scholarly journals Dynamically Constrained Interpolation of the Sparsely Observed Suspended Sediment Concentrations in Both Space and Time: A Case Study in the Bohai Sea

2018 ◽  
Vol 35 (5) ◽  
pp. 1151-1167 ◽  
Author(s):  
Xinyan Mao ◽  
Daosheng Wang ◽  
Jicai Zhang ◽  
Changwei Bian ◽  
Xianqing Lv
Keyword(s):  
Suspended Sediment ◽  
Bohai Sea ◽  
Transport Model ◽  
Suspended Sediment Transport ◽  
Model Parameters ◽  
Constrained Interpolation ◽  
The Bohai Sea ◽  
Space And Time ◽  
Twin Model ◽  
Suspended Sediment Concentrations

AbstractThe observed suspended sediment concentrations (SSCs) obtained from the water sampling are usually sparsely distributed in both space and time, which are traditionally applied just to calibrate other types of observations. In this study a dynamically constrained interpolation methodology (DCIM) is developed to interpolate these sparsely observed SSCs in the Bohai Sea. In this method the suspended sediment transport model is taken as dynamical constraints to interpolate the observations. Meanwhile, the interpolated results are optimized iteratively by adjusting the key model parameters using the adjoint method.The DCIM is first verified using the synthetic observations produced by twin model runs. The modeling results reveal that this method is effective at interpolating the sparsely observed artificial SSCs, even when the observations are heavily contaminated by data noise. Then, the sparsely observed practical SSCs obtained from a large area survey in the Bohai Sea are interpolated using the DCIM. The interpolated results are verified by randomly selected independent observations. The discrepancies between the interpolated SSCs and the observations are significantly decreased. When all the observations are interpolated, the final interpolated SSCs captured a majority (96.88%) of observations with a factor of 2 and the correlation coefficient between the observed and interpolated SSCs is 0.98. Besides, the interpolated results have presented the reasonable dynamical variations of SSCs in the space and time domains. The modeling results indicate that the DCIM is an effective tool for interpolating the sparsely observed SSCs in both space and time.

scholarly journals Estimation of Suspended Sediment Concentrations with Adcp in Danube River

2013 ◽  
Vol 61 (3) ◽  
pp. 232-240 ◽  
Author(s):  
Sándor Baranya ◽  
János Józsa
Keyword(s):  
Measurement Uncertainty ◽  
Suspended Sediment ◽  
Sediment Load ◽  
Empirical Relationship ◽  
Danube River ◽  
Suspended Sediment Transport ◽  
Model Parameters ◽  
Load Estimation ◽  
Suspended Sediment Concentrations ◽  
Sediment Load Estimation

Abstract An estimation procedure for suspended sediment concentrations based on the intensity of backscattered sound of acoustic Doppler current profilers (ADCP) is introduced in this paper. Based on detailed moving and fixed boat ADCP measurements with concurrent sediment sampling, we have successfully calibrated the estimation method for a reach of River Danube in Hungary, characterized by significant suspended sediment transport. The effect of measurement uncertainty and various data filtering on sediment load determination is also analyzed and quantified. Some of the physical model parameters describing the propagation of sound in water are estimated based on known empirical formulas, while other parameters are derived from measured. Regression analysis is used to obtain a relationship between the intensity of backscattered sound and sediment concentrations. The empirical relationship has been then used to estimate the suspended sediment concentrations from the ADCP data collected in fixed and moving boat measurement operation mode, along verticals and path-lines, respectively. We show that while some measurement uncertainty is inherent to the acoustic Doppler principle, it is further enhanced by the complexity of the near-bottom sediment-laden flow. This uncertainty has then a significant effect on the local sediment load estimation. In turn, reasonable smoothing of raw velocity and backscatter intensity data shows insignificant impact on cross-sectional sediment load estimation.

scholarly journals Application of Dynamically Constrained Interpolation Methodology in Simulating National-Scale Spatial Distribution of PM2.5 Concentrations in China

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 272
Author(s):  
Ning Li ◽  
Junli Xu ◽  
Xianqing Lv
Keyword(s):  
Transport Model ◽  
Ground Level ◽  
Kriging Interpolation ◽  
Model Parameters ◽  
National Scale ◽  
Constrained Interpolation ◽  
Simulation Accuracy ◽  
Interpolation Accuracy ◽  
Geographical Regions ◽  
The Right

