Model of the influence of snow cover on soil freezing (original) (raw)
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Winter regime of temperature and snow accumulation as a factor of ground freezing depth variations
E3S Web of Conferences, 2020
The observations of ground freezing depth in the conditions of bare soil and under natural cover have been carried out at the sites of meteorological observatory of Lomonosov Moscow State University since the observatory’s foundation in 1954. For estimation of role of snow cover in variations of ground freezing depth the calculations of ground freezing depth were conducted using the meteorological data on air temperature and snow thickness for winter seasons of 2011/12-2018/19. The calculating scheme for ground freezing is constructed on the basis of three layer media heat conductivity problem (snow cover, frozen and thawed ground) with phase transition on the boundary of frozen and unfrozen ground. Heat balance equation includes phase transition energy, inflow of heat from unfrozen ground and outflow to frozen ground, snow cover and atmosphere. The heat flux is calculated on the basis of Fourier law as a product of heat conductivity and temperature gradient. It is supposed, that th...
Acta Geotechnica
This research work presents an experimental and numerical study of the coupled thermo-hydro-mechanical (THM) processes that occur during soil freezing. With focusing on the artificial ground freezing (AGF) technology, a new testing device is built, which considers a variety of AGF-related boundary conditions and different freezing directions. In the conducted experiments, a distinction is made between two thermal states: (1) The thermal transient state, which is associated with ice penetration, small deformations, and insignificant water suction. (2) The thermal (quasi-) steady state, which has a much longer duration and is associated with significant ice lens formation due to water suction. In the numerical modeling, a special focus is laid on the processes that occur during the thermal transient state. Besides, a demonstration of the micro-cryo-suction mechanism and its realization in the continuum model through a phenomenological retention-curve-like formulation is presented. Thi...
E3S Web of Conferences, 2020
According to developed algorithm and calculating scheme the calculations of ground freezing depth variations for observation sites of meteorological stations of Moscow region (Mozhaysk, Kolomna) were performed on basis of meteorological data on air temperature and snow cover thickness for winter periods of 1988/89-2018/19. The comparison of calculated and available in open access observation data on ground freezing depth for these winter periods was also conducted and indicated good correspondence. The calculating scheme for ground freezing is constructed on basis of three layer media heat conductivity problem (snow cover, frozen and thawed ground) with phase transition on the boundary of frozen and unfrozen ground. Heat balance equation includes phase transition energy, inflow of heat from unfrozen ground and outflow to frozen ground, snow cover and atmosphere. The heat flux is calculated on basis of Fourier law as a product of heat conductivity and temperature gradient. It is supp...
Effect of snow cover on soil frost penetration
Contributions to Geophysics and Geodesy, 2017
Snow cover occurrence affects wintering and lives of organisms because it has a significant effect on soil frost penetration. An analysis of the dependence of soil frost penetration and snow depth between November and March was performed using data from 12 automated climatological stations located in Southern Moravia, with a minimum period of measurement of 5 years since 2001, which belong to the Czech Hydrometeorological institute. The soil temperatures at 5 cm depth fluctuate much less in the presence of snow cover. In contrast, the effect of snow cover on the air temperature at 2 m height is only very small. During clear sky conditions and no snow cover, soil can warm up substantially and the soil temperature range can be even higher than the range of air temperature at 2 m height. The actual height of snow is also important – increased snow depth means lower soil temperature range. However, even just 1 cm snow depth substantially lowers the soil temperature range and it can ther...
A constitutive model of saturated soils for frost heave simulations
Cold Regions Science and Technology, 1993
It is argued that the volume increase of frost-susceptible soils due to ice growth during freezing can be described by a phenomenological model without resorting to the micromechanical processes causing the ice growth. Judging from solid mechanics' experience, such model may prove to be more accurate in predictions of frost heave than models based on micromechanical processes (single ice lens formation). A particular model based on a porosity rate function is described. This approach, suggested earlier by Blanchard and Fr~mond (1985), is extended to include more factors affecting ice growth during freezing of frost susceptible soils. Results of simulations of a one-dimensional freezing process are shown to illustrate the main features of the model and its potential applicability. Although a quantitative verification of the model was not possible, as sufficient data from lab tests were not available to calibrate it, the numerical results indicate a very realistic response of samples to simulated freezing processes.
