The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Zhen Liu - One of the best experts on this subject based on the ideXlab platform.
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using molecular dynamics to unravel phase composition behavior of nano size pores in Frozen Soils does young laplace equation apply in low temperature range
Canadian Geotechnical Journal, 2018Co-Authors: Chao Zhang, Zhen Liu, Peng DengAbstract:The phase composition curve of Frozen Soils is a fundamental relationship in understanding permafrost and seasonally Frozen Soils. However, due to the complex interplay between adsorption and capillarity, a clear physically based understanding of the phase composition curve in the low temperature range, i.e., <265 K, is still absent. Especially, it is unclear whether the Young–Laplace equation corresponding to capillarity still holds in nano-size pores where adsorption could dominate. In this paper, a framework based on molecular dynamics was developed to investigate the phase transition behavior of water confined in nano-size pores. A series of simulations was conducted to unravel the effects of the pore size and wettability on the freezing and melting of pore water. This is the first time that the phase composition behavior of Frozen Soils is analyzed using molecular dynamics. It is found that the Young–Laplace equation may not apply in the low temperature range.
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Predicting the phase composition curve in Frozen Soils using index properties: A physico-empirical approach
Cold Regions Science and Technology, 2014Co-Authors: Zhen Liu, Xiong YuAbstract:The relationship between unFrozen water content and temperature in Frozen Soils, which is referred to as the phase composition curve (PCC), is a fundamental relationship in cold regions engineering. In a previous study, the authors succeeded in developing a physical description and a physically-based equation for the PCC, which overcomes the limitations of the existing empirical approaches. Here, the authors propose a physico-empirical approach to predict the parameters in this equation to facilitate the calculation of the PCC in practice. An accurate prediction of the PCC will only need simple soil index properties and one measured data point for constraint. In this approach, the four parameters in the PCC equation are first calculated from soil index properties using accepted formulas. Two selected parameters are then adjusted by a curve fitting process using the measured data point. A criterion was suggested for obtaining the best point. This new approach was implemented using a computer program to automate the process. Validations with data from several Soils indicated that the approach offers consistent and accurate predictions of PCCs when used with Zapata's model for plastic Soils and with the Mechanistic-Empirical Pavement Design Guide (MEPDG) model for non-plastic Soils. This study thus bridges an important gap between the theory and application of PCCs.
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predicting the phase composition curve in Frozen Soils using index properties a physico empirical approach
Transportation Research Board 93rd Annual MeetingTransportation Research Board, 2014Co-Authors: Zhen LiuAbstract:The relationship between unFrozen water content and temperature in Frozen Soils, which is referred to as the Phase Composition Curve (PCC), is a fundamental relationship in cold regions engineering. In a previous study, the authors succeeded in developing a physical description and a physically-based equation for the PCC, which overcomes the limitations of the existing empirical approaches. This study proposes a physico-empirical approach to predict the parameters in this equation to facilitate the applications of the PCC. An accurate prediction of the PCC will only need simple soil index properties and one measured data point. In this method, the four parameters in the PCC equation are first calculated from soil index properties using accepted formulas. Two selected parameters are then adjusted by a curve fitting process using a measured data point. A criterion was suggested for obtaining the one point measurement. This new approach was implemented using a computer program to automate the process. Validations with measured results indicated that the approach offers consistent and accurate predictions of PCCs when used with Zapata's model for plastic Soils and with the Mechanistic-Empirical Pavement Design Guide (MEPDG) model for non-plastic Soils, respectively. This study thus bridges an important gap between the theory and applications of PCCs.
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physically based equation for phase composition curve of Frozen Soils
Transportation Research Record, 2013Co-Authors: Zhen LiuAbstract:The relationship between unFrozen water content (or saturation in freezing and thawing) and temperature, which is referred to as the phase composition curve in Frozen Soils, is a fundamental relationship in cold regions engineering. Because of the lack of a physical basis, there have been only empirical equations for this relationship. This study investigated the mechanisms underlying the phase composition curve. A detailed physical basis was established on the basis of the soil freezing characteristic curve, the Clapeyron equation, and the bundle of cylindrical capillary model. From this physical basis, a closed-form equation was developed for the formulation and prediction of this curve. This physically based equation quantifies the unique correlation between saturation and temperature in Frozen Soils and takes various factors into account, such as the soil saturation under unFrozen conditions and the lowest temperature used in experiments. The equation was validated with phase composition data measured...
J W Pomeroy - One of the best experts on this subject based on the ideXlab platform.
