Seasonal variability in coastal fronts and its influence on sea surface wind in the Northern South China Sea

Abstract

High-resolution reanalysis data of Sea Surface Temperature (SST) show pronounced seasonal variations in oceanic fronts in the coastal area of the Northern South China Sea (NSCS), which are accompanied by the seasonality of monsoons. The NSCS oceanic fronts cover a wider area of the coastal sea in winter than in summer as strong winter monsoons progress. Nonetheless, the average SST gradients of the frontal area in both seasons are comparable. The response of surface wind to SST perturbations attributed to oceanic fronts in the NSCS coastal area has also been investigated by the observation data of satellite borne scatterometers and the simulation data of the Weather Research and Forecasting (WRF) model. Both the satellite observations and the simulations of the WRF model show apparent positive linear SST-wind coupling for most months in 2008, indicating the local influence of coastal SST fronts on the sea surface wind in the NSCS. The SST-wind coupling coefficients in the NSCS coastal sea are larger than those observed at mid-latitude oceans but smaller than those observed near equatorial oceans. It is also found that the influence of topography on the sea surface wind could be more important than that of the SST front at the southern end of the Taiwan Strait in winter. The transition of the monsoon could also affect the SST-wind coupling in the NSCS.