Abstract/Summary

This study demonstrates that the concurrent influence of ENSO caused by the poleward translation of extra-tropical cyclones (ECs) over the North Atlantic is more significant than the 1-year lagged impact of ENSO through poleward propagating atmospheric angular momentum. Specific results show that during El Niño (La Niña) winter, the anomalous atmospheric horizontal heat advection from the Pacific to the Atlantic, which is caused by the southward (northward) displacement of the westerly jet stream, enhances (weakens) the atmospheric baroclinicity over the subtropical North Atlantic. Subsequently, the modified baroclinicity drives intensified (reduced) baroclinic energy conversion from the eddy available potential energy to the eddy kinetic energy, which shifts the genesis locations of ECs southward (northward) and suppresses (enhances) their poleward translation into the Arctic. Ultimately, through the combined thermodynamic and dynamical forcing inherent to ECs activity, the negative (positive) AO pattern is generated in the concurrent El Niño (La Niña) winter.