[A-CG30] 熱帯におけるマルチスケール大気海洋相互作用

[ACG30-11] インド洋ダイポールモード現象に伴う海面水温偏差と大気テレコネクションの非対称性

中里 舞¹、木戸 晶一郎²、*東塚 知己^1,2 (1.東京大学大学院理学系研究科地球惑星科学専攻、2.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)

キーワード：インド洋ダイポールモード現象、混合層熱収支解析、大気テレコネクション、インド洋熱帯域

One of the important features of the Indian Ocean Dipole (IOD) is its asymmetry; negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD. Based on an online mixed layer heat budget analysis using the Regional Ocean Modeling System, it is shown that the vertical diffusion term plays an important role in generating this asymmetry in addition to the contributions from the nonlinear advection and the thermocline feedback proposed by some previous studies. To understand the origin of the asymmetry in the vertical diffusion term, a detailed decomposition is carried out. It is found that the asymmetry is primarily explained by differences in subsurface temperature anomalies; during positive IOD events, anomalous cooling below the mixed layer contributes to SST cooling via vertical mixing. However, such effects are weaker in the case of negative IOD events due to weaker subsurface temperature anomalies. Furthermore, analyses of the Rossby wave source and wave activity fluxes suggest that the SST asymmetry in the IOD indeed have asymmetric impacts on the mid-latitudes via atmospheric teleconnection.