北印度洋半日潮波的数值模拟研究

基于FVCOM(Finite Volume Coast and Ocean Model)模型,建立北印度洋海域(31^°~102^°E,16^°S~31^°N)的M₂和S₂分潮潮波数值模式,研究北印度洋半日潮潮汐、潮流分布特征。对底摩擦系数进行数值试验,利用代价函数梯度下降法,得到分潮调和常数向量均方根偏差(RMSE)的变化曲线,逼近并确定最优的底摩擦系数。将采用该系数的模拟结果与TOPEX/Poseidon卫星高度计交叉点的调和常数数据、国际海道测量组织(IHO)及部分文献中的验潮站数据进行比较与验证,一致性较好。其中对比卫星数据的振幅偏差为2~4 cm、迟角偏差为7^°~8^°,与验潮站数据的振幅偏差为3~6 cm、迟角偏差为8^°~9^°。根据模拟结果,分析了北印度洋海域M₂和S₂分潮潮波传播特征和潮流椭圆的空间分布特征等。M₂分潮潮波在阿拉伯海南部有1个无潮点,在波斯湾内有2个无潮点,最大振幅超过80 cm;潮流在西北印度洋和孟加拉湾中部大多为顺时针旋转,其余海域大多为逆时针旋转;流速在阿拉伯海东北部、安达曼海、波斯湾和孟加拉湾北部较大,最大流速为160 cm/s,其他海域较小。S₂分潮的潮波传播特征、无潮点的位置和潮流椭圆的空间分布特征等都与M₂分潮类似,但潮波振幅和潮流流速等都相对M₂分潮较小。研究完善了北印度洋海域2个主要半日分潮M₂和S₂的整体特征。

Numerical Simulation of Semi-diurnal Tidal Waves in the Northern Indian Ocean

Based on the Finite Volume Coast and Ocean Model (FVCOM ), a numerical model for M₂ and S₂ tidal waves in the Northern Indian Ocean (from 31^°E to 102^°E, from 16^°S to 31^°N) is established, and the characteristics of Semi-diurnal tides and tidal currents are investigated. We carried out a numerical test on the coefficient of bottom friction by using cost function gradient descent method, in which the change curve of root mean square errors (RMSE) of tidal constituent harmonic constant vector is obtained and optimal bottom friction coefficient is thus determined. Simulation results based on the optimal coefficient are compared and verified with the harmonic constants at the satellite altimeter intersection points of TOPEX/Poseidon, provided by the International Hydrographic Organization (IHO), and measured at tidal gauge stations, and the results are in good agreement with the observational data. It shows that the deviation of the simulated amplitude is from 2 cm to 4 cm and that of phase-lag is about from 7^° to 8^° whenc ompared with the T/P data; the deviation of amplitude is about from 3 cm to 6 cm and that of phase-lag is about from 8^° to 9^° when compared with the tide station data. We also analyzed M₂ and S₂ tidal propagation characteristics and spatial distribution of tidal ellipses in the region, and found that the M₂ tidal constituent has an amphidromic point in the southern Arabian Sea and two amphidromic points in the Persian Gulf, with maximum amplitude exceeding 80 cm, and the tidal current is mostly clockwise in the northwest Indian Ocean and central Bay of Bengal. The tidal current velocity is larger in the northeast of the Arabian Sea, the Andaman Sea, the Persian Gulf and the northern part of the Bay of Bengal, with maximum velocity of 160 cm/s. Tidal wave propagation characteristics, location of amphidromic point, and spatial distribution of tidal ellipse of S₂ are similar to those of M₂, but tidal wave amplitude and tidal current velocity of S₂ are relatively smaller than those of M₂.