An Investigation of the Dynamic and Thermodynamic Processes that Lead to Distinctly Different Pathways to Tropical Cyclogenesis

热带风暴和飓风的形成，被称为热带气旋形成，是一个复杂的过程，涉及大尺度环境和经过的小尺度大气扰动之间的相互作用。人们已经发展了多种理论，试图描述扰动成为热带风暴的途径。在这个项目中，研究人员将使用先进的、高分辨率的数值模拟来分析这两种途径中涉及的过程。提高对热带气旋形成方式的了解将有助于预报员和改善公共安全，特别是在小风暴发展非常接近人口稠密地区的情况下。该奖项还将为研究生提供培训机会。热带气旋形成的第一个途径的特点是气旋表面风的自旋上升和深对流塔中心涡度的建立。第二种是在大尺度环流中心附近有一个小的表面集中涡，然后是一个中层涡。研究计划是使用区域大气模拟系统（RAMS）和天气研究与预报（WRF）模式进行理想数值实验，其中RAMS采用新的边缘和地表通量格式，WRF采用移动嵌套网格。该项目的主要目标是：1)确定强中层涡旋发展的物理机制和有利于其发生的条件；2)确定导致小表面集中涡旋形成的过程；3)确定垂直风切变（包括平均气流）对热带气旋形成路径的影响。

The formation of tropical storms and hurricanes, known as tropical cyclogenesis, is a complex process involving interactions between the large-scale environment and a smaller-scale atmospheric disturbance passing through. There have been multiple theories developed to try to describe the pathway that a disturbance takes on its road to becoming a tropical storm. In this project, researchers will use advanced, high-resolution numerical modeling to analyze the processes involved in two of these pathways. Improved knowledge of how tropical cyclones form will aid forecasters and improve public safety, especially in the cases where small storms develop very close to populated areas. This award will also provide a training opportunity for a graduate student. The first pathway to tropical cyclogenesis is characterized by a spin up of cyclonic surface winds and vorticity building in the center of deep convective towers. The second is characterized by a mid-level vortex that is followed by a small surface concentrated vortex near the center of the large scale circulation. The research plan is to conduct idealized numerical experiments using the Regional Atmospheric Modeling System (RAMS) with new riming and surface flux schemes and the Weather Research and Forecasting (WRF) model with moving nested grids. The main objectives that the project will address are to: 1) Determine the physical mechanisms responsible for the development of strong mid-level vortices and the conditions that favor their occurrence, 2) Identify the processes leading to the formation of a small surface concentrated vortex, and 3) Determine the effect of vertical wind shear, including a mean flow, on the pathway taken to tropical cyclogenesis.