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an extension of the force restore method to estimating soil temperature at depth and evaluation for Frozen Soils under snow
Journal of Geophysical Research, 2002Co-Authors: Tomoyoshi Hirota, J W Pomeroy, R J Granger, Charles MauleAbstract:Hirota, T., Pomeroy, J. W., Granger, R. J., Maule, C. P. (2002). An extension of the force-restore method to estimating soil temperature at depth and evaluation for Frozen Soils under snow. Journal of Geophysical Research-Atmospheres, 107, Issue D4.
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estimating areal snowmelt infiltration into Frozen Soils
Hydrological Processes, 2001Co-Authors: D M Gray, Litong Zhao, B Toth, J W Pomeroy, R J GrangerAbstract:An algorithm for estimating areal snowmelt infiltration into Frozen Soils is developed. Frozen Soils are grouped into classes according to surface entry condition as: (a) Restricted-water entry is impeded by surface conditions, (b) Limited-capillary flow predominates and water entry is influenced primarily by soil physical properties, and (c) Unlimited-gravity flow predominates and most of the meltwater infiltrates. For Limited Soils cumulative infiltration over time is estimated by a parametric equation from surface saturation, initial soil moisture content (water + ice), initial soil temperature and infiltration opportunity time. Total infiltration into Unlimited and Limited Soils is constrained by the available water storage capacity. This constraint is also used to determine when Limited Soils have thawed. The minimum spatial scale of the infiltration model is established for Limited Soils by the variabilities in surface saturation, snow water equivalent, soil infiltrability, soil moisture (water + ice) and depth of soil freezing. Since snowmelt infiltration is influenced by other processes and factors that affect snow ablation, it is assumed that the infiltrability spatial scale should be consistent with the scales used to describe these variables. For open, northern, cold regions the following order in spatial scales is hypothesized: Frozen ground > snowmelt > snow water equivalent ≥ Frozen soil infiltrability > soil moisture (water + ice) and snow water. For mesoscale application of the infiltration model it is recommended that the infiltrability scale be taken equal to the scale used to describe the areal extent and distribution of the water equivalent of the snowcover that covers Frozen ground. Scaling the infiltrability of Frozen Soils in this manner allows one to exploit established landscape-stratification methodology used to derive snow accumulation means and distribution. Scaling of soil infiltrability at small scales (microscale) is complicated and requires information on the association(s) between the spatial distributions of soil moisture (water + ice) and snow water. A flow chart of the algorithm is presented.
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snow Frozen Soils and permafrost hydrology in canada 1995 1998
Hydrological Processes, 2000Co-Authors: Mingko Woo, Philip Marsh, J W PomeroyAbstract:This paper provides an overview of Canadian research on snow, Frozen Soils and permafrost hydrology during the years 1995-98. There were significant advances in the understanding of processes and the development of models of snow accumulation and melt, including the relocation of snow by wind, snow interception in forest canopies, sublimation and energy balance during snowmelt. A major aspect was the development of physically based predictive techniques that account for the effects of heterogeneous topography, vegetation and snow properties, and complex boundary-layer development on snow accumulation, evaporation, melt and runoff. Another advancement is in the linkage of physical snow processes with chemical models to better describe ion accumulation and elution from snow. Snow ecology has shown the interactions in nutrient cycles that involve snow. Frozen ground research has resulted in significantly improved models of Frozen soil infiltration, based on both field observations and thermodynamic principles. Research in permafrost regions includes the exfiltration of groundwater in the seasonally thawed zone and the occurrence of perennial springs discharged from below the permafrost. Groundwater discharge is important to features such as icings and the occurrence of wetlands in a polar desert. Processes governing runoff generation on hillslopes have been examined, both in continuous and discontinuous permafrost zones. In terms of future research directions, consideration should be given to continued intensive field studies of cold region hydrological processes and the incorporation of these processes into aquatic chemistry and hydrological models and land surface schemes used in atmospheric models. A better understanding of the role of hydrological boundaries in affecting the rates of processes is needed. The question of scaling processes up from the small scale at which they are relatively well understood, to the larger scales necessary to address global environmental concerns also should be addressed.
Philip Marsh - One of the best experts on this subject based on the ideXlab platform.
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snow Frozen Soils and permafrost hydrology in canada 1999 2002
Hydrological Processes, 2005Co-Authors: Mingko Woo, Philip MarshAbstract:An overview is provided of Canadian research on snow, Frozen Soils and permafrost hydrology for 1999-2002, the period between the 1999 IUGG meeting in Birmingham and the 2003 IUGG in Sapporo. Snow research during this period emphasized the blowing snow and sublimation processes, the role of trees in snow distribution, and melt and the effect of heat advection on snowmelt, from patch to regional scales. Regional-scale studies, largely in connection with the Mackenzie GEWEX study, examined the snow conditions of the lower Mackenzie basin and developed a coupled land surface scheme-hydrological model that incorporates snow processes. In frost hydrology, the effects of organic Soils on runoff generation and flow delivery were given much attention. Field investigations ranged from plot to hillslope scales, and the results indicate that organic layers of high porosity permit the production of quick flow, even when Frozen. Highly fractured bedrock in the Canadian Shield has likewise the effect of permitting snowmelt infiltration at below-freezing temperatures. Finally, changes in snow-covered areas and in snow equivalent over periods from a decade to a century were examined. The responses of snow and ground ice to the warm year of 1998 were also studied as an indication of hydrological responses to climatic warming.
