Authors: Xu Ming and Vivien P. Chua
The circulation in Singapore coastal waters is driven by the variable tidal forcing of the surrounding seas, complex bathymetry, irregular coastlines, seasonal monsoons and local winds. An unstructured-grid SUNTANS model, with an average resolution of 100 – 200 m around Singapore, is applied to Singapore coastal waters. The model is tidally forced at the three open boundaries, located to the west, south and east of Singapore, using the 8 main tidal constituents as derived from the OSU Tidal Prediction Software (OTPS). It is also forced by hourly National Climate Data Center (NCDC) observed wind data at 59 stations throughout model domain. Our calibration results show that the model accurately predicts sea surface elevations and currents at several locations throughout the model domain. Volume transport in Singapore coastal waters is investigated with the calibrated model. To examine the effects of tidal and wind forcing on volume transport, a new decomposition method is proposed. It is found that: (1) tidal forcing is the predominant factor that drives volume transport in Singapore coastal waters; (2) wind forcing affects volume transport in Singapore coastal waters, especially during monsoon seasons; and (3) the residual effects, which can be attributed to the nonlinear interaction between tidal and wind forcing, tend to reduce the total volume transport and are stronger during the Southwest monsoon season.
Keywords: Singapore coastal waters, numerical model, unstructured-grid, tidal forcing, wind forcing, volume transport