Effects of Large-Scale Flow on the Core Structure of Hurricanes

这项研究计划将研究大尺度环流控制大西洋飓风强烈核心区的结构和强度的方式。该项目将专注于诊断，但将包含一个数值建模组件。这项观测研究将使用来自研究机的数据来分析飓风眼壁区域风、雨和涡度分布的对称和非对称特征。数据来源将包括沿飞行路线的现场测量、雷达反射率和多普勒雷达测量，以及落差探测仪数据。Dropwinsonde数据至关重要，因为它们将使分析从核心向外扩展到1000-2000公里半径，在该地区，由于风暴-环境相互作用，流动与全球分析场解析的流动有很大不同。研究的数值模拟部分将主要是试验性工作，将使用具有三重嵌套网格的宾夕法尼亚州立大学NCAR中尺度模式(MM5)的非静力版本。最里面的网格大小为5公里(一些最终运行在3公里)，该网格上的湿对流过程将用显式水汽方案解决。模拟将使用作为研究的观察部分的一部分案例分析的子集数据进行初始化。对飞机和大规模数据的数值模拟和诊断分析的互动使用将使我们能够详细研究大尺度气流与飓风核心的强度和结构之间相互作用的性质。由于随着飓风预报所关注的时间尺度(0-5天)，大尺度气流的预测越来越准确，确定大尺度气流控制风、雨和相关现象在核心的强度和分布的方式应有助于提高这些重要数量的可预测性。

This research program will examine the manner in which large-scale circulations control thc structure and intensity of the intense core regions of Atlantic hurricanes. The project will focus on diagnostics, but will contain a numerical modeling component. The observational study will use data from research aircraft to analyze symmetric and asymmetric features of the distributions of wind, rain and vorticity in the hurricane eyewall region. Data sources will include in-situ measurements along the flight path, radar reflectivity and Doppler radar measurements, and dropwinsonde data. The dropwinsonde data are crucial as they will allow the analyses to be extended outward from the core to 1,000-2,000 km radius, a region in which the flow differs significantly from that resolved by global analysis fields due to storm-environmental interactions.The numerical modeling portion of the study will primarily be a pilot effort and will use the nonhydrostatic version of the Penn State NCAR Mesoscale Model (MM5) with triply nested grids. The innermost mesh size will be 5 km (with some final runs at 3 km), and moist convective processes on this mesh will be resolved with the explicit moisture scheme. The simulations will be initialized with data from a subset of the cases analyzed as part of the observational component of the study. The interactive use of numerical simulations and diagnostic analyses of aircraft and large-scale data will allow detailed study of the nature of interactions between the large-scale flow and the intensity and structure of the hurricane's core. Since the large-scale flow is becoming increasingly well predicted over time scales of interest to hurricane forecasting (0-5 days), determining the manner in which the large-scale flow controls the intensity and the distribution of wind, rain and related phenomena in the core should lead to improved predictability of these important quantities.