Finally, a summary is given in section 6.Figure 1.(a) Bottom topography (b) in-situ measurements station distribution from 1980 to 2005 in the South China Sea. Region with water depth shallower than 200 m is stripped. Numbers on isobaths show the water depths in meter.2.?Data and Data ProcessingTOPEX/Poseidon (T/P) and Jason-1 altimeter data used in this study is processed and provided by the National Aeronautics and Space Administration (NASA) Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory (JPL), California Institute of Technology. The precision of the T/P altimeter system is on the order of 4 cm for each measurement [8, 18, 19]. The Jason-1 satellite was launched to extend the long-term success of T/P oceanographic mission. This provides an extended continuous time series of high-www.selleckchem.com/products/Sorafenib-Tosylate.html accuracy measurements of the ocean surface topography from which scientists can detect the Earth’s climate change. The accuracy of sea level anomalies can be as high as 2.5 cm or better [20]. The data have been corrected for the effects of the following: troposphere, ionosphere, inverse barometer, sea state bias, and tides. The T/P and Jason-1 altimeter data along the tracks within our study area from 1993 to 2005 constitutes a baseline for this study. We computed the collinear residual SSH to remove the unknown geoid, which is time invariant, and removed a nine-year mean from 1993 to 2001. The products are defined as sea surface height anomaly (SSHA) data [21]. Accordingly, the average SSH is computed to 1�� latitude by 1�� longitude grid with one month resolution after interpolations.The in-situ hydrographic data (World Ocean Database 2005) used in this study are provided by the National Oceanographic Data Center (NODC) of National Oceanic and Atmospheric Administration (NOAA). The data consist of hydrographic parameters collected from hydrographic casts including conductivity-temperature-depth (CTD) probes, bottle low resolution CTD, mechanical expendable (XBT), digital bathythermographs, profiling float, autonomous pinniped bathythermograph data, drifting buoy data, moored buoy data and undulating oceanographic recorder data [17]. We process the data to generate monthly and 2�� latitude by 2�� longitude grid data sets. The standard deviation check is used to remove the outliers. This means that the data points being more than three standard deviations apart from the mean are removed. These data points are considered as being affected by transient effects of waves, strong winds, or other dynamic processes. After data processing, about thirty million hydrographic profiles from January 1980 through December 2005 are obtained. Their distribution is shown in Figure 1b. The main limitation of this kind of in-situ measurements is its uneven distribution in time and space. Certain periods and areas are over sampled, while others are under.