Easterly Wave-Itcz Interaction and Tropical Cyclone Formation over the Atlantic

大多数大西洋热带气旋，特别是最危险的飓风，都是由大西洋主发展区（MDR：北纬10- 20度，西经20- 80度）上空的东风波发展而成，沿着热带辐合带（ITCZ）的北方边缘。ITCZ轴和波轨之间的紧密接近允许ITCZ波在不同的时间尺度上相互作用。该项目旨在研究ITCZ和大西洋上空东风波之间的相互作用及其相互作用对随后风暴发展的影响。特别是，东风波将被视为大规模环流和热带气旋形成之间的“连接纽带”。该联系的统计方面是相对众所周知的，但动力学和物理机制不是。该项目包括观测分析和数值模拟，重点是ITCZ波相互作用和热带气旋形成的一套可检验的假设。研究人员将利用他们最近开发的有袋动物框架的见解来研究大西洋ITCZ的变化如何通过改变波“袋”的存在和形态来影响大西洋MDR的热带气旋生成。重点讨论了波袋的结构和演化，以及多尺度框架下ITCZ与波的相互作用。波袋是一个区域内的波的临界层近似封闭的拉格朗日环流，我们以前的研究表明，风暴形成的必要条件。这项工作的更广泛影响是促进我们了解大尺度环流对热带气旋形成和变化的影响，最终有助于改进热带气旋预报和研究气候变化中的热带气旋活动。该提案将培养和支持一名研究生。

A large number of Atlantic tropical cyclones, especially the most dangerous hurricanes, develop from easterly waves over the Atlantic Main Development Region (MDR: 10-20N, 20-80W), along the northern edge of the Intertropical Convergence Zone (ITCZ). The close proximity between the ITCZ axis and the wave track allows ITCZ-wave interaction on different time scales. This project aims to study the interaction between the ITCZ and easterly waves over the Atlantic and the impacts of their interaction on subsequent storm development. In particular, easterly waves will be examined as a "connecting link" between the large-scale circulation and tropical cyclone formation. The statistical aspects of the link are relatively well-known, but the dynamical and thermodynamical mechanisms are not. This project consists of observational analysis and numerical modeling that focus on a set of testable hypotheses on ITCZ-wave interaction and tropical cyclone formation. The investigators will use insights from their recently developed marsupial framework to examine how the variability of the Atlantic ITCZ affects tropical cyclogenesis in the Atlantic MDR by altering the existence and morphology of the wave "pouch". The emphases are on the structure and evolution of the wave pouch, and ITCZ-wave interaction in a multi-scale framework. The wave pouch is a region of approximately closed Lagrangian circulation within the wave's critical layer and is shown by our previous studies to be a necessary condition for storm formation. Broader impacts of this work are in advancing our understanding of the impacts of the large-scale circulation on tropical cyclone formation and variability, which can ultimately contribute to improved tropical cyclone forecasts and to studying tropical cyclone activity in a changing climate. The proposal will train and support one graduate student.