Effects of Wave-Mean Flow Interaction on the Multi-Time-Scale Variability of the AO Indices: A Case Study of Winters 2007/08 and 2009/10

Wave-mean flow interaction is usually regarded as accounting for the origin of Arctic Oscillation/Northern Hemisphere Annular Mode (AO/NAM). It inferred that combination local wave-mean interactions at AO/NAM’s three regional centers action on important time scales contributes to main behavior AO/NAM index. To discuss variations indices prominent scales, we take 2007/08 and 2009/10 winters two comparative examples analyze centers. The following facets are identified: (1) Synoptic-scale wave breakings in North Atlantic can explain variances index a scale 10–20 days. In winter, there were both cyclonic anticyclonic synoptic breakings, while breaking was dominant, characteristics strikingly similar blocking. (2) winters, signals 30–60 days mainly from between upward propagating quasi-stationary waves polar vortex stratosphere. (3) This work also demonstrates linked El Niño–Southern Oscillation (ENSO) by Pacific–North American pattern (PNA) winter mean scale. (2009/10) La Niña (El Niño) forced Pacific jet shift poleward (equatorward), favor weakening (enhancing) waveguide; thus, became stronger (weaker), corresponding positive (negative)