Predictability and Maintenance of Variance in Atmospheric Flows

该奖项继续支持旨在发展大气流动的一般稳定性理论以及中纬度急流等强剪切流中的湍流动力学理论的研究。首席研究员将利用理论模型和综合环流模型（GCM）模拟分析来实现这些目标。该项目涉及两个主要的重点。第一个奖项建立在上一个奖项下完成的理论工作的基础上。目的是确定具有实际纬向变化射流结构的GCM随机强迫维持的方差和通量，并将这些方差和通量与从GCM长时间积分统计方法获得的方差和通量进行比较。将使用NCAR的社区气候模型（CCM2）的一个版本。人们希望这项研究将阐明在特定地区产生风暴局部化的动力学以及风暴路径对变化的敏感性。该项目将与NCAR的一位科学家合作完成。第二个研究重点是对湍流模型系统和gcm及其稳定性的基础算子进行更理论化和广义化的研究。如果时间允许，将进行另一个专题。本研究将检验时间依赖流的稳定性——具体来说，扰动的瞬态增长与时间平均流和第一Lyapunov模态的出现之间的关系，以及非正态性在支持短时间误差增长和渐近Lyapunov模态中的作用。＊＊＊

9623539 Farrell The award continues support for research aimed at developing a general stability theory for atmospheric flows as well as a theory for the dynamics of turbulence in strongly sheared flows such as the midlatitude jet. The principal investigator will pursue these goals using a combination of theoretical models and analysis of simulations with a general circulation model (GCM). The project involves two major thrusts. The first builds on theoretical work completed under the last award. The aim is to determine the variance and fluxes maintained by stochastic forcing of a GCM with realistic zonally varying jet structure and to compare these variances and fluxes with those obtained from the statistical means of a long time integration of the GCM. A version of NCAR's Community Climate Model (CCM2) will be used. It is hoped that this study will shed light on the dynamics responsible for producing localization of storms in particular regions and the sensitivity of storm tracks to alteration. The project will be done in collaboration with an NCAR scientist. The second research focus involves a more theoretically focused and generalized study of the underlying operator in turbulent model systems and GCMs and its stability properties. An additional topic will be undertaken if time permits. This study will examine the stability of time dependent flows - specifically, the relationship between transient growth of perturbations to the time mean flow and the emergence of the first Lyapunov mode and the role of non-normality in supporting both the short time error growth and the asymptotic Lyapunov modes. ***