The Optical Characteristics Of The Three Elements In High Turbidity Water Of The Yangtze River Estuary And Its Influence On The Inversion Of TSM

The optical properties of the three elements of Case Ⅱ water color is crucial to establish the remote sensing inversion algorithm in the Yangtze Estuary waters due to the high suspended sediment concentration. The optical properties of the water body in estuarine waters is unique because of the interaction between the land and the sea. Based on field spectrum measurement and synchronous hydrological data, the optical characteristic of active substance in the Yangtze Estuary was analyzed during different tidal cycle in flood and dry seasons in 2014. The results show:total suspended solids concentration is the dominant factor on spectral reflectance in the Yangtze Estuary. The spatial distribution of suspended sediment concentration and the mean variation in dry season are higher than the flood season. The chlorophyll concentration is very low in this region whether in flood or dry seasons, and its impact on reflectance is very limited. The absorption coefficient is difficult to be detected by existing experimental methods. Due to the high turbidity of the water, the impact of chlorophyll on the spectral reflectance could be negligible. The CDOM concentration and absorption were all measured in the lab; the absorption of CDOM has larger temporal and spatial variation.The total suspended particles (TSM) concentration can reach 0.5kg/m3 or more during the spring tide, while at neap tide maximum TSM concentration only 1/3 of the spring tide. A lot of experience inversion algorithm cannot achieve good results since the high TSM concentration and the great variation within a tidal cycle in the Yangtze Estuary.According to the Landsat 8 bands set,38 set of in-situ optical and synchronous hydrology data were used to analyze the variation of total suspended maters concentration in the Yangtze Estuary under different tidal conditions. Five models were compared by the in-situ datum; the 3S model shown the best results. The simulated accuracy could reach to 0.899,0.972,0.589 and 0.682 for fortnightly tide, spring tide, neap tide and the outside site, respectively. The impact of CDOM and chlorophyll can be stripped in the lower concentration of total suspended particles region. Eight Landsat8 remote sensing images span a year is used to invers concentration of total suspended matters of the Yangtze Estuary, which may employed to describe the temple and spatial change of the suspended sediment during a year. This also verified that the model and the Landsat 8 could be adapted to monitor the suspended sediment in such large estuary and adjacent waters.