Further Study of Dynamics of Low-Frequency Variability of the Extratropical Atmospheric Circulation

几十年来的研究已经认识到，大气低频流动异常与天气涡活动之间的内部动力反馈在维持热带外大气低频变率中起着至关重要的作用。然而，其潜在的机制尚不完全清楚。该项目建立在先前项目的基础上，即明确描述天气涡旋和低频流（SELF）相互作用动力学的动态闭合，该项目寻求继续这种方法，以研究超越月-季节时间尺度的大气环流异常形成机制及其激发机制。具体而言，研究人员提出了与正自我反馈相关的天气涡诱导的动态不稳定性作为低频行星尺度变率的基本机制之一。通过理论分析、动力学建模和利用模型输出和再分析数据集进行诊断等一系列研究，本项目将进一步研究：(1)天气涡引起的动力不稳定的性质，(2)这种不稳定在温带气候模式和行星尺度气候流异常的产生中的作用，以及(2)它对中纬度海气动力耦合的影响。这项研究将有助于提高我们对温带气候变率及其可预测性的认识。它将对气候科学的几个领域产生影响，包括中纬度风暴路径的变率，北极振荡/北大西洋振荡，以及中纬度海洋-大气动力耦合。

Internal dynamic feedback between atmospheric low-frequency flow anomalies and synoptic-eddy activity has been recognized through decades of research as playing an essential role in maintaining the extratropical atmospheric low-frequency variability. However, the underlying mechanism is not fully understood. Building on the prior project on the development of a dynamical closure that explicitly describes the dynamics of the synoptic eddy and low-frequency flow (SELF) interaction, this project seeks to continue this approach to investigate the mechanisms for the formation of atmospheric circulation anomalies beyond month-to-seasonal timescales and their excitation mechanisms. Specifically, the investigators propose a synoptic-eddy induced dynamic instability related to the positive SELF-feedback as one of the basic mechanisms for low-frequency planetary-scale variability. Through a hierarchy of studies including theoretical analysis, dynamical modeling, and diagnostics using both model outputs and reanalysis data sets, this project will further study (i) the nature of the synoptic-eddy induced dynamic instability, (ii) the roles of this instability in the generation of the extratropical climatic modes and planetary-scale climatic flow anomalies, and (ii) its impact on middle latitude air-sea dynamical coupling.This study will aid in the advancement of our understanding of extratropical climate variability and its predictability. It will have impacts on several areas of climate science, including variability of the mid-latitude storm tracks, and Arctic oscillation/North Atlantic oscillation, and middle latitude ocean-atmosphere dynamical coupling.