Abstract

Abstract. In this study we use the National Centers for Environmental Prediction (NCEP) monthly sea surface temperature (SST) fields (1982-1994) to investigate the temporal and spatial wriabilities of the South China Sea (SCS) warm/cool anomalies. Three steps of analysis were performed on the data set: ensemble mean (T), composite analysis to obtain the monthly mean anomaly relative to the ensemble mean (T), and empirical orthogonal function (EOF) analysis on the residue data relative to (T) +(T). The ensemble mean SST field (T) has a rather weak horizontal gradient: 29øC near the Borneo co•st to 25ø-26øC near the southeast Chin • coast. Two areas of evident SST anomalies were found in the monthly T variation: west of Borneo-Palawan Islands (WBP) and southeast of the southern Vietnam coast (SVC). Four patterns, monsoon and transition each with two out-of-phase structures, were found. During the spring-to-summer transition (March to May) the warm anomaly is formed in the northern SCS with T> 1.8øC located at 112ø-119ø30•E, 15ø-19ø30•N. During the fMl-to-winter transition (October to November) the northern SCS (north of 12øN) cool anomaly is formed in November with T <-0.6øC located at 108ø-115øE, 13ø-20øN. We performed an EOF analysis on the residue data relative to T + T in order to obtain transient and interannual variations of the SST fields. EOF1 accounts for 47 % of the variance and represents the northern SCS warm/cool anomaly pattern. EOF2 accounts for 14 % of the variance and represents the southern SCS dipole pattern. Strong northern SCS w•rm •nomMy (IøC w•rmer) •ppe•rs during October-November 1987 •nd J•nu•ry-February 1988, and strong northern SCS cool anomaly (IøC cooler) occurs during March 1986 and November 1992. Furthermore, • strong cross correlation between wind stress curl and SST anomalies, computed from the European Centre for Medium-Range Weather Forecast analyzed wind stress data and the N CEP SST 'data for different lags, shows the existence of an air-sea feedback mechanism in the SCS deep basin. 1.