日本地球惑星科学連合2018年大会

講演情報

[EE] Eveningポスター発表

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

[A-CG34] 中緯度海洋と大気

2018年5月21日(月) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:西川 はつみ(北海道大学 低温科学研究所)、佐々木 克徳(Hokkaido University)、岡島 悟(東京大学先端科学技術研究センター、共同)、Thomas Spengler(University of Bergen)

[ACG34-P06] Mechanisms for Maintaining Basin-Scale Atmospheric Response to Decadal Variability of the North Pacific Oceanic Frontal Zone

*岡島 悟1中村 尚1西井 和晃2宮坂 貴文1吉田 聡3田口 文明1森 正人1小坂 優1 (1.東京大学先端科学技術研究センター、2.三重大学、3.京都大学)

キーワード:大気海洋相互作用、海洋前線

Through the following two ensemble experiments with an atmospheric general circulation model (AGCM), mechanisms for the maintenance of a large-scale wintertime atmospheric response to warm sea surface temperature (SST) anomalies associated with decadal-scale poleward displacement of the North Pacific subarctic frontal zone (SAFZ) has been investigated. The ensemble experiments are as follows: one with climatological-mean SST and the other with positive SST anomalies along the SAFZ prescribed on top of the climatological-mean SST.
As actually observed, the simulated January ensemble response over the North Pacific is anticyclonic throughout the depth of the troposphere, although its amplitude is smaller. This response is maintained through energy conversion from the ensemble climatological-mean circulation realized under the climatological SST as well as feedback from anomalous transient eddy activity, suggesting that the response may have a characteristic as a preferred mode of variability (or “dynamical mode”). Conversions of both available potential energy and kinetic energy from the climatological-mean state are important for the observed anomaly, while the latter is less pronounced for the model response. Net transient feedback forcing is also important for both the observed anomaly and simulated response. These results imply that moderate horizontal resolution (~1 degree) AGCM may be able to simulate a basin-scale atmospheric response to the SAFZ SST anomaly through synoptic and basin-scale dynamical processes. Weaker PNA-like internal variability in the model may lead to the weaker response, suggesting that misrepresentation of intrinsic atmospheric variability can affect the model response to the SST anomaly.