[A-CG30] 中緯度大気海洋相互作用

[ACG30-08] The Northern Annular Mode phase distorted by the Boundary Current Synchronization

*神山 翼¹、山上 遥航²、木戸 晶一郎²、小川 史明³、三浦 裕亮⁴、建部 洋晶² (1.お茶の水女子大学理学部情報科学科、2.海洋研究開発機構、3.北海道大学、4.東京大学)

キーワード：境界流同期、北半球環状モード、異常気象、大気海洋相互作用

Synchronized variability between two Northern Hemispheric western boundary currents, the Boundary Current Synchronization (BCS), is associated well with meridional migrations of the atmospheric jet stream. Based on observational evidence, BCS exhibits covariability with the Northern Annular Mode (NAM), the most prominent internal mode of atmospheric variability that controls the latitudinal position of the jet stream in Northern Hemispheric winter. Therefore, in this study, we have performed a set of high-resolution pacemaker experiments where sea surface temperatures in the two boundary current regions are strongly relaxed to a preindustrial control run. These eddy-permitting pacemaker runs show that BCS actively supports the existence of extreme NAM events, which directly affects the abnormal weather events in winter. The extent to which boundary currents affect the NAM phase varies among different ensemble members, so the BCS influence on NAM is sensitive to stochasticity.