Collaborative Research: Observational and Modeling Study of Hurricane Rainbands and Intensity Changes

首席调查员将对飓风强度的变化进行协调模拟和观测研究，这些变化与内部核心涡旋动力学、外部雨带区域次生最大风速的形成、眼壁更换周期以及外部雨带的动力/热力学反馈有关。这项研究的两个主要目的是：1)同时检查飓风外部雨带和核心区域的结构(动力和热力学)。2)研究雨带与初级飓风涡旋环流的相互作用及其在飓风强度变化中的作用。雨带是飓风核心外不对称加热的主要来源。这种不对称的加热导致局部位涡(PV)特征，而这些特征又可能被切向风的径向切变“轴对称”。然后对眼壁动态进行重组，并更改总体风暴强度。因此，雨带结构的详细演变与风暴演变密不可分。雨带的内部结构将通过将雨带细分为对流区和层状区来检查，在这些区域中，热量的垂直分布以及光伏的产生模式是不同的。通过同时检查眼壁和雨带结构，雨带的PV特征可以与风暴强度的变化联系起来。在雨带的对流和层状区产生的PV特征将与雨带中二次风极大值的形成有关。随着二次风极大的形成，人们将研究它们如何加强和轴对称，并最终成为主要眼壁。针对目标1)，首席调查员将使用配备了多普勒雷达和空投探测仪的飞机。首先，将分析美国国家海洋和大气局P3在1998-2003年飓风季节收集的数据。将优先考虑法比安(2003)和伊莎贝尔(2003)，他们展示了明确的眼壁、雨带和眼壁更换周期。虽然在这些风暴中收集了机载多普勒雷达数据，但飞行轨迹并不是针对拟议研究的目标。因此，对这些风暴的分析将成为设计多飞机飞行计划的基础，以满足本研究的具体目标。这项飞行计划将被称为雨带和强度变化实验(RAINEX)，将包括两架配备多普勒的NOAA WP-3D飞机以及配备有国家大气研究中心Eldora多普勒系统的NRL P3。RAINEX将在美国国家海洋和大气管理局(NOAA)2005年大西洋飓风场计划的背景下运行，并将与NOAA的科学家协调。为了满足目标2)，首席调查人员将使用迈阿密大学的涡旋跟踪、多嵌套、非静力中尺度模式(MM5)以及波浪模式和海洋模式进行为期3-7天的积分，以1-2公里网格分辨率显示飓风核心和雨带的演变和精细结构。将寻求模型模拟与机载雷达和空投探空仪数据的一致性。将对2005年外地方案中调查的案件进行近乎实时的模拟。这项研究将有助于提高对飓风及相关极端风和山洪事件的预测，这些事件对美国沿海地区的生命和财产造成毁灭性影响。

The Principal Investigators will perform a coordinated modeling and observational study of hurricane intensity changes in relation to inner-core vortex dynamics, formation of secondary wind maxima in the outer rainband region, eyewall replacement cycles, and dynamic/thermodynamic feedbacks of outer rainbands. The two main objectives of this study are: 1) To examine structures (both dynamic and thermodynamic) of hurricane outer rainband and inner core regions simultaneously. 2) To investigate the interactions of the rainbands and primary hurricane vortex circulation and the role of these interactions in hurricane intensity changes. Rainbands are major sources of asymmetric heating outside of the hurricane inner core. This asymmetric heating leads to localized potential vorticity (PV) features, which may in turn be "axisymmetrized" by the radial shear of the tangential wind. The eyewall dynamics are then restructured and the overall storm intensity changes. Thus, the detailed evolution of the structure of the rainbands is integrally involved in storm evolution. The internal structure of the rainbands will be examined by subdividing the bands into convective and stratiform regions where the vertical distributions of heating and thus PV generation patterns are different. By simultaneously examining the eyewall and rainband structures, the PV features of the rainbands can be related to storm intensity changes. The PV features generated in the convective and stratiform regions of rainbands will be examined in relation to the formation of secondary wind maxima in the rainbands. As the secondary wind maxima take shape, they will be examined for how they may intensify and axisymmetrize and eventually take over as the main eyewall. To address objective 1), the Principal Investigators will use aircraft equipped with Doppler radar and dropsondes. First, data collected by the NOAA P3s during the 1998-2003 hurricane seasons will be analyzed. Priority will be given to Fabian (2003) and Isabel (2003), which exhibited well-defined eyewalls, rainbands, and eyewall replacement cycles. Although airborne Doppler radar data were collected in these storms, the flight tracks were not dedicated to the objectives of the proposed study. The analysis of these storms will, therefore, serve as the foundation for the design of a multi-aircraft flight program dedicated to meet the specific objectives of this research. This flight program will be called the Rainband and Intensity Change Experiment (RAINEX), and will involve the two Doppler equipped NOAA WP-3D aircraft plus the NRL P3 with the National Center for Atmospheric Research ELDORA Doppler system. RAINEX will operate within the context of the National Oceanic and Atmospheric Administration (NOAA) 2005 hurricane field program over the Atlantic and will be coordinated with NOAA scientists.To address objective 2), the Principal Investigators will use the University of Miami's vortex following, multi-nested, non-hydrostatic mesoscale model (MM5) coupled with a wave model and an ocean model to carry out 3-7 day long integrations showing the evolution and fine structures of the hurricane inner-core and rain-bands at 1-2 km grid resolution. Consistency of the model simulations with the airborne radar and dropsonde data will be sought. Near real-time simulations will be done for cases investigated in the 2005 field program. This study will contribute to the societal goal of improving predictions of hurricanes and associated extreme wind and flash flood events that have a devastating impact on life and property in the U. S. coastal regions.