South China Sea Warm Pool Detected in Spring from the Navy’s Master Oceanographic Observational Data Set (MOODS

Abstract. A South China Sea warm pool with sea surface temperature (SST) higher than 29.5øC, recently reported by Chu and Chang [1995a, b] and Chu et al. [1997], appears in the central South China Sea (west of the Luzon Island) in boreal spring, strengthens until the onset of the summer monsoon (mid-May), and then weakens and disappears at the end of May. The transient features and interannual variabilities of the warm pool have not yet been studied. Here we use a subset of the U.S. Navy's Master Oceanographic Observation Data Set (MOODS) to investigate the surface thermal features. First, we employed an optimal interpolation scheme to build up a 10-day interval synoptic data set for December 1963 to November 1984 on a 0.5øx 1 ø grids (finer resolution in zonal direction) from the MOODS SST data. An ensemble mean SST field (T) was established with a rather weak horizontal gradient (28.5øC near the Palawan Island to 26øC near the southeast China coast). Second, we performed a composite analysis to obtain the averaged SST anomaly field T deviating from the ensemble mean for the winter and spring seasons (December-May). During December-March, T is negative almost everywhere throughout th