Characteristics Of Seasonal And Interannual Variability Of The Thermal Structure In The Upper South China Sea

Oceans are the important part of the climate system, the most of the solar radiation absorded by oceans is stored in the surface oceans (mixed layer). The atmosphere is drived and climate is influenced by the energy. The variability of the thermal structure in the mixed layer plays a important role in the climate and atmospheric circulation. The ocean heat content is stabler than sea surface temperature (SST), and has more important affect. The SST of the coastal China seas can effect its area even the precipitation in the flood season in the interior. The variability of the heat content in the South China Sea can influence the East Asian monsoon and the anomalies of the climate. So the exploration of the heat content can make us understand the dynamic processes and the mechanism of the air-sea interaction easily, and the variability of the Asian monsoon and the prediction of Chinese climate can be understanded well.The assessment of CORA has benn done, indicating that CORA can represent more subtle features than SODA. Te seasonal and interannual variability of SST in the coastal China seas can be well portrayed by CORA data. The second mode of EOF reveals the SST response to wind-induced latent heat. The third mode presents the northeast-southwestern distribution of SST front, which is coincident to the transitionally seasonal characters between summer and winter, the interannual variability of SST is closely related to ENSO.Based on the TRMM/TMI satellite remote sensing data during1998to2010, the intra-seasonal variabilities of the SST in the South China Sea are analyzed, and the possible mechanism for generating the intra-seasonal SST variabilities is also discussed. Intraseasonal oscillation has closed relationship with zonal wind component, meridional wind stress and the latent heat flux. Based on SODA data, the characteristics of the seasonal and inter-annual variations of the mixed layer depth (MLD) in the South China Sea (SCS) are derived. Data analysis indicates that the monsoon has an obvious impact on the temporal and spatial features of the mixed layer in the SCS through the adjustment of the current field. The MLD of the SCS has a deepening trend in general; however the differences between northern and southern areas are obvious. The first mode shows that the variability is the same in the whole area of SCS basically.And the second mode shows that the variability is dipole-type. The trend of MLD in the SCS is different form north and south, from the Luzon Strait along the continental slope south of China is shallowing, and the other in the deep basin of the southern SCS is deppening.Analysis shows that heat content in SCS has obvious seasonal variation close to SST, Net surface heat flux also shows the same variation. Results of spectrum show that there is about29months period. The first EOF mode note that there is a local maximum positive value centered at the east off Vietnam, and a local maximum negative value located at the northwest off Luzon Strait and the most sensitive area to water exchange between the SCS and the western Pacific. The spatial pattern associated with the second EOF mode (EOF2) is positive over the center of SCS, other area is negative. It is found that the variability has a good correspondence with ENSO events. Interdecadal variations of the heat content in the SCS expressed as upward trend. Observational ocean temperature and salinity data are used to calculate volume transport, heat transport and Salinity transport across120°E sections. Base on the CORA data, the monthly and annual mean volume heat and salt transports through the open boundaries of the SCS are reported. The computation shows that the net volume, heat and salt transports of SCS is0.377Sv、0.1567Pw、-1.0635Gg/s respectively.