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

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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.