Spatiotemporal Variability of Chlorophyll a and Sea Surface Temperature in the Northern South China Sea from 2002 to 2012

Abstract

Eleven-year time series data gathered by the moderate-resolution imaging spectroradiometer (MODIS) for chlorophyll-a (Chl-a) and sea surface temperature (SST) were collected. Empirical orthogonal function (EOF) decomposition and kriging interpolation were applied to capture the main variations of Chl-a and SST. The results showed that Chl-a and SST exhibited four basic patterns: (i) Chl-a and SST were relatively well correlated (R2 = 0.48) and had a converse season cycle. (ii) The coastal regions were characterized by high Chl-a concentrations and low SST, whereas the open sea area had relatively low Chl-a concentrations and high SST. (iii) Chl-a and SST showed a seasonal pattern for almost every category. In summer, Chl-a concentrations were relatively low (<0.2 mg·m−3) and SST was high (>27°C); in spring and autumn, Chl-a concentrations and SST were dominated by values of 0.1–0.2 mg·m−3 and 25–29°C, respectively; in winter, Chl-a concentrations were relatively high (0.2–0.4 mg·m−3), and SST was low (<27°C). (iv) The EOF mode for the variations in Chl-a and SST in the northern South China Sea (SCS) regions accounts for approximately two thirds of the total variance. This study demonstrated that the EOF could provide a preliminary quantification of synoptic Chl-a and SST distributions.