[A-AS10] 成層圏・対流圏 (大気圏) 過程とその気候への影響

[AAS10-08] 2021-22冬季の海面水温と海氷偏差への大規模大気循環応答

★招待講演

*西井 和晃¹、田口 文明²、中村 尚³、Orsolini Yvan⁴ (1.三重大学大学院生物資源学研究科、2.富山大学都市デザイン学部、3.東京大学先端科学技術研究センター、4.Climate and Environmental Research Institute (NILU))

キーワード：太平洋十年規模変動、ブロッキング、オホーツク海海氷、成層圏極渦強化

The 2021-22 winter was characterized by cooling of the Arctic stratosphere particularly around the late winter, extremely warm sea surface temperatures (SST) in the North Pacific associated with the negative phase of the Pacific Decadal Oscillation (PDO), and reduction of sea ice in the Sea of Okhotsk. We investigated the large-scale atmospheric responses to observed anomalies in the SST and sea ice in this winter through ensemble time-slice experiments of an atmospheric general circulation model (AGCM). An anticyclonic response to the observed anomalies in the extratropical SSTs and sea ice was found over the western North Pacific in the troposphere in February 2022, which is consistent with observed anticyclonic anomaly there. In the polar stratosphere, a cooling response was found in association with weakening of upward planetary wave propagation into the stratosphere. This is again consistent with the observation. Further experiments suggest that each of anomalies in the extratropical North Pacific SSTs, extratropical North Atlantic SSTs, and sea ice in the sea of Okhotsk may contribute to the tropospheric anticyclonic anomaly over the western North Pacific and cooling in the polar stratosphere. In contrast, significant responses consistent with the observation in the extratropical troposphere and stratosphere were not obtained in response to the observed tropical SST anomalies.