Dryline Dynamics

9729631干线是两个不同气团之间的表面边界，这两个气团经常在春季和初夏居住在美国中南部。这条线的东面是一个相对较浅的凉爽潮湿的海洋气团，西面是一个较深的温暖干燥的大陆气团。这一中尺度现象意义重大，因为它往往与恶劣天气(破坏性大风、冰雹和龙卷风)的发生有关。雷雨倾向于沿着干线和干线以东发展。干线通常在白天向东迁移数百公里，然后在晚上向西逆行。这种干线的昼夜变化使恶劣天气的预报成为一项重大挑战。这项研究的目的是模拟干线的结构和位置的日变化。基本的方法是将干线视为浅层海洋气团的西缘。这个气团的动力学将首先使用一种被称为浅水模型的简化数值模型来研究。将确定模型干线对质量、动量和热力的敏感性，并与现有理论进行比较。然后将开发一个气团的平板混合层模式，以更准确地表示主要的热力学过程。模型工作的改进包括二维研究和对多个气团的扩展。这种使用介于分析理论和复杂的中尺度数值模式之间的中等复杂性模型的理论方法，应该能够捕捉到基本的物理学，并提供对干线动力学的洞察。研究结果将有助于更好地了解干燥线，并有助于恶劣天气的预报。***

9729631 Bannon The dryline is the surface boundary between two distinct air masses that frequently inhabit the south central United States in Spring and early Summer. To the east of the line lies a relatively shallow cool moist maritime air mass and to the west a deeper warm dry continental air mass. This mesoscale phenomenon is significant because it is often linked to the occurrence of severe weather (damaging winds, hail and tornadoes). Thunderstorms tend to develop along and to the east of the dryline. The dryline often migrates several hundred kilometers to the east during the day and then retrogrades westward during the night. This diurnal evolution of the dryline helps make the forecasting of severe weather a major challenge. The purpose of this research is to model the diurnal evolution in structure and position of the dryline. The fundamental approach is to treat the dryline as the western edge of a shallow layer maritime air mass. The dynamics of this air mass will first be studied using a simplified numerical model know as the shallow water model. The sensitivity of the model dryline to mass, momentum, and thermal forcings will be ascertained and compared with existing theories. A slab mixed- layer model of the air mass will then be developed to more accurately represent the major thermodynamic processes. Refinements of the modeling effort include two dimensional studies and an extension to multiple air masses. This theoretical approach of using models of intermediate complexity between analytic theory and sophisticated mesoscale numerical models should be able to capture the essential physics and provide insight into the dynamics of the dryline. The results of the research should provide a better understanding of the dryline and help the forecasting of severe weather. ***