Author(s): H. Gerritsen; E. J. O. Schrama; H. F. P. Van Den Boogaard
Linked Author(s):
Keywords: Barotropic tidal models; Tidal modelling; Altimeter data; Adjoint modeling; Modelcalibration
Abstract: Focusing on depth-integrated numerical modelling of barotropic tides in the South China Sea and the seas of the Indonesian Archipelago, the tidal representation of a limited area tidal model was analysed and validated in two steps. First, TOPEX-POSEIDON altimeter data at track cross over points was introduced as offshore tidal information to complement the common four-constituent in-situ tidal data. The altimeter data provided five additional tidal constituents for the modelling, and indicated the need for adjustment of the open ocean tidal forcing of the South China Sea. Subsequently this led to a significantly improved tidal representation in the deeper parts of the model. Using the new model representation as starting point, the adjoint technique was used to perform a sensitivity analysis on the model, focusing on the shallower parts, to improve and validate these in a quantitative and objective way. The parameters considered represent the specification of the tidal components at the open boundaries, the depth in the shallow regions and the bed friction coefficient. The tidal behaviour was again found to depend strongly on the tidal specification at the open boundaries, while subsequently it showed much less sensitivity to the depth and bed friction used. It is concluded that the use of tidal information from altimetry, together with model calibration using an adjoint modelling technique, leads to quantitative insight in model behaviour and provides a structured approach to model validation.
Year: 2003