Roles of ENSO in the Link of the East Asian Summer Monsoon to the Ensuing Winter Monsoon

The link between the East Asian summer monsoon (EASM) and the ensuing East Asian winter monsoon (EAWM) is investigated. The results found that strong (weak) EASM years are often followed by the strong (weak) EAWM years, demonstrating that the in-phase EASM to EAWM transition dominate the EASM-EAWM link. The strong EASM to the strong EAWM transition is established by an anomalous anticyclone over the western North Pacific (WNPAC) in summer and an anomalous cyclone (WNPC) in winter. The weak EASM to the weak EAWM transition is connected by the same way but with the WNPC in summer and the WNPAC in winter. Further studies suggest that ENSO plays a crucial role in the in-phase EASM to EAWM transition, which forces the transition between the WNPC and WNPAC from summer to winter via inducing Rossby wave responses to the ENSO-induced convection anomalies. Numerical simulation analysis further confirms the dominant role of ENSO in the in-phase EASM to EAWM transitions. The asymmetric analysis suggests that the in-phase EASM to EAWM transition is stronger under El Nino than under La Nina.

Automated summary

The study explores the connection between the East Asian summer monsoon (EASM) and the following East Asian winter monsoon (EAWM), finding that strong (weak) EASM years are typically followed by strong (weak) EAWM years. The transition from strong EASM to strong EAWM is influenced by anomalous anticyclones and cyclones over the western North Pacific region, while weak EASM to weak EAWM transitions occur in a similar manner but with reversed weather patterns. ENSO is identified as playing a crucial role in these transitions, with El Nino events showing a stronger impact on the EASM to EAWM transition compared to La Nina events.