Coupled seasonal variability in the South China Sea
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ORIGINAL ARTICLE
Coupled seasonal variability in the South China Sea Zhuoqi He • Renguang Wu
Received: 25 July 2012 / Revised: 8 October 2012 / Accepted: 8 November 2012 / Published online: 28 November 2012 Ó The Oceanographic Society of Japan and Springer Japan 2012
Abstract The present study documents the relationship between seasonal variations in sea surface temperature (SST) and precipitation in the South China Sea (SCS) region. There are strong interactions between the atmosphere and ocean in the seasonal variations of SST and precipitation. During the transition to warm and cold seasons, the SST tendency is primarily contributed by net heat flux dominated by shortwave radiation and latent heat flux with a complementary contribution from ocean advection and upwelling. The contribution of wind-driven oceanic processes depends on the region and is more important in the northern SCS than in the southern SCS. During warm and cold seasons, local SST forcing contributes to regional precipitation by modulating the atmospheric stability and lower-level moisture convergence. The SST difference between the SCS and the western North Pacific influences the convection over the SCS through its modulation of the circulation pattern. Keywords Seasonal variability The South China Sea Atmosphere–ocean interaction
Z. He Institute of Space and Earth Information Science, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong R. Wu (&) Institute of Space and Earth Information Science and Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong e-mail: [email protected]
1 Introduction Extending from the equator to 23°N and from 99°E to 121°E, the South China Sea (SCS) is the largest marginal sea in the western North Pacific, surrounded by two continental shelves shallower than 100 m in depth (Wyrtki 1961; Shaw and Chao 1994). The SCS is a semi-enclosed basin with a mean depth of 1800 m and a maximum depth of 5400 m in the central basin (Twigt et al. 2007). As a part of the eastern Indian Ocean–western Pacific warm pool, the SCS displays remarkable air–sea interaction (Wang et al. 1997; Wu and Wang 2001; Liu et al. 2004; Xie et al. 2007; Wu 2010). For example, the East Asian winter monsoon activities can induce sea surface temperature (SST) anomalies that may last to summer and thus contribute to the year-to-year change in the East Asian summer monsoon (Chen et al. 2000; Chen 2002). Understanding the coupled variability in the SCS and its roles in regional climate is critical for regional climate prediction and climate-related risk management. The SCS is influenced by monsoon systems. The surface circulation in the SCS is primarily driven by monsoonal winds and the non-uniform wind distribution leads to the formation of multiple circulation centers (Wyrtki 1961; Shaw and Chao 1994; Chu et al. 1999; Hu et al. 2000; Liu et al. 2001a, b; Centurioni et al. 2009). During the winter monsoon period, a cyclonic gyre circulation in the central basin with a strong southward west
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