基于遥感和拟序结构的珠江河口悬沙锋时空变化特征及其动力机制研究

悬沙锋是水体悬沙浓度变化最显著区域，不仅揭示了清浑水界面，更对河口不同生物和水环境分布格局具有潜在指示意义。然而以往对珠江河口锋面研究多集中在河流淡水羽状锋，却极少关注悬沙锋。鉴于此，本项目首先利用多源卫星遥感资料反演珠江河口悬沙浓度，揭示珠江河口悬沙锋时空分布特征；其次结合水动力模型，引入时变动力系统拉格朗日拟序结构（LCS）和基于欧拉拟序结构的短时吸引轮廓（TRAPs）方法识别河口流场输运结构及其变化信息；最后通过建立不同拟序结构与悬沙锋之间的关联特征，诊断不同时空尺度下悬沙锋演变演变机制及其关键影响因子。项目采用TRAPs方法提取流场瞬时输运结构，可以获得卫星遥感难以得到的悬沙锋高频细致变化特征。项目研究成果不仅为珠江河口悬沙锋提供一种新认识，亦可为粤港澳大湾区突发水环境事件的应急处理提供可靠的科学指导。

A suspended sediment front (SSF) is a narrow boundary separating two water masses with marked differences in suspended sediment concentration. It serves as an important indicator for distributions of water masses with different marine life and environment. However, previous studies about fronts in the Pearl River Estuary (PRE) mainly focused on the plume front, while few pays attention to the SSF. Therefore, this study first reveal the spatio-temporal variation of the SSF in the PRE based on multi-source satellite data. Secondly, two coherent structures-Lagrangian Coherent Structures (LCS) and Transient Attracting Profiles (TRAPs)-are used to extract the horizontal transport structures in the PRE. Finally, based on the associated feature between coherent structures and suspended sediment fronts under different time scales, the dynamic mechanisms of the SSF in the PRE are discussed. The TRAPs used in this study can extract the instantaneous transport structure of a single velocity-field snapshot, and provide detailed and high-frequency information of the SSF variation, which is hard to obtain through remote sensing. The results of this study not only provide a new insight into the SSF in the PRE, but also reliable scientific guidances for the water hazard responses in the Guangdong-Hong Kong-Macao Greater Bay Area.