Inversion of two-dimensional tidal open boundary conditions of M2 constituent in the Bohai and Yellow Seas

Two-dimensional tidal open boundary conditions of the M₂ constituent in the Bohai and Yellow Seas (BYS) have been estimated by assimilating T/P altimeter data. During inversion, independent point (IP) strategy was used, in which several IPs on the open boundary is assumed, values at these IPs can be optimized with an adjoint method, and those at other grid points are determined by linearly interpolating the values at IPs. The reasonability and feasibility of the model are tested by ideal twin experiments. In the practical experiment (PE) after assimilation, the cost function may reach 1% or less of its initial value. Mean absolute errors in amplitude and phase can be less than 5 cm and 5°, respectively, and the obtained co-chart can show the character of the M₂ constituent in the BYS. The results of the PE indicate that using only two IPs on the open boundary can yield better simulated results.