Hydrological Modelling and Climate Change Impact Assessment on Future Floods in the Norwegian Arctic Catchments

Climate change is expected to alter the hydrological cycle in the Arctic, which would result in the increase in intensity and frequency of hydrological extreme events such as flooding. Noticeably, the changes in flooding due to climate change would severely affect human life, infrastructures, the environment, ecosystem, and socio-economic development in the impacted areas. Hydrological models are state-of-the-art tools for assessing the impact of climate change on hydrological processes. However, performing hydrological simulation/projection in the Arctic is challenging because of the complex hydrological processes and data-sparse features in the region. In consideration of those issues, this PhD research aims: (1) to assess the performances of hydrological models in the Arctic, (2) to investigate the alternative weather inputs for running the hydrological models in the Arctic region with scattered monitoring data, (3) to evaluate the effects of the models’ structure and parameterization and the spatial resolution of weather inputs on the results of hydrological simulations, and (4) to project future hydrological events under climate change impacts using the current hydrological model, and analyse the reliability/uncertainty of the projection. To fulfil the research’s objectives, several methodologies were applied. Firstly, a comprehensive review was conducted to address the current capacities and challenges of twelve well-known hydrological models, including surface hydrological models and subsurface hydrological models/groundwater models/cryo-hydrogeological models. These models have previously been applied or have the potential for application in the Arctic. Next, the physically based, semi-distributed model, SWAT (soil and water assessment tool), was selected as a suitable model, among other potential models, to assess its performance for hydrological simulations and to verify the potential application of reanalysis weather data. Moreover, the SWAT was coupled with multiple ensemble global and regional climate models’ simulations to project the future hydrological impacts under climate change (in 2041-2070). The study areas were mainly focused in the Norwegian Arctic catchments

Quantifying the effects of watershed subdivision scale and spatial density of weather inputs on hydrological simulations in a Norwegian Arctic watershed

The effects of watershed subdivisions on hydrological simulations have not been evaluated in Arctic conditions yet. This study applied the Soil and Water Assessment Tool and the threshold drainage area (TDA) technique to evaluate the impacts of watershed subdivision on hydrological simulations at a 5,913-km2 Arctic watershed, Målselv. The watershed was discretized according to four TDA scheme scales including 200, 2,000, 5,000, and 10,000 ha. The impacts of different TDA schemes on hydrological simulations in water balance components, snowmelt runoff, and streamflow were investigated. The study revealed that the complexity of terrain and topographic attributes altered significantly in the coarse discretizations: (1) total stream length (−47.2 to −74.6%); (2) average stream slope (−68 to −83%); and (3) drainage density (−24.2 to −51.5%). The spatial density of weather grid integration reduced from −5 to −33.33% in the coarse schemes. The annual mean potential evapotranspiration, evapotranspiration, and lateral flow slightly decreased, while areal rainfall, surface runoff, and water yield slightly increased with the increases of TDAs. It was concluded that the fine TDAs produced finer and higher ranges of snowmelt runoff volume across the watershed. All TDAs had similar capacities to replicate the observed tendency of monthly mean streamflow hydrograph, except overestimated/underestimated peak flows. Spatial variation of streamflow was well analyzed in the fine schemes with high density of stream networks, while the coarse schemes simplified this. Watershed subdivisions affected model performances, in the way of decreasing the accuracy of monthly streamflow simulation, at 60% of investigated hydro-gauging stations (3/5 stations) and in the upstream. Furthermore, watershed subdivisions strongly affected the calibration process regarding the changes in sensitivity ranking of 18 calibrated model parameters and time it took to calibrate

A Review of Hydrological Models Applied in the Permafrost-Dominated Arctic Region

The Arctic region is the most sensitive region to climate change. Hydrological models are fundamental tools for climate change impact assessment. However, due to the extreme weather conditions, specific hydrological process, and data acquisition challenges in the Arctic, it is crucial to select suitable hydrological model(s) for this region. In this paper, a comprehensive review and comparison of different models is conducted based on recently available studies. The functionality, limitations, and suitability of the potential hydrological models for the Arctic hydrological process are analyzed, including: (1) The surface hydrological models Topoflow, DMHS (deterministic modeling hydrological system), HBV (Hydrologiska Byråns Vattenbalansavdelning), SWAT (soil and water assessment tool), WaSiM (water balance simulation model), ECOMAG (ecological model for applied geophysics), and CRHM (cold regions hydrological model); and (2) the cryo-hydrogeological models ATS (arctic terrestrial simulator), CryoGrid 3, GEOtop, SUTRA-ICE (ice variant of the existing saturated/unsaturated transport model), and PFLOTRAN-ICE (ice variant of the existing massively parallel subsurface flow and reactive transport model). The review finds that Topoflow, HBV, SWAT, ECOMAG, and CRHM are suitable for studying surface hydrology rather than other processes in permafrost environments, whereas DMHS, WaSiM, and the cryo-hydrogeological models have higher capacities for subsurface hydrology, since they take into account the three phase changes of water in the near-surface soil. Of the cryo-hydrogeological models reviewed here, GEOtop, SUTRA-ICE, and PFLOTRAN-ICE are found to be suitable for small-scale catchments, whereas ATS and CryoGrid 3 are potentially suitable for large-scale catchments. Especially, ATS and GEOtop are the first tools that couple surface/subsurface permafrost thermal hydrology. If the accuracy of simulating the active layer dynamics is targeted, DMHS, ATS, GEOtop, and PFLOTRAN-ICE are potential tools compared to the other models. Further, data acquisition is a challenging task for cryo-hydrogeological models due to the complex boundary conditions when compared to the surface hydrological models HBV, SWAT, and CRHM, and the cryo-hydrogeological models are more difficult for non-expert users and more expensive to run compared to other models

