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Ocean-atmosphere interactions and multi-scale climate variability in a changing climate
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The Indian Ocean equatorial surface divergence and subsurface convergence and their relation to the dynamic of equatorial zonal currents during positive IOD
Tuesday 8th @ 1530-1550, Concert Hall
Weiqiang Wang* , South China Sea Institute of Oceanology, CAS
Huibin Xing, South China Sea Institute of Oceanology, CAS
Presenter Email: weiqiang.wang@scsio.ac.cn |
| The features of the Indian Ocean equatorial meridional currents and their linkage with zonal currents associated with the Indian Ocean Dipole (IOD) are examined using the European Centre for Medium-Range Weather Forecasts (ECMWF) Ocean Reanalysis System 4 (ORAS4). At the peak of IOD (Oct-Nov), significant anomalous equatorial surface (0-50m) divergence and subsurface (50-150m) convergence are found in the tropical Indian Ocean. The surface divergence region lies in from the central to western Indian Ocean basin (55E-80E), however, the subsurface convergence locates in the eastern basin (70E-90E). The dismatch of surface divergence and subsurface convergence zones is investigated. The subsurface convergence is caused by equatorward mass transport with results from anomalous wind curls in the off-equatorial regions of both the northern and southern Indian Ocean. The surface divergence is caused by both equatorial east wind anomaly and upwelling due to subsurface convergence and appears west off 80E due to pile-up effect of westward current anomaly induced by east wind anomaly. Furthermore, the surface divergence is found to be close related to the Wyrtki Jet (WJ), which is a strong eastward surface flow and appears at 60E-90E during IOD peak seasons. And, the subsurface convergence is close related to the Equatorial Undercurrent in the (EUC), which is a strong eastward subsurface flow and normally appears in the western ocean basin but extends to the eastern basin during positive IOD events. The results suggest the linkage of meridional and zonal currents in the equatorial Indian Ocean, which is essential for upper ocean circulation systems in the tropical Indian Ocean. |
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