The Monsoon-ocean Coupled Modes In The South China Sea And Their Relationship With Monsoonal Precipitation

This study examined the regional monsoon-ocean coupled modes (MOCM) in the South China Sea (SCS) at different time-scales and their relationship with the monsoonal precipitation, based on the 1948-2005 NCEP/NCAR reanalysis data of sea surface temperature (SST) and wind filed (include zonal wind U and meridional wind V) at 10m level over sea surface. Two developed singular value decomposition (SVD) was employed to abstract the coupled information of the ocean-atmosphere interaction, namely as the U-V combinated SVD (CSVD) and the season-reliant SVD (S-SVD).It was found that there are obvious multi-scale temporal and spatial characteristics in the MOCMs of the SCS. For the annual cycle variability, the leading mode of the MOCM derived from CSVD on SST and surface wind fields displays a consistant positive correlation pattern with an ellipse-shape for SST, which represents the warm water distribution in summer, and a typical summer-monsoon pattern for surface wind in homogeneous and heterogeneous correlation fileds. The time series of the leading CSVD mode shows a single-peak structure and the mode correlation coefficient exceeds 0.9 that indicate there is typical monsoon-ocean interaction in the annual cycle of the SCS.At the timescale of intraseasonal variability with a period of 90-120 days, the leading CSVD mode and the second mode mainly display the pattern that the summer-monsoon has been break out and the intraseasonal oscillation propogate north-southward. The third mode shows the summer-monsoon break out late. At the timescale of Madden-Julian oscillation (MJO) with a period of 30-60 days, the leading mode displays the winter-monsoon pattern, and the second and the third mode mostly represent the summer-monsoon pattern. All of the three modes show obviously oscillation in former semi-year, especially about the period of the monsoon breaking out. It indicates that the monsoon-ocean coupled mode is stronger in winter, spring and early summer, and maybe a trigger for the SCS summer-monsoon onset.At the interannual and decadal time scales, the time series of the leading mode...