Modelling of sea surface current and cirulation from satellite altimetry and ancillary data

Abstract

Altimeter data from Jason-1 satellite are very useful in providing general and continuous information about the ocean, including sea surface currents. The main objective of study is to identify the most appropriate mathematical equation for determining sea surface current in the South China Sea. The seasonal changes of surface current during different monsoon periods in 2004 and 2005 were also identified. The equations used to derive sea surface current are geostrophic current equations, wind-driven current equations and tidal current equations. The methodology of this study involves the use of sea level height and sea surface wind speed data from Jason-1 satellite altimeter to derive geostrophic current and wind-driven current. Tidal amplitudes from co-tidal charts were used to derive tidal current. The derived surface currents were used to produce combined geostrophic and wind-driven current. Combined geostrophic and tidal current as well as total surface current which is the combination of geostrophic current, wind-driven current and tidal current were also derived. Maps of total surface current circulation pattern were produced during four monsoon periods in 2004 and 2005. Regression analysis and comparison of mean and standard deviation values with sea truth data were carried out to identify the most appropriate equation of surface current for the South China Sea. Results of the analysis indicate that total surface current speed and direction have good correlation with the sea truth data, that is 0.68 and 0.70 respectively. The analysis by comparing the mean values indicate that there are no significant difference between the means of total surface current and the means of sea truth data. The standard deviations of total surface current are smaller compared to the sea truth data values. In conclusion, altimeter data from Jason-1 satellite combined with tidal data to derive the total surface current is appropriate to determine sea surface current circulation pattern in the South China Sea.