基于浮标站观测的磨刀门洪枯季径潮动力作用规律及相关性分析

Action law and correlation analysis of river-tide dynamics during flood and dry season in Modaomen based on buoy stations observation

为揭示磨刀门主要动力因子对潮流运动的作用规律,采用主潮通量算法计算洪枯季半月不同时间尺度下的潮流动力特征值,采用多元线性回归法对特征值的相关性进行拟合分析。结果表明,磨刀门水道内平均落潮流速洪季比枯季总体大约14%,但涨潮平均流速仅为枯季一半;水道内洪季余流流速很大,枯季可忽略不计;口门外东汊和西汊涨潮流态洪季存在相互顶托,枯季均为西南向,洪枯季余流流速西汊均大于东汊,近底层水深范围存在逆时针半环流结构,且枯季尤为明显。潮汐动力和海面风对水道内余流影响较小,径流动力洪季影响显著、枯季影响很小。由于洪季径流动力强劲,东汊和西汊净潮通量变化规律一致;枯季磨刀门水道净通量主要输运至东汊水域,随沿岸流朝西南方向输运进入西汊,然后随离岸流朝南侧外海方向输出,符合口门外逆时针半环流结构的输运特征。

To reveal the effect on tidal flowing by main dynamic factors in the Modaomen estuary,we use a method of main tidal flux algorithm to calculate characteristics of tidal flowing under different time scales in half month of flood and dry seasons,and apply the method of multiple linear regression to fit their correlation.The results show that vertical averaged velocities during ebb period in Modaomen waterway in flood season is about 14%higher than those in dry season,and only about half of those during flood period.Residual velocities in the waterway during flood season are rather large and can be ignored during dry season.There is mutual collision of rising currents between the east and west branches outside the estuary of the waterway during flood season,while both point to the direction of southwest during dry season,and residual velocities in the west branch are more than those in the east constantly.Regardless of seasons,there is a counterclockwise semi-circular flowing structure close to seabed outside the estuary,more apparently during dry season.The impact of tidal power and wind on residual currents in the waterway are small,while runoff power takes position during flood season and ignored during dry season.The runoff power is strong during flood season,and the tidal fluxes of the east branch and the west branch are consistent.During dry season,net tidal flux from the waterway is mainly transported to the east branch,following southwest coastal current and entering the western branch,and then is exported towards the south of outer sea with offshore tidal current,which is consistent with the structural characteristics of the counterclockwise semi-circulation outside during dry season.