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snow Frozen Soils and permafrost hydrology in canada 1995 1998
Hydrological Processes, 2000Co-Authors: Mingko Woo, Philip Marsh, J W PomeroyAbstract:This paper provides an overview of Canadian research on snow, Frozen Soils and permafrost hydrology during the years 1995-98. There were significant advances in the understanding of processes and the development of models of snow accumulation and melt, including the relocation of snow by wind, snow interception in forest canopies, sublimation and energy balance during snowmelt. A major aspect was the development of physically based predictive techniques that account for the effects of heterogeneous topography, vegetation and snow properties, and complex boundary-layer development on snow accumulation, evaporation, melt and runoff. Another advancement is in the linkage of physical snow processes with chemical models to better describe ion accumulation and elution from snow. Snow ecology has shown the interactions in nutrient cycles that involve snow. Frozen ground research has resulted in significantly improved models of Frozen soil infiltration, based on both field observations and thermodynamic principles. Research in permafrost regions includes the exfiltration of groundwater in the seasonally thawed zone and the occurrence of perennial springs discharged from below the permafrost. Groundwater discharge is important to features such as icings and the occurrence of wetlands in a polar desert. Processes governing runoff generation on hillslopes have been examined, both in continuous and discontinuous permafrost zones. In terms of future research directions, consideration should be given to continued intensive field studies of cold region hydrological processes and the incorporation of these processes into aquatic chemistry and hydrological models and land surface schemes used in atmospheric models. A better understanding of the role of hydrological boundaries in affecting the rates of processes is needed. The question of scaling processes up from the small scale at which they are relatively well understood, to the larger scales necessary to address global environmental concerns also should be addressed.
Mingko Woo - One of the best experts on this subject based on the ideXlab platform.
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snow Frozen Soils and permafrost hydrology in canada 1999 2002
Hydrological Processes, 2005Co-Authors: Mingko Woo, Philip MarshAbstract:An overview is provided of Canadian research on snow, Frozen Soils and permafrost hydrology for 1999-2002, the period between the 1999 IUGG meeting in Birmingham and the 2003 IUGG in Sapporo. Snow research during this period emphasized the blowing snow and sublimation processes, the role of trees in snow distribution, and melt and the effect of heat advection on snowmelt, from patch to regional scales. Regional-scale studies, largely in connection with the Mackenzie GEWEX study, examined the snow conditions of the lower Mackenzie basin and developed a coupled land surface scheme-hydrological model that incorporates snow processes. In frost hydrology, the effects of organic Soils on runoff generation and flow delivery were given much attention. Field investigations ranged from plot to hillslope scales, and the results indicate that organic layers of high porosity permit the production of quick flow, even when Frozen. Highly fractured bedrock in the Canadian Shield has likewise the effect of permitting snowmelt infiltration at below-freezing temperatures. Finally, changes in snow-covered areas and in snow equivalent over periods from a decade to a century were examined. The responses of snow and ground ice to the warm year of 1998 were also studied as an indication of hydrological responses to climatic warming.
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snow Frozen Soils and permafrost hydrology in canada 1995 1998
Hydrological Processes, 2000Co-Authors: Mingko Woo, Philip Marsh, J W PomeroyAbstract:This paper provides an overview of Canadian research on snow, Frozen Soils and permafrost hydrology during the years 1995-98. There were significant advances in the understanding of processes and the development of models of snow accumulation and melt, including the relocation of snow by wind, snow interception in forest canopies, sublimation and energy balance during snowmelt. A major aspect was the development of physically based predictive techniques that account for the effects of heterogeneous topography, vegetation and snow properties, and complex boundary-layer development on snow accumulation, evaporation, melt and runoff. Another advancement is in the linkage of physical snow processes with chemical models to better describe ion accumulation and elution from snow. Snow ecology has shown the interactions in nutrient cycles that involve snow. Frozen ground research has resulted in significantly improved models of Frozen soil infiltration, based on both field observations and thermodynamic principles. Research in permafrost regions includes the exfiltration of groundwater in the seasonally thawed zone and the occurrence of perennial springs discharged from below the permafrost. Groundwater discharge is important to features such as icings and the occurrence of wetlands in a polar desert. Processes governing runoff generation on hillslopes have been examined, both in continuous and discontinuous permafrost zones. In terms of future research directions, consideration should be given to continued intensive field studies of cold region hydrological processes and the incorporation of these processes into aquatic chemistry and hydrological models and land surface schemes used in atmospheric models. A better understanding of the role of hydrological boundaries in affecting the rates of processes is needed. The question of scaling processes up from the small scale at which they are relatively well understood, to the larger scales necessary to address global environmental concerns also should be addressed.
