An identification of the mechanisms that lead to arctic warming during planetary-scale and synoptic-scale wave life cycles

The dynamical mechanisms that lead to wintertime Arctic warming during the planetary-scale wave (PSW) and synoptic-scale wave (SSW) life cycles are identified by performing a composite analysis of ERA-Interim data. The PSW life cycle is preceded by localized tropical convection over the western Pacific. Upon reaching the midlatitudes, the PSWs amplify as they undergo baroclinic conversion and constructively interfere with the climatological stationary waves. The PSWs flux large quantities of sensible and latent heat into the Arctic, which produces a regionally enhanced greenhouse effect that increases downward IR and warms the Arctic 2-m temperature. The SSW life cycle is also capable of increasing downward IR and warming the Arctic 2-m temperature, but the greatest warming is accomplished in the subset of SSW events with the most amplified PSWs. Consequently, during both the PSW and SSW life cycles, wintertime Arctic warming arises from the amplification of the PSWs.