The deep basin occupies 44% of the total area of the SCS. The hydrology of the SCS is deeply influenced by the Southeast Asian monsoon system. Dynamic characteristics in the SCS have been investigated by previous studies [1-4] can be primarily summarized as: (1) the 1|]# circulation driven by seasonal monsoon induce basically a cyclonic gyre in winter and an anticyclonic gyre in summer. (2) Cyclonic eddy located Inhibitors,Modulators,Libraries at off west Luzon in winter and a dipole structure with a coastal jet off east Vietnam in summer. (3) El Ni?o events affect the wind field and influence the circulation eventually. As a part of the western Pacific warm pool, SCS plays a major role in hydrology and climatology to the surrounding areas .
The sea surface temperature (SST) is a major signature of upper ocean thermal processes.
It is affected by upper layer variability to a large extent. On the other hand, the sea surface height (SSH) as an integrated response of the entire water column primarily reflects ocean Inhibitors,Modulators,Libraries dynamic variability. Thus, Inhibitors,Modulators,Libraries assuming a constant salinity over the upper layer in the SCS, the change in SSH should follow the heat input. In other words, SSH may record the Inhibitors,Modulators,Libraries thermal input into the ocean in ignoring the dynamic processes.Satellite altimeter data has provided an opportunity to derive a good quality SSH dataset . The estimates of upper layer thickness (ULT) from satellite altimeter data have also been studied since 1990s. Shay et al.
 using satellite altimeter and SST data as input to a two-layer reduced gravity model, Inhibitors,Modulators,Libraries one can obtain a first order approximation of the upper layer thermal structure.
Goni et al.  estimated the ULT in the southwestern Atlantic Ocean from Geosat altimeter data and fitted fairly well Inhibitors,Modulators,Libraries to the results of inverted echo sounder. Garzoli et al.  used the altimeter data derived ULT to monitor the upper layer transport in the southeastern GSK-3 Atlantic Ocean. Pun et al.  used altimeter derived ULT to improve Inhibitors,Modulators,Libraries typhoon intensity forecast in the Western North Pacific Ocean. The spatial and temporal variability of the split of Kuroshio extension was also studied by using the altimeter data derived ULT . A further application of altimeter data derived ULT is to study the heat storage in the upper layer combined with sea surface temperature [13-16].
The applications of satellite derived sellekchem ULT are most in the open oceans; however, in this study we validate the usability of this estimation Inhibitors,Modulators,Libraries in a semi-closed sea. The spatial and temporal variability of ULT is also investigated. The study area is from 5��N to 23��N and from 108��E to 121��E Dacomitinib covering most of the deep basin of the SCS as shown in Figure 1a. This paper is organized as follows. In section 2, the data and data processing are introduced. Section 3 provides a two two-layer reduced gravity ocean model for estimating ULT. selleckchem The ULT derived from satellite altimeter data is validated in section 4.