The Effects of Tropical Waves on the Formation and Structure of Tropical Cyclones

大气中的五种大尺度热带波在地球赤道地区周围传播。在他之前的工作中，PI分析了观测中的这些波，并确定五种波类型中的四种对热带气旋(西半球称为飓风)的形成有重大影响。他和其他人最近的研究表明，传播的波在调节降雨和风的模式方面发挥了主要作用。它们还被证明与世界各地发生的许多或大多数热带气旋的形成密切相关。它们几乎肯定也会影响成熟飓风的结构和强度。在这项工作的基础上，该研究项目侧重于确定大规模热带波在北大西洋和东北太平洋盆地飓风形成和调制中的作用。根据这一奖项，PI将重点关注2003-2005年间形成的风暴。最后一年是破坏性北大西洋飓风活跃的一年。观测分析将确定在每个风暴的形成和发展过程中出现了哪些热带波。将寻求不同类型波浪的存在与风暴形成和风暴结构变化之间的关系。每个案例研究将由观测分析和一系列数值模拟实验组成。观测分析将使用频谱过滤技术来隔离风暴整个生命周期中发生的波动扰动场。滤波带将被设计成捕捉在大尺度气流中最突出的五种主要热带波型(Madden-Julian振荡、赤道Rossby波、混合Rossby重力波、开尔文波和热带低压类型波)的活动。这些经过过滤的数据，连同来自现有数据源的飓风结构数据，将被用来确定波浪活动与飓风的形成和结构变化之间的关系。风暴将使用高分辨率版本的天气研究和预报(WRF)模型进行模拟。使用大气的全部观测状态作为初始条件的控制模拟将与不同类型的波已从初始状态中移除或包括在修改的相位或强度中的模拟进行比较。根据这些实验的结果，将定量确定热带波对气旋形成和结构演变的影响。除了提高我们对控制飓风行为的重要物理机制的了解外，这项研究还应该直接提高预测飓风形成和结构变化的能力。要研究的热带波是大范围的，周期约为4-90天。使用统计和/或确定性模型，这些波动本质上是可预测的。了解这些波如何影响热带气旋将有助于改进对热带气旋形成和发展的预测。两名研究生将接受博士级别的培训。

Five types of large-scale tropical waves in the atmosphere travel around Earth's equatorial regions. In his previous work, the PI analyzed these waves in observations and determined that four of the five wave types have a significant influence on the formation of tropical cyclones (called hurricanes in the Western Hemisphere). His and others' recent research have shown that the propagating waves play major roles in modulating patterns of rainfall and winds. They have also been shown to be integrally related to the formation of many or most of the tropical cyclones that occur throughout the world. They almost certainly affect the structure and intensity of mature hurricanes as well. Building upon that work, this research project focuses on determining the role of large-scale tropical waves in forming and modulating hurricanes in the North Atlantic and Northeast Pacific basins. Under this award the PI will focus on storms that formed in the years 2003-2005. The final year was an active year for destructive North Atlantic hurricanes. Observational analyses will determine what tropical waves were present during the formation and development of each storm. Relationships will be sought between the presence of different types of waves and storm formation and changes in storm structure. Each case study will consist of observational analyses and a series of numerical simulation experiments. The observational analyses will use spectral filtering techniques to isolate the wave perturbation fields occurring throughout the storm's life cycle. The filter bands will be designed to capture the activity of the five major tropical wave types that are most prominent in the large-scale flow (the Madden-Julian Oscillation, equatorial Rossby waves, mixed-Rossby-gravity waves, Kelvin waves, and tropical-depression-type waves). These filtered data, along with the hurricane structure data from the available data sources, will be used to determine relationships between wave activity and the formation and structural changes of the hurricanes. The storms will be simulated using a high-resolution version of the Weather Research and Forecasting (WRF) model. Control simulations, using the full observed state of the atmosphere as initial conditions will be compared with simulations in which the different types of waves have been removed from the initial state or included with modified phases or strengths. From the results of these experiments, the influences of tropical waves on cyclone formation and structural evolution will be determined quantitatively. In addition to improving our knowledge of important physical mechanisms governing the behavior of hurricanes, this study should lead to direct improvements in the capacity to forecast hurricane formation and structure change. The tropical waves to be studied are large-scale and have periods ranging from about 4-90 days. These waves are inherently predictable using statistical and/or deterministic models. Understanding how these waves influence tropical cyclones will lead to improved predictions of tropical cyclone formation and development. Two graduate students will be trained at the PhD level.