Discretely Propagating Fronts

9528853 Fritsch虽然锋面的基本物理已经知道很多年了，但新的观测工具和理论框架正在推动对一些经典概念的重新评估。多年来观察到，锋面边界有时似乎以离散而不是连续的方式传播。虽然经常观察到这种行为，但还没有很好的记录，也没有任何深入的研究。首席研究员建议开始一项关于离散传播前沿的探索性研究。其目的是：1)建立离散传播锋面及其环境的特征，2)确定锋面以阶梯状(离散)方式传播的原因和方式，3)将离散传播过程与现有的锋生理论联系起来，4)构建离散传播的概念模型。研究方法由四部分组成：1)使用标准地面和高空资料汇编离散传播事件十年气候学，2)汇编个别事件的性质和复合环境的构建，3)对一个典型事件进行数值模拟(S)，4)计算对整个模式区域的锋生和整个事件生命周期有贡献的每个项(过程)的演变(S)。在这项初步研究工作中，主要重点将放在目标1和目标2上。虽然预计在其余目标方面会取得一些进展，但只有在完成这项探索性工作后才会提出的后续研究工作才会对它们进行更全面的攻击。预计从这些调查中获得的知识将加强我们对锋生如何与潜在涡度异常有关的理解，以及最重要的是，为什么以及在什么条件下发生离散传播。预计结果将为L带来实际好处，例如改善短期(3-18小时)天气预报。这一结果也为锋生问题的进一步理论研究提供了依据。***

9528853 Fritsch While the fundamental physics of fronts has been know for many years, new observational tools and theoretical frameworks are driving a reevaluation of some of the classical concepts. It has been observed over the years that frontal boundaries sometimes appear to propagate in a discrete rather than continuous manner. While observed with some frequency, this behavior has not been well documented nor studied in any depth. The principal investigator proposes to begin an exploratory study of discretely-propagating fronts. The objectives are: 1) establish the characteristics of discretely-propagating fronts and their environment, 2) determine why and how fronts propagate in a step-like (discrete) manner, 3) relate the processes of discrete propagation to current theories concerning frontogenesis, and 4) construct a conceptual model of discrete propagation. The research methodology is composed of four parts: 1) compilation of a ten year climatology of discrete propagation events using standard surface and upper air data, 2) compilation of the properties of individual events and construction of a composite environment, 3) numerical simulation of a representative event(s), and 4) calculation of the evolution of each of the terms (processes) that contribute to frontogenesis over the entire model domain and for the complete life cycle of the event(s). Under this initial research effort primary emphasis will be on objectives 1 and 2. While some progress is expected on the remaining objectives, they will be attacked more fully under a subsequent research effort that will be proposed only if warranted after completion of this exploratory effort. It is expected that the knowledge gained from these investigations will enhance our understanding of how frontogenesis is related to potential vorticity anomalies and, most importantly, why, and under what conditions, discrete propagation occurs. It is anticipate that the results will provide practica l benefits, such as improvements in short-term (3-18 h) weather forecasts. The results should also provide a basis for further theoretical studies of the frontogenesis problem. ***