Examining the Dynamics of Rainbands and Secondary Eyewall Formation in Tropical Cyclones

飓风的大小和强度会受到风暴内核变化的影响。 其中一个显著的变化是次生眼壁的发展。 尽管次级眼墙的重要性，但关于它们如何发展以及它们与飓风雨带的相互作用存在着相互竞争的理论。 该项目将利用飓风侦察机的观测结果和最新的数值模拟技术，填补对热带气旋演变的科学认识方面的一个关键空白。 该奖项的主要社会影响将是通过改进热带气旋预报，特别是在登陆前的关键时刻。 该项目还将有助于培养下一代科学家。研究小组计划研究热带气旋内核雨带转变为次级眼墙背后的动力学。 研究人员认为，目前关于次级眼壁形成（SEF）的理论并不能解释连接雨带和SEF的确切动力学路径。 为了在这一课题上取得进展，研究小组将把联合收割机观测分析和数值模拟结合起来。 观测分析将包括过去20年来NOAA P-3飓风猎人飞机对总共38次SEF事件进行的良好采样的数据。 建模方面将集中在最近的事件，如哈维，厄玛和玛丽亚，利用宾夕法尼亚州天气研究预测-EncanteKalman滤波器（WRF-EnKF）系统。 该项目的主要目标是： (1)识别和表征观测中出现在次级眼壁形成之前的相干雨带特征，并与没有形成次级眼壁的风暴中的雨带进行比较，（2）在真实情况模式模拟中检查导致次级眼壁形成的雨带特征，并与观测中的雨带特征进行比较，（三）、通过系统的集合敏感性实验，探索雨带动力学的普遍性和可预测性，从而导致次级眼墙。该奖项反映了NSF的法定使命，并被认为是值得的。通过使用基金会的知识价值和更广泛的影响审查标准进行评估来提供支持。

Hurricane size and intensity can be affected by changes in the inner core of a storm. One of the dramatic changes is the development of a secondary eyewall. Despite the importance of the secondary eyewall, competing theories exist regarding how they develop and their interactions with hurricane rainbands. This project will use a combination of observations from hurricane reconnaissance aircraft and the latest in numerical modeling to fill a critical gap in scientific understanding of tropical cyclone evolution. The main societal impact from the award would be through improved tropical cyclone forecasts, especially in the crucial hours before landfall. The project will also help to train the next generation of scientists.The research team plans to study the dynamics behind the transition of tropical cyclone inner core rainbands into a secondary eyewall. The researchers contend that current theories for secondary eyewall formation (SEF) do not explain the exact dynamical pathway that connects rainbands to SEF. To make progress on this topic, the team will combine observational analysis and numerical modeling. The observational analysis will include data from a total of 38 SEF events that were well sampled by the NOAA P-3 Hurricane Hunter aircraft over the past two decades. The modeling aspect will focus on more recent events, such as Harvey, Irma, and Maria, making use of the Penn State Weather Research Forecasting - Ensemble Kalman Filter (WRF-EnKF) system. The main objectives of the project are to: (1) Identify and characterize coherent rainband features that occurred in observations prior to secondary eyewall formation and compare to those rainbands in storms that did not develop secondary eyewalls, (2) Examine the rainband features leading to secondary eyewall formation in real-case model simulations and compare to those in observations, (3) Explore the ubiquity and predictability of rainband dynamics that lead to secondary eyewalls through systematic ensemble sensitivity experiments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.