Response of the South China Sea upper layer circulation to monsoon anomalies during 1997/1998 El Niño event

Abstract

One of the strongest El Niño events on record took place in the tropical Pacific in 1997–1998, causing remarkable changes in monsoon systems over the South China Sea (SCS) basin. This would induce prominent anomalies in the SCS upper layer circulation. The monsoon anomalies and the response of the upper layer circulation over the SCS during the 1997–1998 El Niño event are examined through data analysis and ocean numerical modeling, respectively. The winter monsoon and summer monsoon show southerly wind anomalies and northeasterly wind anomalies respectively during 1997/98 El Niño event, which was a reversal of the climatology. In contrast to climatology, the weakening of the winter monsoon does not change the upper layer circulation pattern, but causes a prominent change in the strength of the western boundary current. Corresponding to the anomalies of the summer monsoon, the upper layer circulation shows changes not only in magnitude, but also in structure from the climatology. The changes of the structure lie in the bifurcation of the western boundary current.

Keywords:

• interannual variation
• numerical modeling

Acknowledgements

This study is supported by programs under contract No. 2011CB403502, NCET-08-0510 and 201105002-11.