Litong Zhao - One of the best experts on this subject based on the ideXlab platform.
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Influence of soil texture on snowmelt infiltration into Frozen Soils
Canadian Journal of Soil Science, 2002Co-Authors: Litong Zhao, D M Gray, B TothAbstract:This paper describes the influence of soil texture on snowmelt infiltration into Frozen Soils. Field data collected on Frozen, unsaturated agricultural Soils of the Canadian Prairies during snow ablation demonstrate: (a) poor association between the amount of infiltration of meltwater released by the seasonal snowcover and soil texture, and (b) small differences in cumulative amounts among Soils of widely different textures. A physics-based numerical simulation of heat and mass transfers with phase changes in Frozen Soils is used to study the mechanics of the infiltration process in representative clay, silty clay loam, silt loam and sandy loam Soils. The results of the simulations show that the differences among cumulative snowmelt infiltration into clay, silty clay loam and silt loam Soils after 24 h of continuous infiltration are small. Infiltration into a lighter-textured sandy loam after 24 h was on average 23% higher than in the other three Soils with most of the increase occurring in the first 5 h ...
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estimating areal snowmelt infiltration into Frozen Soils
Hydrological Processes, 2001Co-Authors: D M Gray, Litong Zhao, B Toth, J W Pomeroy, R J GrangerAbstract:An algorithm for estimating areal snowmelt infiltration into Frozen Soils is developed. Frozen Soils are grouped into classes according to surface entry condition as: (a) Restricted-water entry is impeded by surface conditions, (b) Limited-capillary flow predominates and water entry is influenced primarily by soil physical properties, and (c) Unlimited-gravity flow predominates and most of the meltwater infiltrates. For Limited Soils cumulative infiltration over time is estimated by a parametric equation from surface saturation, initial soil moisture content (water + ice), initial soil temperature and infiltration opportunity time. Total infiltration into Unlimited and Limited Soils is constrained by the available water storage capacity. This constraint is also used to determine when Limited Soils have thawed. The minimum spatial scale of the infiltration model is established for Limited Soils by the variabilities in surface saturation, snow water equivalent, soil infiltrability, soil moisture (water + ice) and depth of soil freezing. Since snowmelt infiltration is influenced by other processes and factors that affect snow ablation, it is assumed that the infiltrability spatial scale should be consistent with the scales used to describe these variables. For open, northern, cold regions the following order in spatial scales is hypothesized: Frozen ground > snowmelt > snow water equivalent ≥ Frozen soil infiltrability > soil moisture (water + ice) and snow water. For mesoscale application of the infiltration model it is recommended that the infiltrability scale be taken equal to the scale used to describe the areal extent and distribution of the water equivalent of the snowcover that covers Frozen ground. Scaling the infiltrability of Frozen Soils in this manner allows one to exploit established landscape-stratification methodology used to derive snow accumulation means and distribution. Scaling of soil infiltrability at small scales (microscale) is complicated and requires information on the association(s) between the spatial distributions of soil moisture (water + ice) and snow water. A flow chart of the algorithm is presented.
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estimating snowmelt infiltration into Frozen Soils
Hydrological Processes, 1999Co-Authors: Litong Zhao, Donald H GrayAbstract:A general parametric correlation for estimating snowmelt infiltration into Frozen Soils is developed using the results from a numerical model, HAWTS. This model includes a set of partial differential equations that describe water and heat transport with phase changes in Frozen Soils. The model was run for Soils with average textures ranging from sandy loam to clay. The relationship proposed relates infiltration to the total soil moisture saturation (water+ice) and temperature at the start of snow ablation, the soil surface saturation during melting, and the infiltration opportunity time—the time that meltwater is available at the soil surface for infiltration. The expression is calibrated to predict snowmelt infiltration in boreal forest and prairie environments. Comparisons of estimates of infiltration by the empirical relationship with those determined by field measurement suggest that the correlation will provide acceptable estimates of snowmelt infiltration into Frozen mineral Soils for use in operational hydrology schemes. Copyright © 1999 John Wiley & Sons, Ltd.
