Research On Remote Sensing Retrieval And Dynamic Analysis Of Suspended Sediment In Zhoushan Sea Area

Zhoushan is located in the south of the Yangtze River estuary,the eastern part of Hangzhou Bay.The Yangtze River water flow south and Hangzhou Bay water to the east must pass through this land.So the water suspension sediment concentration is higher.The change of suspended sediment concentration in the water body will affect the water quality and reduce the primary productivity of the estuary,thus affecting the fishery and economic development of the estuary and adjacent waters and the normal operation of the ecosystem.On the other hand,it will also influence the waterway construction and construction Dam and other human activities.Therefore,it is very important to monitor the dynamic change of sediment concentration in Zhoushan sea area.In order to explore this change,this paper uses the geostationary ocean color Imager data with high time resolution per hour to realize atmospheric correction of image data through MODTRAN atmospheric radiation transmission model.Based on the measured data,a suspension sediment concentration inversion model based on single band,band ratio and multi-band combination was established and applied to GOCI data to invert the suspended sediment concentration in Zhoushan sea area.Finally,the trend of sediment concentration was analyzed according to the local tide level data.Several conclusions are drawn as follows:1.In the study area,the reflectance curves of different concentrations of suspended sediment have double peaks.The first main peak appears at about 570 nm and the second main peak is located at 810 nm.At 400 nm ~ 500 nm,the reflectance is relatively low and shows a gradual increase in reflectance,which is due to the high concentration of suspended sediment caused by the reflection;At 650 nm and 700 nm,no obvious absorption peaks and reflection peaks were observed.The chlorophyll a concentration was lower and the absorption and reflection effects were not obvious.Therefore,the sediment concentration in the study area was high.2.Using MODTRAN and the quasi-synchronous data to calibrate the atmosphere of GOCI image,the results show that the calibration result of this method is closer to the measured spectral curve.Therefore,the real remote sensing reflectance data can be obtained from the images to monitor the diurnal variation of suspended sediment concentration.3.According to the setting and measured data of GOCI L1 B band,a corresponding inversion model of suspended sediment concentration is constructed.The quadratic model with B7 /(B4 + B5)as the optimal model has a root mean square error of 0.0552 g / L,The average relative error is 17.05%.4.The spatial and temporal distribution of sediment in the study area is as follows: In spatial distribution,seawater in the study area is influenced by the islands during the course of travel,and the flow velocity changes.Part of sediment deposition in the west of the island,resulting in the west of the sediment concentration is generally higher than the east.Sediment content is the highest around the islands,the sediment concentration is generally about 0.45 g / L,while the open water volume fluctuates at 0.1g / L;On the time distribution,within one day,the concentration of suspended sediment has obvious changes.With the decrease of water level,the concentration of sediment increases.With the rise of water level,the concentration of sediment decreases.This is mainly due to the influx of outer seawater during the ups and downs,and the outflow of water bodies within the bay,resulting in the translational effect of sediment.