16:40 〜 16:55
[ACG32-08] マダガスカル島沿岸での南赤道海流の分岐および西岸境界流の経年変動とENSOとの関係
キーワード：インド洋, 南赤道海流, 西岸境界流, Island Rule, ENSO
The South Equatorial Current (SEC) in the Indian Ocean bifurcates at the east coast of Madagascar into Northeast and Southeast Madagascar Currents (NEMC and SEMC). In this study, the dynamical mechanism of the SEC bifurcation latitude (SBL), NEMC, and SEMC variations associated with the basin-scale wind variation are investigated using observational data, reanalysis data and the outputs from an atmospheric general circulation model (AGCM). It is found that the interannual NEMC and SEMC variations are dominated by the SEC variations rather than the SBL. Based on the Time-dependent Island Rule calculations, it is also found that the interannual anomalies of the SBL and the NEMC and SEMC transports are the responses to the meridional interior transport, which in turn is a result of westward popagating Rossby waves from 70oE-90oE.
The SBL, NEMC, and SEMC have correlation with Niňo 3.4 index with 5-15 month lags, and the wind stress curl fields around 80oE-110oE, 20oS-10oS have positive correlation with the Niňo 3.4 index from the late 1990s to the 2000s. From an analysis of AGCM sensitivity experiment, the wind stress curl anomalies around 60oE-90oE, 25oS-15oS may be because of the Matsuno-Gill response to diabatic heating anomalies in the western Pacific, whereas those around 80oE-110oE, 20oS-10oS may be due to the sea surface temperature anomalies off the west coast of the Australia that tend to appear during ENSO events.
The SBL, NEMC, and SEMC have correlation with Niňo 3.4 index with 5-15 month lags, and the wind stress curl fields around 80oE-110oE, 20oS-10oS have positive correlation with the Niňo 3.4 index from the late 1990s to the 2000s. From an analysis of AGCM sensitivity experiment, the wind stress curl anomalies around 60oE-90oE, 25oS-15oS may be because of the Matsuno-Gill response to diabatic heating anomalies in the western Pacific, whereas those around 80oE-110oE, 20oS-10oS may be due to the sea surface temperature anomalies off the west coast of the Australia that tend to appear during ENSO events.