The spectrum analysis of tidal current and the study of residual current in summer in Xinhai Bay of Hainan Province

Based on the result of tidal current in the Xinhai area of Qiongzhou Strait, no matter f>0 or f<0, diurnal tidal spectrum peak is higher than the semidiurnal tidal spectrum peak. Among them, the cycles of semidiurnal tide are about 12.0 h and 12.4 h, and the cycles of diurnal tide are about 23.9 h and 25.8 h. In the component of diurnal and semidiurnal tide, the anti-clockwise component is the main component: clockwise diurnal spectrum is only 84% of anti-clockwise diurnal tidal energy spectrum; clockwise semidiurnal tidal energy spectrum is only 63% of anti-clockwise semidiurnal tidal energy spectrum. The main cycles of shallow-water tide are 8.3 h and 6.2 h, and others longer than one day, such as 4.2 d and 3 d, are also obvious, but they all don’t content significant test. The velocity of most residual currents ranges from 5 cm/s to 10 cm/s, some particulars are over 40 cm/s. Influenced by the anti-clockwise circulation movement, the main directions are in the range of NE,N and NW ,which make up more than 68% of the total observations. Wind also has significant effect: northeast wind will make direction of residual current to south, the north wind will make the direction of residual current to south.