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Kabir M.A.,The Bureau of Meteorology | Kabir M.A.,Monash University | Dutta D.,CSIRO | Dutta D.,Monash University | Hironaka S.,NEWJEC Inc.
Water Resources Management | Year: 2014

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant's principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels. © 2014 Springer Science+Business Media Dordrecht.


Kabir M.A.,The Bureau of Meteorology | Dutta D.,CSIRO | Hironaka S.,NEWJEC Inc.
Water Resources Management | Year: 2014

Most process-based sediment dynamic models are based on the concept of sediment transport capacity (TC) of flow. Relationships between sediment TC and its characterized variables are found to vary widely, depending on the characteristics of a watershed and the underlying hydrological processes. This study has aimed to incorporate various widely used sediment transport capacity equations (TCEs) in a process-based sediment dynamic model, and to evaluate their relative performances in estimating suspended sediment dynamics at a river basin scale. The paper describes the modelling approaches and their application to a case study area (Abukuma River Basin, Japan), and then elaborates various parameters used in different TCEs with their useful impacts on modelling outcomes. The results of the case study have demonstrated that some of the TCEs are not suitable for simulating basin scale sediment dynamics. The TCEs that consist of more hydraulic parameters representing the flow and sediment transport processes have produced better outcomes. © 2014, Springer Science+Business Media Dordrecht.


Kabir M.A.,The Bureau of Meteorology | Dutta D.,CSIRO | Hironaka S.,NEWJEC Inc.
Water Resources Management | Year: 2014

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant’s principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels. © Springer Science+Business Media Dordrecht 2014.


Ying K.,CAS Institute of Atmospheric Physics | Zheng X.,CAS Institute of Atmospheric Physics | Zhao T.,CAS Institute of Atmospheric Physics | Frederiksen C.S.,The Bureau of Meteorology | And 2 more authors.
Climate Dynamics | Year: 2016

The patterns of interannual variability that arise from the slow (potentially predictable) and fast or intraseasonal (unpredictable) components of seasonal mean precipitation over eastern China are examined, based on observations from a network of 106 stations for the period 1951–2004. The analysis is done by using a variance decomposition method that allows identification of the sources of the predictability and the prediction uncertainty, from March–April–May (MAM) to September–October–November (SON). The average potential predictability (ratio of slow-to-total variance) of eastern China precipitation is generally moderate, with the highest value of 0.18 in June–July–August (JJA) and lowest value of 0.12 in April–May–June (AMJ). The leading predictable precipitation mode is significantly related to one-season-lead SST anomalies in the area of the Kuroshio Current during AMJ-to-JJA, the Indian-western Pacific SST in July–August–September (JAS), and the eastern tropical Pacific SST in MAM and SON. The prolonged linear trends, which are seen in the principal component time series associated with the second or third predictable precipitation modes in MJJ-to-ASO, also serve as a source of predictability for seasonal precipitation over eastern China. The predictive characteristics of the atmospheric circulation–precipitation relationship indicate that the western Pacific subtropical high plays a key role in eastern China precipitation. In addition, teleconnection patterns that are significantly related to the predictable precipitation component are also identified. The leading/second unpredictable precipitation modes from MAM to SON all show a monopole/dipole structure, which are accompanied by wavy circulation patterns that are related to intraseasonal events. © 2016 Springer-Verlag Berlin Heidelberg


Ying K.,CAS Institute of Atmospheric Physics | Zhao T.,CAS Institute of Atmospheric Physics | Zheng X.,CAS Institute of Atmospheric Physics | Quan X.-W.,University of Colorado at Boulder | And 2 more authors.
Climate Dynamics | Year: 2016

The Community Land Model version 3.5 is driven by an observation-based meteorological dataset to simulate soil moisture over China for the period 1951–2008. A method for identifying the patterns of interannual variability that arise from slow (potentially predictable) and intraseasonal (unpredictable) variability is also applied; this allows identification of the sources of the predictability of seasonal soil moisture in China, during March–April–May (MAM), June–July–August (JJA), September–October–November (SON) and December–January–February (DJF). The potential predictability (slow-to-total) of the soil moisture above 1 m is high, with lowest value of 0.76 in JJA and highest value of 0.94 in DJF. The spatial distribution of the potential predictability comprises a northwest–southeast gradient, with a minimum center over East China and a maximum center over the northwest. The most important source of predictability is from the soil moisture persistence, which generally accounts for more than 50 % of the variability in soil moisture. The SSTs in the Indian Ocean, the North Atlantic and the eastern tropical Pacific Oceans are also identified as important sources of variability in the soil moisture, during MAM, JJA and SON/DJF, respectively. In addition, prolonged linear trends in each season are an important source. Using the slow principal component time series as predictands, a statistical scheme for the seasonal forecasting of soil moisture across China is developed. The prediction skills, in terms of the percentage of explained variance for the verification period (1992–2008), are 59, 51, 62 and 77 % during MAM–DJF, respectively. This is considerably higher than a normal grid prediction scheme. © 2016 Springer-Verlag Berlin Heidelberg

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