North–South Discrepancy of Interannual Sea Surface Temperature Anomalies over the South China Sea Associated with Eastern Pacific El Niño Events in the Spring

Yujie Liu,Shuang Li

doi:10.3390/atmos11101135

Abstract

This paper discovers a spatial feature of interannual sea surface temperature (SST) anomalies over the South China Sea (SCS) in the boreal spring, based on the Simple Ocean Data Assimilation (SODA) monthly data in the period from January 1958 to December 2010. The Empirical Orthogonal Function (EOF) analysis of interannual SST anomalies shows a north–south discrepant pattern of the first mode, which is characterized by higher (lower) anomalies in the northern (southern) SCS and possessing seasonal phase locking (in the boreal spring). Besides, the high correlation coefficient between the time series of the first EOF mode and the Nino 3 SST anomalies during winter reveals that this discrepant pattern is likely caused by El Niño events. The composites of SST anomalies show that this discrepant pattern appears in the eastern Pacific (EP) El Niño events, while it does not exist in the Central Pacific (CP) El Niño events. It is believed that the western North Pacific anticyclone (WNPA) plays a key role in conveying the El Niño impact on the interannual variabilities of SCS SST in the EP El Niño events. The anomalous anticyclone in the Philippine Sea weakens the northeasterly monsoon over the SCS by its southwest portion during the mature phases of the EP El Niño events. This anomalous atmospheric circulation contributes to the north–south discrepant pattern of the wind stress anomalies over the SCS in the EP El Niño mature winters, and then leads to the north–south dipole pattern of the contemporaneous latent heat flux anomalies. The latent heat flux is a major contributor to the surface net heat flux, and heat budget analysis shows that the net heat flux is the major contributor to the SCS SST anomalies during the spring for the EP El Niño events, and the north–south discrepancy of SCS SST anomalies in the succeeding spring is ultimately formed.

Highlights

The South China Sea (SCS) is one of the largest marginal seas of the western Pacific Ocean
Previous research focused on the response of the sea surface temperature (SST) anomalies over the whole SCS basin to El Niño–Southern Oscillation (ENSO), but the present paper notices the spatial distribution of the response within the SCS basin
Both of their first Empirical Orthogonal Function (EOF) modes show north–south discrepancy, and the time series are highly related to the Nino 3 Index

Summary

Introduction

The South China Sea (SCS) is one of the largest marginal seas of the western Pacific Ocean. It is a semi-closed deep basin and embraced by the Asian continent, the Indo-China Peninsula, the Kalimantan, the Philippines and the Taiwan Island. It connects with the Pacific, East China Sea, and Sulu Sea through the Luzon Strait, Taiwan Strait, and Mindoro Strait, respectively (Figure 1). The SCS is dominated by the northeasterly monsoon, while by the southwesterly monsoon during the boreal summer. It is widely recognized that the climate of the SCS has a strong relationship with El Niño–Southern Oscillation (ENSO) [4,5,6,7,8,9,10]

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Discussion

Conclusion