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

主要研究人员将对飓风强度变化进行协调建模和观测研究，这些变化与核心涡动力学、外雨带区域二次风极大值的形成、眼壁更换周期以及外雨带的动力/热力学反馈有关。本研究的两个主要目的是：1)同时研究飓风雨带外和核心内区域的结构（包括动力和热力学）。2)探讨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。雨带是飓风内核外不对称加热的主要来源。这种不对称加热导致局域位涡（PV）特征，这可能反过来被切向风的径向切变“轴对称”。眼壁的动力学随之重构，整体风暴强度随之改变。因此，雨带结构的详细演变与风暴演变密不可分。通过将雨带细分为对流区和层状区来检查雨带的内部结构，其中加热的垂直分布和PV产生模式不同。通过同时观测眼壁和雨带结构，可以发现雨带的PV特征与风暴强度变化有关。在雨带的对流区和层状区产生的PV特征将与雨带中二次风极大值的形成有关。随着次级风极大值的形成，它们将被研究如何加强和轴对称，并最终取代主风眼墙。为了实现目标1)，首席调查员将使用配备多普勒雷达和投下探空仪的飞机。首先，NOAA 3s在1998-2003年飓风季节收集的数据将被分析。优先考虑Fabian（2003）和Isabel(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，但飞行轨迹并没有专门用于拟议研究的目标。因此，对这些风暴的分析将作为设计多飞机飞行计划的基础，致力于满足本研究的具体目标。该飞行计划将被称为雨带和强度变化实验（RAINEX），将涉及两架装备多普勒的NOAA WP-3D飞机和配备国家大气研究中心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年大西洋飓风现场项目的框架内运行，并将与NOAA的科学家进行协调。为了实现目标2)，首席研究人员将使用迈阿密大学的旋涡跟踪、多巢、非流体静力中尺度模型（MM5），结合波浪模型和海洋模型，进行3-7天的整合，以1-2公里网格分辨率显示飓风内核和雨带的演变和精细结构。将寻求模型模拟与机载雷达和落差探空数据的一致性。将对2005年现场项目中调查的案例进行近实时模拟。这项研究将有助于提高对飓风和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.