Energetics of Atmospheric Meridional Teleconnection Patterns over the North Pacific in Winter

Abstract The western Pacific (WP) pattern, the North Pacific Oscillation (NPO), and the Pacific–North American (PNA) pattern are known as dominant meridional teleconnection patterns over the wintertime North Pacific. To investigate why these specific patterns are dominant, the energetics of atmospheric meridional teleconnection patterns over the wintertime North Pacific are comprehensively examined. A total of 286 meridionally dipolar circulation anomaly patterns are systematically extracted as regression anomalies onto 500-hPa zonal wind anomalies at various locations over the basin. Taking energy conversion/generation efficiency as a key metric, this study evaluates energy conversion with the climatological-mean state, feedback forcing from modulated high-frequency eddies, diabatic energy generation, and energy flux from the tropical atmosphere for each of the patterns. For all the patterns obtained from intraseasonal variability, baroclinic available potential energy conversion from the climatological-mean state contributes most efficiently to their maintenance. Meanwhile, barotropic kinetic energy conversion from the climatological-mean flow tends to play a secondary role, but it becomes more important if situated in the jet exit. As a net, energy conversion from the climatological-mean state and energy transfers from modulated high-frequency eddies act to energize all the patterns. Significant differences are found in net energy conversion efficiency among the patterns, arising mostly from differences in the efficiency of conversion from the climatological-mean state. Furthermore, the three dominant teleconnection patterns bear higher net conversion efficiency. In fact, net conversion efficiency is strongly correlated with the total energy possessed by each pattern, indicating a crucial role of the net energy conversion efficiency in the dominance of teleconnection patterns.