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生成，是一个复杂的过程，涉及大规模环境和较小规模大气扰动之间的相互作用。 有多种理论试图描述扰动在成为热带风暴的道路上所采取的路径。 在这个项目中，研究人员将使用先进的高分辨率数值模拟来分析其中两个途径所涉及的过程。 更好地了解热带气旋如何形成将有助于预报员和改善公共安全，特别是在小风暴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。热带气旋生成的第一条路径的特征是气旋性表面风的旋转和深对流塔中心的涡度建设。 第二种是中层低涡，在大尺度环流中心附近有一个小的地面集中低涡。 研究计划是使用区域大气模拟系统（RAMS）进行理想化的数值试验，新的riming和地面通量方案和天气研究和预报（WRF）模式与移动嵌套网格。 该项目将解决的主要目标是：1）确定负责发展强中层涡旋的物理机制和有利于其发生的条件，2）确定导致形成小的表面集中涡旋的过程，和3）确定垂直风切变的影响，包括平均气流，对热带气旋生成的路径。

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.