Numerous studies have revealed that the sparse spatiotemporal distributions of ground-level PM2.5 measurements affect the accuracy of PM2.5 simulation, especially in large geographical regions. However, the high precision and stability of ground-level PM2.5 measurements make their role irreplaceable in PM2.5 simulations. This article applies a dynamically constrained interpolation methodology (DCIM) to evaluate sparse PM2.5 measurements captured at scattered monitoring sites for national-scale PM2.5 simulations and spatial distributions. The DCIM takes a PM2.5 transport model as a dynamic constraint and provides the characteristics of the spatiotemporal variations of key model parameters using the adjoint method to improve the accuracy of PM2.5 simulations. From the perspective of interpolation accuracy and effect, kriging interpolation and orthogonal polynomial fitting using Chebyshev basis functions (COPF), which have been proved to have high PM2.5 simulation accuracy, were adopted to make a comparative assessment of DCIM performance and accuracy. Results of the cross validation confirm the feasibility of the DCIM. A comparison between the final interpolated values and observations show that the DCIM is better for national-scale simulations than kriging or COPF. Furthermore, the DCIM presents smoother spatially interpolated distributions of the PM2.5 simulations with smaller simulation errors than the other two methods. Admittedly, the sparse PM2.5 measurements in a highly polluted region have a certain degree of influence on the interpolated distribution accuracy and rationality. To some extent, adding the right amount of observations can improve the effectiveness of the DCIM around existing monitoring sites. Compared with the kriging interpolation and COPF, the results show that the DCIM used in this study would be more helpful for providing reasonable information for monitoring PM2.5 pollution in China.

scholarly journals Experimental validation of a cohesive suspended sediment transport model for two Mexican rivers

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Juan Antonio García-Aragón ◽  
Klever Izquierdo-Ayala ◽  
María Mercedes Castillo-Uzcanga ◽  
Laura Carrillo-Bibriezca ◽  
Humberto Salinas-Tapia
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Experimental Validation ◽  
Transport Model ◽  
Suspended Sediment Transport ◽  
Sediment Transport Model

Study on the Coastal Suspended Sediment Transport Based on Multi-Source Satellite Remote Sensing Imagery

2013 ◽  
Vol 718-720 ◽  
pp. 371-376
Author(s):  
Yin Cai ◽  
Meng Guo Li ◽  
Ming Xiao Xie
Keyword(s):  
Remote Sensing ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Coastal Area ◽  
Satellite Remote Sensing ◽  
Wind Waves ◽  
Suspended Sediment Transport ◽  
Nearshore Zone ◽  
Retrieval Technique ◽  
Suspended Sediment Concentrations

Based on a series of multi-source satellite remote sensing imageries and wind parameters extracted from QuickSCAT satellite datasets, the surface suspended sediment concentrations (SSC) of the Zhuanghe coastal area, China was investigated using the retrieval technique. The results showed that the SSC of the Zhuanghe coastal area is higher in the nearshore zone, and gradually diminishes to the offshore. During the ebbing process, the range of high SSC zone is wider than that during the flooding process. This feature indicated that the suspended sediment transport is mainly determined by the ebb currents, and the sediment source comes from the nearshore shallow flats, where the sediments could be entrained by the wind waves and then diffuses offshore or alongshore with the tidal currents.

Data assimilation in a coupled physical-biological model for the Bohai Sea and the Northern Yellow Sea

2008 ◽  
Vol 59 (6) ◽  
pp. 529 ◽  
Author(s):  
Qing Xu ◽  
Hui Lin ◽  
Yuguang Liu ◽  
Xianqing Lv ◽  
Yongcun Cheng
Keyword(s):  
Chlorophyll A ◽  
Annual Cycle ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Biological Model ◽  
Model Parameters ◽  
The Bohai Sea ◽  
Northern Yellow Sea ◽  
Ocean Models ◽  
Adjoint Assimilation

One difficulty with coupled physical-biological ocean models is determining optimal values of poorly known model parameters. The variational adjoint assimilation method is a powerful tool for the automatic estimation of parameters. We used this method to incorporate remote-sensed chlorophyll-a data into a coupled physical-biological model developed for the Bohai Sea and the Northern Yellow Sea. A 3-D NPZD model of nutrients (N), phytoplankton (P), zooplankton (Z) and detritus (D) was coupled with a physical model, the Princeton Ocean Model. Sensitivity analysis was carried out to choose suitable control variables from the model parameters. Numerical twin experiments were then conducted to demonstrate whether the spatio-temporal resolutions of the observations were adequate for estimating values of the control variables. Finally, based on the success of the twin experiments, we included remote-sensed chlorophyll-a data in the NPZD model. With the adjoint assimilation of these chlorophyll-a data, the coupled model better describes spring and autumn phytoplankton blooms and the annual cycle of phytoplankton at the surface layer for the study area. The annual cycle of simulated surface nutrient concentrations also agreed well with field observations. The adjoint method greatly improves the modelling capability of coupled ocean models, helping us to better understand and model marine ecosystems.

scholarly journals Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

2014 ◽  
Vol 18 (8) ◽  
pp. 3033-3053 ◽  
Author(s):  
N. V. Manh ◽  
N. V. Dung ◽  
N. N. Hung ◽  
B. Merz ◽  
H. Apel
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Large Scale ◽  
Transport Model ◽  
Mekong Delta ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Mineral Fertilizers ◽  
Suspended Sediment Transport ◽  
Extreme Flood

Abstract. Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for estimating the benefits of annual Mekong floods for agriculture and fishery, and is an important piece of information with regard to the assessment of the impacts of deltaic subsidence and climate-change-related sea level rise on delta morphology.

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