日本地球惑星科学連合2023年大会

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[E] 口頭発表

セッション記号 A (大気水圏科学) » A-CG 大気海洋・環境科学複合領域・一般

[A-CG30] 中緯度大気海洋相互作用

2023年5月21日(日) 13:45 〜 15:00 201A (幕張メッセ国際会議場)

コンビーナ:関澤 偲温(東京大学先端科学技術研究センター)、桂 将太(東京大学大気海洋研究所)、安藤 雄太(九州大学)、木戸 晶一郎(海洋開発研究機構 付加価値創生部門 アプリケーションラボ)、座長:木戸 晶一郎(海洋開発研究機構 付加価値創生部門 アプリケーションラボ)、安藤 雄太(鈴鹿工業高等専門学校)


14:30 〜 14:45

[ACG30-09] Modulations of Northern Annular Mode due to global warming

*臼井 健人1川村 岳1岡島 悟2関澤 偲温2宮本 歩2、戸田 賢希2小坂 優2中村 尚2 (1.東京大学理学部地球惑星物理学科、2.東京大学先端科学技術研究センター)


キーワード:北半球環状モード、温暖化、エルニーニョ・南方振動

Modulations of the winter Northern Annular Mode (NAM) under global warming are investigated using ERA5 reanalysis data and the outputs from historical and +4K global warming simulations of d4PDF. Thanks to the large ensemble size of d4PDF, the modulations of the NAM can be detected with great significance, and it is possible to separate atmospheric variability into internal variability and variability due to external forcing (mainly SST variability). It is found that the structure and amplitude of sea-level pressure anomalies associated with NAM in d4PDF historical simulations are mostly consistent with those of ERA5, albeit with excessively strong anomalies at the Pacific center of action (near the Aleutian low). Comparison between historical simulation and +4K simulations shows that the sea-level pressure anomalies around the Pacific center of the action strengthens with global warming. Besides the fraction of variance due to external (SST) forcing greatly rises from 9.4% to 32.1%. These suggest that global warming enhances the influence from ENSO on NAM. There are two possible explanations for this change. First, the pattern of equatorial Pacific precipitation anomalies associated with ENSO shifts eastward with global warming, which displaces the teleconnection pattern eastward with stronger influence on the North Atlantic sector of NAM. Second, the background westerlies get stronger and the wavelength of the stationary Rossby waves increases. We also examined the transient eddy activity changes associated with ENSO, and found that the anomalies extend more downstream toward the North Atlantic in the warmer climate. This suggests that the transient eddy activity anomalies associated with ENSO have stronger feedback to North Atlantic circulation anomalies associated with NAM in the warmer climate.