SOME DEFINITIONS FOR CONVOLUTIONS AND THE CONVOLUTIONS FOR THE FOURIER TRANSFORMS WITH GEOMETRIC VARIABLES

Joint Research on Environmental Science and Technology for the Eart

Stability of Cracked Plates with Nonlinearly Variable Thickness Resting on Elastic Foundations

In this paper, the stability of rectangular cracked plates with nonlinearly variable thickness resting on the elastic foundations is studied. The thickness of the plate varies exponentially along the x-axis. Meanwhile, the elastic foundation is modeled by a two-parameter Pasternak elastic foundation type. The crack is assumed at the center of the plate with variable length and angle of inclination. The establishment of the stability equations of the cracked plate is based on the Higher Order Shear Deformation Theory (HSDT) combined with the phase field theory. Next, using the finite element method to solve the equations to find the minimum force that causes plate instability. To test the reliability of the computational theory, the results are compared with several reputable published papers. Then, the article will investigate the influence of elastic foundation, crack location, crack length and crack inclination on the stability of plate. The results show that the elastic foundation has a great influence on the plate stability, while the crack inclination angle has less influence. Finally, there are some images of the destabilization patterns of cracked plates placed on an elastic foundation

Convolution for the transform induced by Fourier integral transform and its inverse

Joint Research on Environmental Science and Technology for the Eart

Stability of Cracked Plates with Nonlinearly Variable Thickness Resting on Elastic Foundations

In this paper, the stability of rectangular cracked plates with nonlinearly variable thickness resting on the elastic foundations is studied. The thickness of the plate varies exponentially along the x-axis. Meanwhile, the elastic foundation is modeled by a two-parameter Pasternak elastic foundation type. The crack is assumed at the center of the plate with variable length and angle of inclination. The establishment of the stability equations of the cracked plate is based on the Higher Order Shear Deformation Theory (HSDT) combined with the phase field theory. Next, using the finite element method to solve the equations to find the minimum force that causes plate instability. To test the reliability of the computational theory, the results are compared with several reputable published papers. Then, the article will investigate the influence of elastic foundation, crack location, crack length and crack inclination on the stability of plate. The results show that the elastic foundation has a great influence on the plate stability, while the crack inclination angle has less influence. Finally, there are some images of the destabilization patterns of cracked plates placed on an elastic foundation

US-China rivalry in Southeast Asia region: a study on the South China Sea case

Southeast Asia is one of the places where fierce rivalry is taking place between the two leading powers in the world today - the US and China. The US-China rivalry in this region takes place in key fields, from politics - diplomacy, economy, security - defense to "soft power", the most prominent of which is the South China Sea issue. This article analyzes the strategic importance of the South China Sea in the policy of the US and China, the competition between the US and China in Southeast Asia in general, and the South China Sea in particular. To achieve this goal, the authors use research methods in international relations to analyze the main issues of the study. In addition to reviewing previous scholarly research and reviews, the authors use a comparative approach to assess the interactions between theory and data. The authors believe the data is important for accurately assessing the strategic competition between the US and China in Southeast Asia and the South China Sea. The rise of China in the early years of the XXI century strongly influenced the adjustment of the US policy in Southeast Asia and the powerful US-China rivalry in this region and the South China Sea. This rivalry is becoming increasingly complicated, and geopolitical conflicts between major powers are possible in the following years

Convolutions of the fourier-cosine and fourier-sine integral transforms and integral equations of the convolution type

This paper introduces general definitions of convolutions without and with weight, obtains four new convolutions and generalized convolutions of the Fourier-cosine and Fourier-sine integral transforms. Furthermore, the paper investigates into a class of integral equations with the mixed Toeplitz-Hankel kernel. Namely, by using the constructed convolutions the explicit solutions are obtained

THE INFRASTRUCTURE AND ENVIRONMENT IN THE OLD TENEMENTS IN HANOI

Joint Research on Environmental Science and Technology for the Eart