Semidiurnal radiational tides along the coasts of China

An improved procedure for extracting the radiational S2 tide from analyzed S2 is presented in this paper. The major improvement is that the nonlinear constituents are eliminated from the analyzed principal semidiurnal tides on the basis of the 'credo of smoothness' of admittance before using the procedure given by Zetler. The semidiurnal radiationai S2 tides for 42 stations along China's coasts are calculated using the method presented in this paper, and, for comparison, the results from Zetler's method are also given. In addition, the radiational S2 tides for 10 stations are analyzed with the response method. The results show that the mean amplitude ratio (radiational to gravitational) is 0. 17, the mean phase difference (radiational minus gravitational) is 119° for China's coasts.

Observation of Internal Tides in the Qiongzhou Strait by Coastal Acoustic Tomography

In this study,power spectral density and inverse analyses were performed to obtain the frequency characteristics and spatial distribution of temperature in the Qiongzhou Strait using reciprocal sound transmission data obtained in a coastal acoustic tomo-graphy experiment conducted in 2013.The results reveal three dominant types of internal tides(diurnal,semidiurnal,and terdiurnal).Spectral analysis of the range-average temperature deviation along the northern and southern transmission paths shows that along the northern path,the energy of the diurnal internal tides was significantly larger than that of the semidiurnal tides.The semidiurnal internal tides,in contrast,were more pronounced along the southern path.A terdiurnal spectrum with an energy level equivalent to that of the semidiurnal internal tide was discernable for both the northern and southern paths.These three types of internal tides can also be recognized in the time variation of the zonal-average temperature deviation.The diurnal internal tides were strengthened along the northern coast,implying their westward propagation and the existence of coastally trapped effects.The other two types of internal tides,which have smaller wavelengths than the diurnal internal tides,were less resolved over the entire tomographic domain due to the insufficient resolution of the inversion.The data quality was verified to be satisfactory by error estimation.

Two Ocean Tides per Day: Why?

Ocean semi-diurnal tides are suggested qualitatively to be more accurately explained by the vertical tide generating forces of the sun and moon, not by the historically standard horizontal components. It is proposed that the sea level elevations created sequentially at the eastern and then western ocean coastal boundaries propagate seaward as shallow water surface gravity waves and interact without mutual disturbance. In that manner two tides per day are created. Horizontal tide forces generate horizontal ocean currents with speeds of 5 mph at the most. Shallow water tide waves move at about 500 mph in open waters and therefore come much closer to being in tune with the sun and moon transiting across the sky.