[A-AS05] 成層圏・対流圏過程とその気候への影響

[AAS05-P06] Hindcasts of the 2016 Disruption of the Stratospheric Quasi-biennial Oscillation

*渡辺 真吾¹、Kevin Hamilton²、Scott Osprey³、河谷 芳雄¹、西本 絵梨子 (1.国立研究開発法人海洋研究開発機構、2.International Pacific Research Center, University of Hawaii at Manoa、3.NCAS-Climate, University of Oxford)

キーワード：quasi-biennial oscillation、Rossby wave、extended range hindcast

In early 2016 the quasi-biennial oscillation in tropical stratospheric winds was disrupted by an anomalous easterly jet centered at ~40 hPa, a development that was completely missed by all operational extended range weather forecast systems. This event and its predictability are investigated through ensemble hindcasts using a global model notable for its sophisticated representation of the upper atmosphere. Key to prediction of this event is simulating the slowly evolving mean winds in the winter subtropics that provide a waveguide for Rossby waves propagating from the winter hemisphere. Its association to the strong El Nino condition in 2015 is also investigated by changing sea surface temperatures.