The Inter-annual Variation of the Significant Wave Height in the South China Sea and Western North Pacific region

The variability of sea surface wave, which influences the energy flux exchange between air and sea and the upper ocean mixing, is an important part of the global climate change. A 34-year wind and wave dataset, which is obtained by a coupled air-sea model and WAVEWATCH III model, is used to investigate the inter-annual variation of sea surface wave in the Western North Pacific and South China Sea (WNP-SCS) region. With the empirical orthogonal function (EOF) analysis of the significant wave height (SWH) in summer (June-August, JJA) and winter (December-February next year, DJF), the main forcing factors of the variation are found. In winter, the first two leading principal components (PC) of SWH variations (accounting for 60.01%) are mainly associated with the variation of El Niño~Southern Oscillation (ENSO) on inter-annual time scale (PC-1, 40.63%) and the variation of Aleutian Low (AL) on decadal time scale (PC-2, 19.62%), respectively. In summer, the first leading PC explains more than 60% of the variation and the corresponding time series are significantly associated with the activity of tropical cyclones (TCs) and South China Sea summer monsoon (SCSSM). Based on the results of EOF and the further rotated EOF analysis, the variation of East Asia monsoon controls the variation of wave height in both winter and summer in SCS and in winter in WNP, while the activity of TCs dominates in summer in WNP.