Persistent Flow Anomalies, Blocking and Variations in Synoptic-Scale Eddy Activity. Theoretical and Diagnostic Studies

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The primary goal of this research is to obtain an improved understanding of the mechanisms that determine the evolution of large-scale flow anomalies such as blocking. A second major goal is to determine how the large-scale flow anomalies may influence (and be influenced by) synoptic-scale eddies. In order to achieve these goals, a combination of approaches will be employed to study the variations in synoptic-scale eddy activity and the roles of various dynamical and physical processes during different stages in the evolution of the large-scale flow anomalies. Specific objectives of the proposed studies include: applying synoptic and diagnostic approaches to analyze and compare numerical simulations of low-frequency variability in the NCAR Community Climate Model with corresponding observational results, with particular emphasis given to assessing the adequacy of model simulation of the structures and life cycles of persistent anomalies and blocking. Diagnostic analyses will also be employed to examine the relationships (in both the model and observations) between the large-scale flow anomalies and changes in synoptic-scale eddy activity at various stages in the evolution of the large-scale flow patterns (i.e., during the development, mature and breakdown stages). In addition, extensions to current analytical and theoretical models of blocking will be developed, concentrating particularly on the coherent structure models of Malguzzi and Malanotte-Rizzoli (1984) and Haines and Marshall (1987). These models will be employed to further examine the roles played by various dynamical and physical processes in the initiation, persistence and breakdown of the anomalous large-scale flow patterns. This work will enhance our capability to make seasonal forecasts.