Estimation of Initial Field in the Bohai Sea with the Adjoint Method: A Comparative Study on Optimization Algorithms

The adjoint assimilation technique is used to invert the prescribed initial field in the Bohai Sea. Based on this technique, the practical performances of the limited-memory BFGS (L-BFGS) method, the Regularization method, and the Gradient Descent (GD) method are investigated computationally through a series experiments. Experimental results demonstrate that the prescribed initial field can be successfully estimated by these three methods. Inversion result with the Regularization method is better than that with the L-BFGS method, although errors of observations are higher. Though higher simulation errors than L-BFGS and Regularization method, the difference between the prescribed distribution and inversion result is the lowest, indicating that inversion result with the traditional GD method is the best.