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

本研究项目将研究大尺度环流如何控制大西洋飓风强核心区的结构和强度。该项目将侧重于诊断，但将包含一个数值模拟组件。观测研究将使用研究飞机的数据来分析飓风眼壁区域风、雨和涡度分布的对称和不对称特征。数据来源将包括沿飞行路径的原位测量，雷达反射率和多普勒雷达测量，以及dropwinsonde数据。dropwinsonde数据至关重要，因为它们将允许分析从核心向外扩展到半径1,000-2,000公里的区域，由于风暴与环境的相互作用，该区域的流量与全球分析场所解决的流量有很大不同。该研究的数值模拟部分将主要是试点工作，将使用宾夕法尼亚州立大学NCAR中尺度模型（MM5）的非流体静力版本，具有三重嵌套网格。最内层网格尺寸为5公里（最终运行为3公里），该网格上的湿对流过程将用显式湿度方案来解决。模拟将使用作为研究观测部分的一部分所分析的案例子集的数据进行初始化。数值模拟和飞机诊断分析以及大尺度数据的交互使用将允许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本质。由于大尺度气流对飓风预报（0-5天）的时间尺度的预测越来越好，确定大尺度气流控制核心风、雨和相关现象的强度和分布的方式应该会提高这些重要量的可预测性。

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.