Classification Of Wintertime Atmospheric Teleconnection Patterns In The Northern Hemisphere

Energetics of the major atmospheric teleconnection patterns of the Northern Hemisphere winter are examined to investigate the role of baroclinic and barotropic energy conversions in their growth. Based on characteristics of the energetics and the horizontal structures, the patterns are classified into three general types: meridional dipole (D-type), wave (W-type), and hybrid (H-type). The primary energy conversion term that differentiates these patterns is the baroclinic energy conversion of the available potential energy from the climatology to the eddy field associated with the teleconnections. For this conversion term, D-type patterns exhibit the comparable conversion of potential energy via the eddy heat flux across the climatological thermal gradient in both the zonal and meridional directions. In contrast, baroclinic conversion for W-type patterns occurs primarily in the meridional direction, while H-type patterns exhibit a structure that combines the characteristics of the other two pattern types. An important secondary factor is barotropic conversion from the climatology to the eddy field, which takes place mainly in the regions where the climatological shear is strong. For the D-type patterns, conversion occurs on the flank of the climatological jet exit, while it occurs at the center of the jet exit for the W-type patterns. Last, for all the patterns, synoptic-time-scale eddies make a negative contribution via the baroclinic process, but a positive contribution via the barotropic process. Damping by diabatic heating weakens the temperature anomalies associated with the patterns.