带是如何形成的，为什么它们最常在距TC中心80~150公里之间形成，它们是如何传播并与内部螺旋雨带和眼壁对流相互作用，影响TC强度的？C.眼壁如何对外部强迫做出反应，例如环境水流中的垂直切变，这种反应的后果是什么？为了回答这些问题，PI将使用由首席调查员开发的完全可压缩、非静力、三维多重嵌套、可移动网格、高分辨率模式(TCM4)进行理想化的数值模拟。将对数值结果进行综合诊断，以阐明物理机制。这项研究的更广泛影响包括改进了对影响热带气旋结构和强度变化的物理过程的了解，从而改进了对热带气旋结构和强度变化的预测，特别是通过数值天气预测模型。特别是，这项研究的结果将讨论内核不对称动力及其对外部强迫的响应在导致热带气旋强度变化方面的可能作用。这项工作的教育效益包括培养研究生。这项研究在USWRP中具有高度优先地位。

One of the primary research areas under the U.S. Weather Research Program (USWRP) is to perform the research necessary to improve track and intensity forecasts of tropical cyclones (TC). The major goal of this research is to understand the processes that lead to intensity changes in tropical cyclones. While there are many processes responsible for tropical cyclone intensity change, the PI will focus on those occurring in the inner core region (within about 150 km from the cyclone center), including interactions between inner and outer spiral rainbands, eyewall convection; vortex Rossby waves, and eyewall breakdown process. The working hypothesis is that the effect of any external forcing on TC intensity occurs either directly or indirectly through mesoscale processes in the inner core region. The following scientific questions will be addressed: a. How does the internally generated asymmetric structure in the inner core region interact with the symmetric vortex and affect the TC intensity even without any external forcing from environmental flow? b. How do the outer spiral rainbands form, why they most frequently form between 80 km and 150 km from the TC center, and how do they propagate and interact with the inner spiral rainbands and eyewall convection, affecting the TC intensity? c. How does the eyewall respond to external forcing, such as that from vertical shear in the environmental flow, and what is the consequence of this response? To answer these questions, the PI will perform idealized numerical simulations using a fully compressible, nonhydrostatic, three-dimensional multiply nested, movable mesh, high-resolution model (TCM4) developed by the Principal Investigator. Comprehensive diagnostics of the numerical results will be performed to elucidate the physical mechanisms. The broader impacts of the research include the improved understanding of the physical processes that affect the tropical cyclone structure and intensity changes, leading to improved prediction of tropical cyclone structure and intensity change, especially by numerical weather prediction models. In particular, results from this research will address the possible role of inner core asymmetric dynamics and their response to external forcing in causing the intensity change of tropical cyclones. Educational benefits of the work include the training of graduate students. This research is of high priority within the USWRP.