Abstract:

Based on ocean surface currents observed by the High Frequency Ground Wave Radars (HFSWRs) from April 2019 to May 2020, the characteristics of tidal and residual currents in the central eastern sea area of Hainan Island were studied. The results show that the tide in the central eastern sea area of Hainan Island mainly belongs to the irregular semidiurnal tide. The movements of the semidiurnal tidal currents M₂ and S₂ are mainly in the form of reciprocating current, and the movements of the diurnal tidal currents O₁ and K₁ are mainly the form of clockwise rotary current. The spatially averaged amplitudes of M₂, S₂, O₁, and K₁ have a ratio of 1 : 0.51 : 0.60 : 0.65; and the semidiurnal tidal current M₂ is dominant among the four tidal current constituents. The probable maximum current velocities increase gradually from southwest to northeast, and the maximum is 35 cm·s^-1. Due to the influence of the East Asian monsoon, the residual currents have significant seasonal variation, with summer (from June to August), winter (from September to February of the following year) and transitional (from March to May) types. For the summer type, the directions of the residual currents are basically northeast, and the average velocity is 29 cm·s^-1. The residual currents of the winter type flow toward the southwest, and the average velocity is 36 cm·s^-1. Note that the residual currents of the winter type are greater than those of the summer type. The residual currents of the transitional type have complex directions, and the average velocity of 13 cm·s^-1. Overall, the southwest residual currents have the largest velocity and last the longest time during the year, and therefore the material transport in surface sea water is from northeast to southwest in the central eastern sea area of Hainan Island.

Key words: high frequency surface wave radar, surface current, tidal current, residual current