Discretely Propagating Fronts

小行星9528853 虽然前沿的基本物理学已经知道了很多年，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。 多年来已经观察到，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，但没有很好的记录，也没有进行任何深入的研究。 主要研究者建议开始对离散传播前沿进行探索性研究。 目标是：1）建立离散传播锋及其环境的特征; 2）确定锋为什么和如何以阶梯状（离散）方式传播; 3）将离散传播过程与当前锋生理论联系起来; 4）构建离散传播的概念模型。 研究方法由四部分组成：1）利用标准地面和高空数据编制离散传播事件的十年气候学，2）编制单个事件的特性和构建复合环境，3）代表性事件的数值模拟，（4）计算在整个模式域和事件的整个生命周期中对锋生有贡献的每个项（过程）的演变。 在这一初步研究工作中，主要重点将放在目标1和2上。 虽然预期在其余目标方面会取得一些进展，但将在随后的研究工作中更全面地探讨这些目标，只有在完成这一探索性努力后，如果有必要，才会提出这一研究工作。 预计从这些调查中获得的知识将提高我们对锋生如何与位涡异常相关的理解，最重要的是，为什么以及在什么条件下发生离散传播。预计这些结果将带来实际效益，例如改善短期（3-18小时）天气预报。这一结果也为进一步的锋生问题的理论研究提供了基础。 ***

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. ***