基于GOCI和FVCOM的黄河口切变锋特征与泥沙输运研究

Study on the Characteristics of Shear Front and Current Transport of Sediment in the Yellow River Estuary Based on GOCI and FVCOM

本文以黄河口切变锋为对象,基于静止轨道海洋水色成像仪(Geostationary Ocean Color Imager,GOCI)遥感数据和水沙观测数据,建立了高精度的渤海海表悬浮体浓度(Suspended Sediment Concentration,SSC)反演公式,采用最大互相关(Maximum Cross Correlation,MCC)法和SSC梯度相结合的方法,有效识别了遥感观测的锋面时空特征;同时基于有限体积海岸海洋模型(Finite-Volume Community Ocean Model,FVCOM)建立了适用于渤海的水动力模型,将FVCOM流场数据与海表SSC相结合,研究了黄河口切变锋对悬浮体通量的影响与河口泥沙输运路径。结果表明,切变锋从黄河口往东南方向移动,历时2~3 h,消失于10 m等深线附近,内涨外落(Inner-Flood-Outer-Ebb,IFOE)型切变锋的长度较内落外涨(Inner-Ebb-Outer-Flood,IEOF)型更长,IFOE型切变锋的平均长度约为22.4 km,最长能达到41 km以上,而IEOF型切变锋平均长度约为16.9 km;IFOE型切变锋消失的位置较IEOF型偏南。切变锋带由于具有低流速特征,能显著减小悬浮体通量,使大部分泥沙沉积在河口。切变锋处悬浮体通量不足其内侧的50%,超过50%的悬浮泥沙被切变锋阻隔在锋面内侧。切变锋使悬浮体通量提前减小,在6 m以浅海域即开始锐减。在潮流和锋面的影响下,非汛期黄河口泥沙主要往南或东南向莱州湾中部输运,再往东北输向莱州湾外,极少部分往西北和渤海中部输运。

The ocean fronts play an important role in the transport of matter in the offshore area in terms of dynamics.However,there are still some limitations in the high-resolution and large-scale observation and understanding of the fronts,especially in the estuary tidal fronts and its material transport process.Taking the shear front off the Yellow River Estuary as the study object,a high-precision inversion formula of sea surface suspended sediment concentration(SSC)in the Bohai Sea was established based on GOCI remote sensing data and water and sediment observation data,and the temporal and spatial characteristics of shear front were effectively identified by remote sensing observations,combining the principal of maximum cross correlation method with SSC gradient.At the same time,a hydrodynamic model suitable for the Bohai Sea was established based on FVCOM model,and the influence of shear front on sediment flux and sediment transport pathways in the Yellow River Estuary was studied combining FVCOM current data with sea surface SSC data.The results show that the shear fronts move from the Yellow River Estuary to the southeast lasting for 2~3 hours and disappear near the 10 m isobath.The inner-flood-outer-ebb(IFOE)shear front is longer than the inner-ebb-outer-flood(IEOF)shear front.The average length of the IFOE shear front is about 22.4 km,and the longest is more than 41 km,while the average length of the IEOF shear front is about 16.9 km.The IFOE shear front disappears southerly than IEOF shear front.Furthermore,the shear fronts can significantly reduce the sediment flux due to its low velocity characteristics,which makes most of the sediment deposited in the estuary.The sediment flux at the shear front zone is less than 50%of its inner side,and more than 50%of the suspended sediment is blocked by the shear fronts.And the shear fronts make the sediment flux decrease in advance,with the sediment flux sharply decreasing inside the 6m isobath resulting from shear fronts.On the condition of low discharge of water and sediment,the suspended sediment is mainly transported southerly or southeast into the middle Laizhou Bay effected by tidal current and shear front,and then transported northeast to the outside of Laizhou Bay.Little of it is transported northwest or to the middle Bohai Sea.