西沙群岛潮、余流特征研究

对1962、1974、1976、1991、2002年西沙群岛海域实测海流资料分析得出:西沙群岛潮汐特征系数为3.40,是不正规日潮;潮流特征比较复杂,少数为不规则半日潮流型,多数为不规则日潮流型;半日周期的内潮在永兴岛西部特别显著,最大流速可达1.5m/s,对珊瑚生态系统有重要影响;西沙群岛余流,春季4～5月总体方向是东北,最大余流速度66cm/s,出现在中建岛西部;夏初余流方向偏北,速度明显降低,中建岛表、底层流速都不超过50cm/s。结合18a卫星高度计资料统计分析得出,春季和夏季西沙群岛海域处于反气旋式环流的北部,中建岛处于反气旋式环流的西缘,水平压强梯度大,加之地形影响,因此流速最大。

Study on Features of Tide and Residual Currents in the Region of Paracel Islands

By analysis of actual measurement data in 1962、1974、1976、1991、2002 in the region of Paracel Islands,we draw some conclusions as follows: Tidal characteristic coefficient in this area is 3.40,it is irregular diurnal tide.The features of tidal current are complex,minority of them are irregular semi-diurnal tides while the majority are irregular diurnal tides.The internal tides of semi-diurnal periods are extremely significant in western parts of Yongxing Island,the maximum speed can reach 1.5 m/s,which has an important influence on carol ecosystems.The residual currents in April and May mainly directs northeast,and the maximum residual current speed is 66cm/s which occurs in western parts of Zhongjian Island.At the beginning of summer,the residual currents directs north and the speed significantly reduces,the surface and bottom speeds of Zhongjian Island are less than 50 cm/s.Statistical analysis of 18-year satellite altimeter data show that Paracel Islands are located at the northwest parts of anticyclone circulation in this area and Zhongjian Island is located at the western edge of anticyclone circulation.The maximum speed apears around Zhongjian Island under influence of maximum sea surface pressure gradient and topography effect.