| Estuaries and coasts, important areas for forefront of reforming and opening and marine exploitation, are playing an important role on the development of social economics, which are the valuable resources for civil essential living. However, with the rapid development of the population, industrialization and urbanization in recent decades, the increasing of discharge of industrial wastewater and sewage and watershed exploiting worsen the water environment and severely destroy eco-system. The suspended sediment is an important component in coastal water. It is significantly important for researches on coastal water quality, relief and environment, water engineering and dock harbor construction, and sustainably utilizing coastal resources to fast and accurately acquire quantitative information for suspended sediment concentration and its spatio-temporal pattern.Remote sensing as a tool for quick synoptic data acquisition, synchronously and periodically records rich information for examining and studying various surface phenomena of the continuous spatial distribution on the earth. Remote sensing technology is widely used, but it is still a key problem to quantitatively retrieve suspended sediment concentration in coastal complex waters, because of disturbance of remote sensing signals from complex water, remote sensing mechanism of suspended sediment model, and the inconsistency between remote sensing and in situ measurement. What’s more, remote sensing image records periodical and point-in-time state, and optical sensors are constrained in bad weather condition. In the event of water quality disaster, remote sensing may be invalid to accurately reflect the mechanism of the disaster. The dynamics of water quality deterioration can not be captured by periodically revisit of satellite.The process of hydrodynamics plays a vital role on the study of marine environment, which can describe the continuous dynamics in a period of time. It is possible to reveal the occurrence and development mechanism of water quality problem by understanding the process of hydrodynamics to resolve ecological problems. It is difficult to acquire initial suspended sediment concentration in the sea surface for numerical simulation, which is expensive and labor cost. Traditional numerical simulation is driven by limited points of field observation data as initial condition for sediment transport model.This study aimed to explore coupling remote sensing retrieval and hydrodynamic-sediment numerical simulation which is fully taken into account of the advantage of remote sensing for quickly acquiring data and numerical simulation for physical process modelling. In this dissertation, taking the Bohai Sea as an example, remote sensing retrieval models are established using in situ spectral and suspended sediment concentration after summarizing current study and development trend of remote sensing retrieval and numerical simulation. The retrieval models are applied to ENVISAT/MERIS and EOS/MODIS to retrieve suspended sediment distribution in the Bohai Sea. The approach of coupling remote sensing and numerical simulation is implemented to monitor sediment transport, and analyze bottom sediment resuspension as well. The spatio-temporal discipline of sediment dynamics are also studied by numerical simulated results, remote sensed sediment map and in situ measurement data, then the spatio-temporal inconsistency of suspended sediment concentrate from multi-source are assessed. The major works accomplished and achievements of this study are as follows:(1) Suspended sediment remote sensing retrieval in the Bohai Sea. A retrieval model is proposed for MODIS Band-1 with the root mean square error (RMSE) of 0.786mg/L, the mean relative error (MRE) 6.9%, and the correlation coefficient R20.715, which are acceptable. The suspended sediment concentration is retrieved based on MERIS and MODIS images in the Bohai Sea, which is verified by the in situ measurement data. The good results of suspended sediment concentration retrieved have laid a solid foundation for the study of sediment transport by coupling remote sensing and numerical simulation.(2) Study on suspended sediment numerical simulation coupling remote sensing retrieval. Taking the suspended sediment concentration in the Bohai Sea as an example, the current, tide level and suspended sediment concentration is simulated using remote sensed sediment map to initialize sediment transport model. The model parameters of sediment transport are calibrated by retrieved sediment map, and a group of hydrodynamic and sediment model parameters are obtained, which is suit for numerical simulation in the Bohai Sea. The simulated suspended sediment concentration and tide levels are verified by in situ data. The final simulated results and retrieved results can be cross-validated and compared. The results show that coupling remote sensing retrieval and numerical simulation is superior to monitor water environment three-dimensionally in coastal water, which has complementary for both technologies.(3) Study the transport and bottom resuspension of sediment coupling remote sensing and numerical simulation. There is a good correlative between MODIS Band-1 reflectance atmospherically corrected and numerically simulated suspended sediment concentration, which validates the feasible that remote sensing reflectance can be indicate suspended sediment concentration directly. So the correlation can be used to study the bottom resuspension effect on surface suspended sediment concentration. The change tendency of suspended sediment concentration in the bottom layer is similar with the surface sediment through examining the synoptic wind effect on sediment bottom resuspension. The contribution of bottom sediment resuspension on surface suspended sediment concentration is investigated using MODIS Aqua Band-1 reflectance. The result shows that the surface suspended sediments are from the bottom sediment resuspension and its transport in most areas of the Bohai Sea, including north of Bohai Bay, southeast of Laizhou Bay, vicinity of Qinhuangdao, east of Liaodong Bay and Bohai strait, while in the estuary and areas away 20-30km of Yellow River, the surface sediment mainly comes from Yellow River.(4) Suspended sediment concentration spatio-temporal assess coupling remote sensing and numerical simulation. Different time scale of suspended sediment concentration is analyzed in hours and monthly to examine the temporal discipline.In addition, in order to examine the sediment concentration differences from different point of interested, the time series of concentration at different site are selected. The result shows the amplitude of variation in high sediment concentration water is larger then that in related clear water. The spatial distribution patterns are similar in different layers. The suspended sediment concentration is generally increasing with the depth increasing, and variation amplitudes vary in different site. From time series of sediment concentration in different layers, the suspended sediment concentrations vary with time lapse. The change tendency of concentration is consistent in most times, but there is inconsistency between upper layers and lower layers sometimes, especially frequently in the estuary.Finally, the spatio-temporal inconsistencies of suspended sediment concentration from remote sensing, numerical simulation and in situ measurement are investigated. The differences from in situ measurement data and remote sensing retrieved sediment concentration in temporal further validate that it is essential to establish relationship between remote sensed reflectance and numerical simulated sediment concentration. The simulated ability of ocean model is examined by analyzing the significant different sediment concentration areas. The possible reasons for the inconsistency of retrieved suspended sediment concentration and numerically simulated results are discussed subsequently. |
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