日本地球惑星科学連合2014年大会

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

[A-CG37_28PO1] 熱帯におけるマルチスケール大気海洋相互作用現象

2014年4月28日(月) 18:15 〜 19:30 3階ポスター会場 (3F)

コンビーナ:*名倉 元樹((独) 海洋研究開発機構)、長谷川 拓也(独立行政法人海洋研究開発機構)、清木 亜矢子(海洋研究開発機構)、東塚 知己(東京大学大学院理学系研究科地球惑星科学専攻)、時長 宏樹(ハワイ大学国際太平洋研究センター)、大庭 雅道(電力中央研究所 環境科学研究所 大気海洋環境領域)、今田 由紀子(東京大学大気海洋研究所)

18:15 〜 19:30

[ACG37-P05] 高解像度OGCMにおける赤道インド洋の東西運動量収支解析

*名倉 元樹1McPhaden Michael J2 (1.海洋研究開発機構、2.米国大気海洋庁)

キーワード:インド洋, 赤道ジェット, 運動量収支, 高解像度OGCM

This study examines the zonal momentum budget along the equator in the Indian Ocean, with emphasis on the Wyrtki Jets in a high-resolution ocean general circulation model. The Wyrtki Jets are wind-driven eastward flows in the upper 100 m of the equatorial Indian Ocean that appear typically twice per year during the monsoon transitions in boreal spring and fall. Our results indicate significant contributions from zonal, meridional and vertical advection of zonal momentum, with the dominant contribution coming from zonal momentum advection. These results contrast with those from previous idealized wind-forced model experiments that emphasized the importance of vertical momentum advection. The extra eastward force caused by zonal momentum advection reinforces eastward wind stress, resulting in swifter jets in the eastern basin than in the western basin. Another consequence of these nonlinearities is that, annually averaged, zonal currents in the upper thermocline flow against the zonal pressure gradient rather than down gradient. Thus, there is no mean subsurface undercurrent flowing against the surface winds in the Indian Ocean as there is in the Pacific and Atlantic Oceans. These results indicate that proper simulation of the mean and the semi-annual zonal flows along the equator in the Indian Ocean, including their climatically relevant impacts on the mass and heat balance of the region, requires accurate representation of nonlinearities that derive from a broad range of interacting time and space scales.