Numerical Studies of the Landfalling Characteristics and Dynamics of Hurricanes

准确预测登陆时飓风的路径和强度，可以挽救生命，减少经济损失。目前的预报精度受到数值模式初始条件的较差表示、网格分辨率较低以及模式物理不充分的影响。此外，对控制这些风暴的路径和强度的外部和内部过程的了解也相当有限。这项研究的主要目的是，通过对近期登陆飓风的数值模拟，(A)证明如果结合高网格分辨率、现实的模式初始条件和物理学，可以合理地预测这些风暴的路径、极风和降水结构；以及(B)研究登陆前、登陆期间和登陆后的基本物理和动力学过程。这些目标与美国天气研究计划飓风登陆研究计划的目标是相辅相成的。为了实现上述目标，将对两个典型的登陆飓风进行为期5天的云分辨模拟，并加入更现实的初始条件和改进的物理方案。将对模拟结果进行分析，以解决以下问题：在最先进的模型下，观测到的轨迹、强度和强度变化率以及降水在多大程度上可以真实再现？飓风在从海上移动到陆地时有哪些登陆特征？大尺度流动、云微物理、边界层过程和地面条件在决定飓风登陆特征方面的作用是什么？涡旋Rossby波和重力惯性波在螺旋雨带和眼壁对流发展中的相对意义是什么？这项研究的成功完成将有助于支持培养一名博士后研究员和一名研究生。它还将使人们更好地了解飓风的登陆特征，包括核心结构的变化及其基本的动力和物理过程。这项研究将有助于改进对登陆飓风及其相关的极端风和洪水降雨事件的预测，这些事件对美国沿海地区的社会和环境造成了毁灭性的影响。

Accurate forecasts of the track and intensity of hurricanes at landfall can save lives and reduce economic losses. Current forecast accuracy suffers from poor representation of numerical model initial conditions, coarse grid resolution, and inadequate model physics. In addition, understanding of the external and internal processes controlling the track and intensity of these storms is rather limited. The main objectives of this research are, through numerical simulations of recent landfalling hurricanes, to (a) demonstrate that the tracks, extreme winds and precipitation structures of these storms can be reasonably predicted if high grid resolution, realistic model initial conditions and physics are incorporated; and (b) study the underlying physical and dynamical processes prior to, during and after landfall. These objectives are complementary to the goals of the U.S. Weather Research Program Hurricane Landfall research thrust.To achieve the above objectives, 5-day cloud-resolving simulations of two typical landfalling hurricanes will be performed, with the incorporation of more realistic initial conditions and improved physics schemes. The simulation results will be analyzed to address the following questions: Given the state-of-art model, to what extent can the observed tracks, intensity and the rates of intensity change, and precipitation be realistically reproduced? What are the landfalling characteristics of hurricanes as they move from sea to land? What are the roles of large-scale flows, cloud microphysics, boundary-layer processes, and surface conditions in determining the landfalling characteristics of hurricanes? What is the relative significance of vortex-Rossby and gravity-inertial waves in the development of spiral rainbands and eyewall convection? Successful completion of this research will help support the training of a postdoctoral researcher and a graduate student. It will also provide a better understanding of the landfalling characteristics of hurricanes, including the inner-core structural changes and their underlying dynamical and physical processes. This research will contribute to the improved prediction of hurricanes at landfall and their associated extreme winds and flooding rainfall events that have devastating effects on the society and environment of the U.S. coastal regions.