The Intrinsic Mode Of Continental Shelf Waves And The Forced Continental Waves In The East China Sea

Continental Shelf Waves (CSW) play an important role in understanding thedynamics of the continental shelf area. It is also of great significance for improvingthe prediction of the sea level and the alongshore current. Although studies on CSWstarted as early as1980s, the research on this topic is still quite rare, especially for thegeneration mechanism and application in sea level and alongshore current predictionin the East China Sea (ECS) which is one of the widest continental shelves in theworld.Based on analytical theory, numerical solution and data analysis, this workconfirms the existence of free and forced CSW in ECS. This low-frequency waveactivity is one of the most important dynamical processes in ECS.The dispersion relation in ECS is obtained which shows that there are a set oflow-frequency waves as different modes of CSW. The dispersion relation derivedfrom observation agrees quite well with the analytical results. Analytical theory andnumerical solution indicate that barotropic Kelvin wave plays the dominant role inECS, and the first (SW1) and second (SW2) modes of CSW Shelf Wave are alsoimportant.By employing the Empirical Mode Decomposition (EMD) scheme, we find thatCSW does exist in ECS, and the periods are from2to10days.The low-frequency sea level fluctuation is closely related with wind forcings.Large sea level rise always follows the strong north wind in ECS. The amplitude ofthe sea level variation can reach tens centimeters. Numerical solution indicates thatthe alongshore wind can induce a downwind alongshore current.The wind-forced CSW theory is applied in ECS. Numerical results show that the calculated results can successfully reproduce the sea level variation and downwindflow. The model can simulate alongshore current better than that of the sea level,because the sea level vaariation is mainly due to the Kelvin waves (KW) while thealongshore current is controlled by the Shelf Waves (SW1).The low-frequency fluctuation in ECS is mainly the free wave. And the freewave can be induced into force wave in the condition of strong alongshore wind.