The Harmonic Analysis Method For Non-regular Sampled Data And Its Application On Water Exchange In The Mouth Of Jiaozhou Bay

A harmonic analysis method for non-regular sampled data is developed, and the method is implemented with Matlab internal functions used. It has the advantages of analyzing discontinuous tides and tidal currents data whose intervals are variational, and the harmonic constants can be acquired. With the method, sampled observational data of different tide station which have equal time intervals and non-equal time intervals are analyzed, and the results are compared with that of traditional method. It shows good conformity, for the main O₁,K₁,M₂ and S₂ constituents, the difference of amplitude smaller than 2cm and the phase's difference smaller than 1°; If the tidal frequency is more than half of the sampling frequency, it will cause the frequency aliasing; There will be great error when the period of the constituent is larger than the sample length. As is shown, not only the method of tidal harmonic analysis can apply to non-regular sampled observational data, such as sampled observational data with non-equal time intervals, but also the precision can be the same as that of the traditional method, with more convenient, flexible and practicable to analyze the tidal data.The ship-mounted ADCP current data in Jiaozhou Bar was applied with the present method and the characteristics of water exchange are analyzed. The harmonic analysis involved O₁,K₁,M₂,S₂,M₄,MS₄ and M₆ constituents. The results shows that, maximum velocities of the M₂ constituent are between 50cm/s and 70cm/s, while that of the O₁,K₁,S₂,MS₄ and M₄ constituents are between 10cm/s and 20cm/s. The MS₄ and M₄ of the shallow water constituents are significant in Jiaozhou Bar. The M₆ constituent's maximum velocities are between 1cm/s and 10cm/s. Residual current in the mouth of Jiaozhou Bay flow in north and flow out south in general, and the residual current's velocities near Tuandao is larger than that near Xuejiadao with 45cm/s as its maximum velocity. The turning point of the residual current direction is 36.0329°N and 120.2869°E, which is near Tuandao.