Program     Ocean-atmosphere interactions and multi-scale climate variability in a changing climate       Poster A possible mechanism for the impacts of the Madden-Julian Oscillation on the North Atlantic Oscillation P-P2-09 Xiaolu Shao* , Hohai University Jie Song, Institute of Atmospheric Physics Shuanglin Li, Institute of Atmospheric Physics Presenter Email: shaoxl06@163.com After the onset of the MJO phase 3 (6), a wave train over the Pacific-North American (PNA) region with an anticyclone anomaly over the northeastern Pacific are formed and developed, then followed by a positive (negative) NAO-like pattern over the North Atlantic sector. The atmospheric responses to the initial-value perturbations aroused by tropical heating forcing of the MJO are simulated using the Geophysical Fluid Dynamics Laboratory (GFDL) dynamical core model. Compared with the control experiment, the initial-value perturbations over the Indian Ocean aroused by the tropical heating of the MJO phase 3 (6) can lead to faster (slower) eastward speed of synoptic eddies over the North Atlantic, driving the formation of the synoptic eddy vorticity forcing (EVF) associated with the positive (negative) NAO. In response to the initial-value perturbations over the Indian Ocean, the circumglobal teleconnection pattern is formed, while the Atlantic jet strengthens (weakens). The observational results show that after the strengthening (weakening) of the subtropical Asian jet associated with the MJO phase 3 (6), the synoptic eddies over the North Atlantic have faster (slower) eastward speed. Therefore, we provide a possible mechanism for the impacts of the MJO on the NAO. Firstly, circulation anomalies over the Indian Ocean are aroused by the anomalous heating of the MJO phase 3 (6). Then, through the circumglobal teleconnection pattern, the Atlantic jet strengthens (weakens). Finally, the synoptic eddies have faster (slower) eastward speed, producing the anomalous EVF and thus driving the formation of the positive (negative) NAO.

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