Abstract: Based on the simulation of the M₂ tide in the Bohai,Yellow and East China Seas,numerical experiments are made to study 4 strategies on the bottom friction coefficient(BFC) in a numerical adjoint model.In order to make a better simulation,the strategy must be consistent with the given BFC distribution.The real bottom friction decided by ocean topography is very complicated and an independent BFC is required.The fourth method which takes the BFC in each grid point as an independent BFC simulates practical experiments best and demonstrates the reasonability and efficiency of this method.

Key words: bottom friction coefficient, tidal model, adjoint assimilation method, inversion