hide
Free keywords:
-
Abstract:
The western Pacific (WP) pattern, North Pacific Oscillation (NPO), and the Pacific-North American (PNA) pattern are dominant teleconnection patterns over the wintertime North Pacific, which are characterized by a meridional dipole of height anomalies. For comprehensive understanding of the relative importance of many possible processes for the maintenance of those patterns and key factors for their dominance over other possible patterns, we systematically extracted 286 meridional teleconnection patterns anchored to various locations over the wintertime North Pacific, from d4PDF large-ensemble simulations with an atmospheric general circulation model. We then evaluated efficiency of individual energy conversion processes with the climatological mean state or modulated high-frequency eddy activity and compared them among different teleconnection patterns.
For all the 286 atmospheric internally-driven meridional teleconnection patterns, baroclinic energy conversion (CP), which arises from the vertically phase-tilted height anomalies embedded in the baroclinic background state, has the largest contribution, while barotropic energy conversion (CK) plays a secondary role. The net adiabatic efficiency distribution has two maxima corresponding to the PNA pattern and the WP/NPO pattern. Indeed, total energy (kinetic and available potential energy) associated with a pattern tends to be larger when the pattern has higher net adiabatic efficiency, suggesting that energy conversion from the extratropical background state determines dominant meridional teleconnection patterns.
By contrast, externally-driven teleconnection patterns generally have lower net adiabatic efficiency compared to internally-driven patterns. Results suggest that not energy conversion efficiency, but other processes such as energy influx from the tropics determine dominance in the external teleconnection patterns.
