Mechanisms for Rapid Intensity Changes in Hurricanes

更好地预测飓风强度的问题已被美国天气研究计划确定为一个高度优先的研究领域。当飓风接近登陆时，飓风中强风的水平分布往往变得高度不对称，眼壁和雨带中的强烈对流也是如此。强烈的中尺度涡旋，小到几公里的尺度，被认为在强烈的登陆飓风中造成重大破坏。本项目旨在利用全物理、高分辨率的先进数值模拟系统，分析热带气旋与环境垂直风切变相互作用的物理机制。先前的研究表明，持续和可预测的对流不对称是对施加的环境垂直风切变的响应。通过更好地了解在热带气旋对流中产生不对称的过程，以及通过了解这些不对称如何反馈到热带气旋的强度和结构，改进这些事件的预测应该是可能的。特别令人感兴趣的是在与瞬态环流引起的垂直风切变相互作用过程中飓风核心对流的不对称发展。当垂直风切变被施加到飓风核上时，不对称将会发展，这种不对称可以被恒切变研究很好地预测。然而，随着风切变的消退，将研究飓风核心结构变化的时间演化，特别是它们对风暴强度变化的反馈。本研究旨在通过检查一系列初始值和时变的全物理模拟，利用非常精细的网格和明确的潮湿物理来实现这些过程的知识。综合研究结果，建立一系列核心强度变化的因果关系，并通过实际数据案例对这些关系进行检验。这项研究的成功完成可能会导致飓风登陆预报的改进。

The problem of better forecasting of the intensity of hurricanes has been identified by the U.S. Weather Research Program as a high priority research area. As hurricanes approach landfall, the horizontal distribution of intense winds in hurricanes often becomes highly asymmetrical, as does the intense convection in the eyewall and rainbands. Intense mesoscale vortices, as small as a few kilometers in scale, are believed to produce major damage in intense landfalling hurricanes. This project aims to analyze the physical mechanisms associated with interaction of a tropical cyclone with environmental vertical wind shear using a full-physics, high resolution advanced numerical modeling system. Previous studies have shown that persistent and predictable convective asymmetries develop in response to imposed environmental vertical wind shear. By better understanding the processes that produce asymmetries in tropical cyclone convection, and by understanding how those asymmetries feed back on the tropical cyclone intensity and structure, improved prediction of these events should be possible. Of particular interest is the development of asymmetries in the hurricane core convection during interaction with vertical wind shear caused by transient circulations. As the vertical wind shear is imposed on the hurricane core, asymmetries should develop that are well predicted by the constant-shear studies. However, as the wind shear recedes, the time-evolution of the core structural changes in the hurricane will be studied, particularly as they feed back on changes in the storm intensity. This study seeks to achieve knowledge of these processes through examination of a series of initial-value and time varying, full-physics simulations utilizing a very fine mesh and explicit moist physics. The results will be synthesized to establish a series of cause and effect relationships governing core intensity changes, and these relationships will be tested by examining real-data cases.Successful completion of this research potentially will lead to improvements in the forecasting of landfalling hurricanes.