[A-CG30] 熱帯におけるマルチスケール大気海洋相互作用

[ACG30-P03] External and Internal forcings of the Indian Ocean Dipole

*Lianyi Zhang^1,2、Yan Du^1,2、Tomoki Tozuka³ (1.South China Sea Institute of Oceanology, Chinese Academy of Sciences、2.Southern Marine Science and Engineering Guangdong Laboratory、3.Dept. of Earth and Planetary Science Graduate School of Science, Univ. of Tokyo)

キーワード：Indian Ocean Dipole , ENSO , Tropical-Extratropical Interaction

The Indian Ocean Dipole (IOD) is a climatic phenomenon occurring in the tropical Indian Ocean, which can cause anomalous weather and climate over the surrounding rims even the globe. This study investigates the remote impacts of the El Nino-Southern Oscillation (ENSO), and the internal forcing from the southern Indian Ocean on the IOD. The ENSO impacts on the IOD are revisited by a new statistical method namely the Combine Linear Regression (CLR). When the ENSO impacts are isolated, the IOD survives with same phase-locking to boreal fall season, while it weakens and peaks earlier by 1 month. After removing the ENSO impacts by the CLR, we propose a new triggering mechanism of IOD originating from the Southern Hemisphere, namely the Southern Hemisphere Mechanism (SHM). The SHM is independent from ENSO and cooperate with ENSO to affect the IOD in fall, leading to the IOD diversity such as the unseasonable IOD. The subtropical high in the southern Indian Ocean and high-latitude climate activities play important roles in the SHM. To consider these forcings would help to improve the IOD predictability.