涠洲岛海域潮流不对称的偏度判别研究

Quantifying Tidal Current Asymmetry in the Weizhou Island Zone Basing on the Skewness Method

关键词:  涠洲岛  潮流不对称  倍潮  偏度判别法

Key words:  Weizhou island  tidal current asymmetry  overtide  skewness method

摘要:

[目的]潮流不对称现象是潮波运动的基本特征之一,潮流不对称的量化及适用性是近海潮波动力学的重要研究内容。采用涠洲岛附近海域1988年10月6日~1989年3月9日实测的分层(10m、20m和30m)潮流数据对涠洲岛附近海域的潮流不对称现象进行研究。[方法]首先对实测资料进行调和分析得出余流及35个分潮,进而基于调和分析结果利用潮流不对称偏度判别法对实测潮流数据的潮流不对称进行计算。[结果]研究认为,在u方向(W-E),虽然垂向上流速大小有变化,但均为正向不对称,且其不对称程度基本相同。在v方向(N-S),10m层和20m层流速均为负向不对称,30m层呈正向不对称,三者在量值上由上层向下逐渐增大。在各层次各方向上,对潮流不对称贡献最大组合的均为余流及余流与分潮的相互作用,O1、M2和MO3分潮的相互作用以及K1、M2和MK3分潮的相互作用对潮流不对称的贡献亦不能忽略,其量值能达到甚至超过O1、K1、M2的贡献。潮波进入浅水发生变形,导致潮流不对称的影响因素在浅水和深水海域不同。[结论]涠洲岛附近海域潮流不对称具有明显的垂向变化,10m、20m层与30m呈现不同的不对称特征。潮流不对称偏度判别法在较深水海域同样具有适用性。

Abstract:

[Objective] Tidal current asymmetry is one of the fundamental characters and its quantification and application are important topics in the field of tidal dynamics.Measured tidal current of three layers(10m, 20m and 30m)from October 6, 1988 to March 9, 1989 was adopted to analysis the tidal current asymmetry in the Weizhou Island Zone.[Method] The residual current and 35 tidal constituents were obtained by harmonic analysis, then the tidal current asymmetry was computed through the skewness method.[Result] In u direction (W-E) tidal current asymmetry is positive and of almost constant degree though the amplitudes of tidal currents are vertically different.In v direction (N-S) tidal current in 10m-layer and 20m-layer is positive while it is negative in 30m-layer.The degree increased downward.The first contribution is residual current and the interaction between residual current and tidal constituents in each layer and each direction.The contributions of O1/M2/MO3 and K1/M2/MK3 are also unneglectable and their contribution maybe lager than that of O1/K1/M2 in some cases.[Conclusion] The distortion of tidal wave in shallow water is account for the different exhibition between shallow water and deep sea.