Mechanisms for Rapid Intensity Changes in Hurricanes

9714253弗兰克美国气象研究计划(USWRP)是一个跨部门活动，旨在开展和实施必要的研究，以改善向国家提供的气象服务。根据这一计划，国家科学基金会、国家海洋和大气管理局(NOAA)、国家航空航天局和海军研究办公室正在联合评估和支持USWRP高度优先的研究。狂风和大雨！与目前可用的分析和模型相比，与登陆飓风相关的飓风的组织规模要小一些。虽然飓风造成的破坏很大程度上是由小规模和快速变化的核心特征造成的，但控制风、对流和相关现象变化的物理机制却知之甚少。然而，越来越多的证据表明，飓风中心观察到的主要变化和不对称性受到可预测的更大规模特征的强烈影响。改进登陆附近飓风结构和强度预报的一个有希望的办法是提高我们对这些因果关系的量化理解。这项研究计划将利用一系列飓风数值模拟来研究登陆前后飓风结构和强度变化的机制。最先进的非静力模式将被用来模拟飓风核心对风速、垂直风切变、大尺度梯度和位涡异常以及边界层过程的变化做出反应时的快速、小范围变化。这项研究的主要重点将是外部环流和地表性质的强加变化如何影响飓风的二级环流，从而调节对流的大小和分布。研究还将分析风暴对流中的不对称性，包括螺旋雨带中的对流，如何影响风暴的强度和核心结构。这些结果应能显著改善对飓风结构快速变化过程的理解，并可立即用于改进对飓风中的风、风暴潮和降雨量的预报。***

9714253 Frank The U.S. Weather Research Program (USWRP) is an interagency activity designed to perform and implement the research necessary to improve the delivery of weather services to the nation. Under this Program, the National Science Foundation, the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration and the Office of Naval Research are jointly evaluating and supporting research of high priority to the USWRP. The intense winds and rainfall! associated with landfalling hurricanes are organized on smaller scales than those that can be forecast using currently available analyses and models. Although much of the damage caused by hurricanes results from small-scale and rapidly changing features of the core, the physical mechanisms governing changes in the winds, convection and related phenomena are poorly understood. There is, however, growing evidence that the major changes and asymmetries observed in the cores of hurricanes are strongly modulated by larger- scale features that can be predicted. A promising approach to improving forecasts of the structure and intensity of hurricanes near landfall is to improve our quantitative understanding of these causal relationships. This research program will study the mechanisms by which hurricane structure and intensity vary near and after landfall using a series of numerical simulations of hurricanes. A state-of-the-art non-hydrostatic model will be used to simulate rapid, small-scale variations in the hurricane core as it responds to imposed variations in wind speed, vertical wind shear, large-scale gradients and anomalies of potential vorticity, and changes in boundary layer processes. A primary focus of the study will be on the manner in which the imposed variations in external circulations and surface properties affect the hurricane's secondary circulation, and hence modulate the magnitude and distribution of convection. The re search will also analyze the manner in which asymmetries in the storm convection, including convection in the spiral rainbands, affect the storm's intensity and core structure. The results should provide significantly improved understanding of the processes governing rapid changes in hurricane structure, and they should be of immediate use in improving forecasts of the winds, storm surge and rainfall in hurricanes. ***