Development of a land surface model with coupled snow and frozen soil physics
Water Resources Research, 2017
Snow and frozen soil are important factors that influence terrestrial water and energy balances through snowpack accumulation and melt and soil freeze-thaw. In this study, a new land surface model (LSM) with coupled snow and frozen soil physics was developed based on a hydrologically improved LSM (HydroSiB2). First, an energy-balance-based three-layer snow model was incorporated into HydroSiB2 (hereafter HydroSiB2-S) to provide an improved description of the internal processes of the snow pack. Second, a universal and simplified soil model was coupled with HydroSiB2-S to depict soil water freezing and thawing (hereafter HydroSiB2-SF). In order to avoid the instability caused by the uncertainty in estimating water phase changes, enthalpy was adopted as a prognostic variable instead of snow/soil temperature in the energy balance equation of the snow/frozen soil module. The newly developed models were then carefully evaluated at two typical sites of the Tibetan Plateau (TP) (one snow covered and the other snow free, both with underlying frozen soil). At the snow-covered site in northeastern TP (DY), HydroSiB2-SF demonstrated significant improvements over HydroSiB2-F (same as HydroSiB2-SF but using the original single-layer snow module of HydroSiB2), showing the importance of snow internal processes in three-layer snow parameteri-zation. At the snow-free site in southwestern TP (Ngari), HydroSiB2-SF reasonably simulated soil water phase changes while HydroSiB2-S did not, indicating the crucial role of frozen soil parameterization in depicting the soil thermal and water dynamics. Finally, HydroSiB2-SF proved to be capable of simulating upward moisture fluxes toward the freezing front from the underlying soil layers in winter.
[1] A dramatic reduction in soil frost depth has been reported for Hokkaido Island of northern Japan over the last 20 years. Since soil frost strongly affects snowmelt infiltration and runoff, the reduction in frost depth may have altered the water and nutrient cycles in this region. A paired‐plot experiment was conducted in an agricultural field in Tokachi, Hokkaido, to compare the movement of soil water at different frost depths, controlled by manipulating the depth of snow cover. Snow was removed to enhance soil freezing in the treatment plot and was undisturbed in the control plot. The soil froze to a maximum depth of 0.43 m under the treatment plot and 0.11 m under the control plot. During the freezing period, the amount of upward soil water flux toward the freezing front in the treatment plot was more than double that in the control plot. During the snowmelt period, infiltration of meltwater was unimpeded by the thin frozen layer in the control plot, whereas the relatively thick frozen layer in the treatment plot impeded infiltration and generated 63 mm of runoff. These results clearly show that the changes in the timing and thickness of snow cover deposition can cause a dramatic reduction of frost depth and change in the soil water dynamics.
Analyses and development of a hierarchy of frozen soil models for cold region study
2010
Numerous frozen soil models currently in use differ in the complexity of their governing equations or/and in the processes being considered. It is important to comprehensively examine and categorize these on the basis of physical principles, assumptions, and relationship to each other. In this paper frozen soil models are classified into different levels according to the complexity of the governing equations.
An energy-conserving model of freezing variably-saturated soil
The Cryosphere Discussions, 2010
In this paper we provide a method for solving the energy equation in freezing soil. The solver is linked with the solution of Richards equation, and therefore able to approximate water movement near the liquid-solid phase transition. The equations show non-linear characteristics causing oscillatory behavior in the solution close to the phase 5 transition, when normal methods of iterative integration, as Newton or Picard, are used. Thus, a globally convergent Newton method has been implemented to achieve convergence. The method is tested by comparison with an analytical solution to the Stefan problem and by comparison with experimental data derived from literature. 25 the complete energy equation and in natural conditions are expected to provide the 1244 TCD best accuracy in simulating ground thawing and freezing . However, the treatment of latent heat is not an easy task because it is confined to a narrow range near the melting point, and thus represents a discontinuity that may create numerical oscillations . Numerical models usually treat the latent heat term using one of these approaches: (i) the pure conduction heat equation is first 5 solved, and then the soil temperature is readjusted by the ratio of liquid and solid water given by energy conservation during phase change (Shoop and Bigl, 1997); (ii) the latent heat term is related to temperature and unfrozen water content by an apparent heat capacity formulation . The objective of this paper is to describe a new formulation for a energy conserving freezing soil algorithm based on 10 the apparent heat capacity method which allows to cope with the high non-linearities introduced by the latent heat term. The algorithm is tested against the analytical solution of unilateral freezing of a semi-infinite region given by Neumann, and the experimental results published by .