Shallow water tides induced by frictional nonlinearity in the Bohai and Yellow Seas

Abstract

In shallow waters, tidal friction at seabed is proportional to the square of tidal current velocity, and can induce shallow water tides. M2, S2 and N2 are the most important semi-diurnal constituents in the Bohai and Yellow Seas, and their interaction through the frictional nonlinearity can induce shallow water tides, with 2MS2 and 2MN2 being the most representative constituents. In this paper, we analyze the observed hourly records at 27 tidal stations along the coast of the Bohai and Yellow Seas and obtain harmonic constants of μ2 and L2 constituents, which can be separated into astronomical parts μ2′ and L2′, and frictional nonlinearity-induced parts, 2MS2 and 2MN2, respectively. A numerical model is also performed to simulate the constituents 2MS2 and 2MN2. It shows a fairly good agreement between the model and observations in the harmonic constants of constituents 2MS2 and 2MN2. The cotidal charts of 2MS2 and 2MN2 are presented. It is found that the frictional nonlinearity-induced shallow water tides can significantly reduce the main fortnightly and monthly modulations.