Dynamics of Spatio-Temporal Complexity: Baroclinic Flows at Moderate to Large Supercriticality

9523479 Mundt和Vallis斜压流动的数值模拟和实验室模拟表明，中超临界斜压系统可以表现出广泛的行为(例如，稳定的、周期的、混沌的)。此外，即使当流动只是边缘不稳定时，也可以存在非周期的、时间上不规则的解，即，在较小的超临界值处也是如此。以前的大多数动力学研究都是针对这一参数范围进行研究，该参数范围对应于比地球物理上现实的驱动更低的驱动。在更现实的参数范围内的研究通常是用更复杂的模型进行的，并提供了更多的经验结果，往往依赖于统计描述，而不是对动态的更彻底的理解。因此，在大气流动的超临界范围内，人们对从混沌到湍流的转变知之甚少。主要研究人员将根据他们的假设，即平均流超临界程度的水平与涡流的无序程度直接相关，对超临界流日益增加的流动的复杂性(无序)进行研究。他们将探索在低超临界下观察到的行为在多大程度上也可以在地球物理上更接近超临界的范围内观察到。将使用不同复杂性的模型，尽管最初的工作将集中在两层准地转模式上。将使用从经验正交函数分析到小波分析的各种分析工具。这项研究的重要性在于有可能更好地了解大气的可变性，并对广泛的天气和气候问题具有重要影响，包括气候模式中天气制度的转变和经向热通量的参数化。***

9523479 Mundt and Vallis Numerical and laboratory simulations of baroclinic flows have revealed that moderately supercritical baroclinic systems can exhibit a wide range of behavior (e.g., steady, periodic, chaotic). Moreover, aperiodic, temporally-irregular solutions can exist even when the flow is only marginally unstable, that is, at small values of supercriticality. Most previous dynamics studies have been directed to studying this parameter range which corresponds to lower driving than is geophysically realistic. Studies in more realistic parameter ranges are usually conducted with more complex models and have provided more empirical results, often relying on statistical descriptions, rather than a more thorough understanding of the dynamics. Thus, little is known about the transition from chaos to turbulence in the supercriticality range characteristic of atmospheric flows. The principal investigators will carry out a study focused on the complexity (disorder) of flows with increasing supercriticality, guided by their hypothesis that the level of mean flow supercriticality is directly related to the disorder of the eddy flow. They will explore the extent to which behavior observed at low supercriticality is also observed at more geophysically realistic ranges of supercriticality. Models of varying complexity will be employed, although the initial effort will focus on a two layer, quasi-geostrophic model. A variety of analysis tools, from empirical orthogonal function analysis to wavelet analysis, will be employed. The importance of this study lies in the potential for better understanding of the variability of the atmosphere, and has important implications a wide range of weather and climate issues, including weather regime transitions and parameterization of meridional heat flux in climate models. ***