The Life Cycle Dynamics of Teleconnection Patterns

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The Pacific North Atlantic (PNA) and North Atlantic Oscillation (NAO) teleconnections are known to play a very important role in climate variability and perhaps climate change. Most studies have emphasized their time-averaged (i.e., monthly, interannual, and interdecadal) properties. However, the PIs recently found that both the PNA and NAO undergo full lifecycles of growth and decay within a time period on the order of two weeks, indicating that most PNA and NAO studies are examining data that is time-averaged over several life cycles. The framework for the relationship between climate variability/change and these teleconnections can be established only with a knowledge of the very nature of the physical processes involved in these teleconnections. The goal of this grant is to identify physical processes governing the evolution of both the PNA and NAO. The approach adopted combines both diagnostic analyses of observational data and also an examination of data from idealized model calculations. Specific questions that will be addressed are (i) the mechanisms that account for the excitation of the PNA and NAO; (ii) the dynamical processes that account for the saturation i.e. termination of growth of the PNA and NAO; (iii) the role of low-frequency fluxes in the growth and decay of the PNA and NAO; and (iv) how the short timescale properties of the PNA and NAO are related to interannual variability. The work is important because it will further basic understanding of the physical processes governing the life cycle of major teleconnection in the Northern Hemisphere. In addition, these results could impact the accuracy of forecasts on time scales of weeks to seasons.