Ocean Modeling and Data Assimilation

The focus of the research is on the modeling of the ocean circulation in different domains of the South China Sea ( SCS ) with different scientific objectives. The model used is the Finite Volume Coastal Ocean Model (FVCOM) adapted to different configurations. The larger scale modeling covers the entire SCS and the scientific goal is to study the modes of oceanic climate variability associated with the Indonesian through-flow and the SCS through-flow, which is opposite to the former one and considerably reduces its volume and heat transports from the Pacific to the Indian ocean. Open boundaries data and surface wind and heat/moisture fluxes are provided by the MIT global ocean model for the years 1960 through 2000. The present focus is to establish the changes in sea surface temperature, heat content and circulation of the SCS between the decade of the 60s and the 90s, due to the considerable warming observed on the global scale both in the atmosphere and the ocean. These changes affect the temperature and properties of the waters in the Singapore Strait surrounding the island of Singapore. An example of the modeled surface circulation is given showing the wind-driven currents induced by the North-East monsoon (January-February) with the strong jet of Pacific waters entering the northern Luzon strait, spreading southward inside the SCS to exit in the Indonesian channels. Superimposed in color is the sea surface elevation.

The second focus of the research is also on the entire SCS but "zooming-in" the local domain covering the Singapore Strait (SS) itself. The scientific objective is to study the frequency and variability of storm surges events associated with both the North-East and South-West monsoons. The former ones induce even extreme sea level anomalies, up to 70 cm. high, in the SS, with consequent damaging effects on the shoreline of the island and the costal structures. The investigation is carried out both through extensive analysis of sea level data from all the tide gauges distributed all around the SCS and through modeling simulations. As an example, the sea level response is shown to the storm surge produced by the North-East monsoon, which induces a sea level as high as 1.2m in the Singapore Strait. The third type of simulations are carried out in very local configurations in the channels surrounding Singapore, where Professor Patrikalakis and his group have been carrying out extensive field work in January and June 2009. The focus of this work is the assimilation of the collected observations, such as surface drifters and AUV data, to reconstruct vortex and jet structures present in the channels. Data assimilation packages based on the Kalman filter method are available for FVCOM.