Depth Of Soil Freezing Research Articles

Развитие модели динамики снежного покрова Гидрометцентра России

Conceptual models of runoff formation used in the operational practice of hydrological forecasting by the Hydrometeorological Center of Russia include simplified parameterization of snow cover dynamics based on the use of snow cover melting coefficient, water-retaining capacity of snow and secondary freezing of meltwater in case of return of negative air temperatures. This schematization of the process is well established for the reliable calculation of the snow water equivalent for subsequent use in the calculation of meltwater inflow to the catchment surface and the calculation of streamflow characteristics. At the same time, the lack of calculation of snow density and snow height in the used schematization restricts the use of schemes for calculating of soil freezing depth in hydrological models, which seems to be extremely important for modelling runoff on mid-latitudes rivers, i.e. for the most Russian rivers. To overcome this disadvantage, the snow density and snow height parameterization was added to the calculation scheme of the model, which was verified using Roshydromet’s snow measurement routes data and shown a good and satisfactory quality of modeling of model characteristics.

A critical assessment of geological weighing lysimeters: Part 2—Modelling field scale soil moisture storage and hydrological fluxes

AbstractLand surface models (LSMs) are used to simulate the terrestrial component of water, energy, and biogeochemical cycles. These simulations are useful for water resources management, drought and flood prediction, and numerical climate/weather prediction. However, the usefulness of LSMs are dependent by their ability to reproduce states and fluxes realistically. Accurate measurements of water storage are useful to calibrate and validate LSMs outputs. Geological weighing lysimeters (GWLs) are instruments that can provide field‐scale estimates of integrated total water storage within a soil profile. We use field estimates of total water storage and subsurface storage to critically evaluate two different land surface models: the Modélisation Environnementale communautaire—Surface Hydrology (MESH) which uses the Canadian Land Surface Scheme (CLASS), and the Structure for Unifying Multiple Modeling Alternatives: (SUMMA). These models have differences in how the processes and properties of the land surface are represented. We attempted to parameterize each model in an equivalent manner, to minimize model differences. Both models were able to reproduce observations of total water storage and subsurface storage reasonably well. However, there were inconsistencies in the simulated timing of snowmelt; depth of soil freezing; total evapotranspiration; partitioning of evaporation between soil evaporation and evaporation of intercepted water; and soil drainage. No one model emerged as better overall, though each model had specific strengths and weaknesses that we describe. Insights from this study can be used to improve model physics and performance.

Freezing and thawing characteristics of seasonally frozen ground across China

Observations from 1,047 meteorological stations from September 1, 2006 to August 31, 2015 revealed regional differences in the freezing and thawing processes of seasonally frozen ground (SFG) across China. SFG generally undergoes a one-way freezing process (i.e., top-down), and the stations with a large freeze depth generally experienced long freeze durations. During the thawing process, soil is generally characterized by two-way thawing (i.e., top-down and bottom-up) in the region north of 35′N, especially north of 30′N (except in northeastern China). The onset of thawing from the bottom occurs earlier than that from the top at most stations in the two-way thawing region. The stations exhibiting one-way thawing (i.e., bottom-up) were mainly located on the southern edge of eastern China (east of 110°E) and in southern part of Xinjiang and southeast part of the Qinghai–Tibet Plateau. The freezing process lasts several days to more than four months longer than the soil thawing process, and this difference tends to be larger in high-latitude and high-altitude regions. All of the sites experienced a discontinuous freeze–thaw process, the station-average duration of which was less than a quarter of that of the continuous freeze–thaw process. Strong associations of soil freeze depth with air temperature (as characterized by the air freezing index and air thawing index) implied a dominant influence of air temperature on the soil freeze–thaw process. During the freezing process, this relationship was partially modulated by snow cover in snowy regions, such as northeast China, northwest China, and the eastern Tibetan Plateau. This paper provides the first overview of regional differences in the freezing and thawing processes of SFG over China, and the findings improve our understanding of the soil freeze–thaw process and provide important information to support research into regional landscapes, ecosystems, and hydrological processes.

Использование экзотермической реакции гашения извести для локального оттаивания сезонномерзлых грунтов

The the results of scientific and experimental work are described, the purpose of which was to determine the depth of thawing of seasonally frozen soils using the lime extinguishing reaction as a source of heat. The analysis of meteorological, agrometeorological conditions typical for Uralsk was carried out. The method, which provides an opportunity to use the heat released in the interaction of calcium oxide with water, was developed. To implement this method, a heat-insulating structure is designed and manufactured, which allows to accumulate and direct the accumulated heat through the heating system «from top to bottom». It was found that the use of the described method makes it possible to achieve a thawing depth of the soil up to 56 cm. At the time of scientific-experimental work, this thawing depth indicator exceeded the actual depth of soil freezing

Calculation and numerical modeling of the effect of heat and mass transfer on the properties of pile foundations in seasonally freezing soils

The phenomenon of heat and mass transfer in seasonally freezing soils has a significant impact on the condition of pile foundations. Building structures constructed in such soils experience extremely negative consequences: frost heave, vibration dynamics, moisture mass transfer and soil weakening during the thawing. Seasonally freezing soils occupy most of the territory of Kazakhstan, and in most regions the depth of soil freezing exceeds 1.5 m, there are settlements where the index reaches 1.97 m (Semiyarka, East Kazakhstan region) and in the north of the country - 2.74 m (Arshaly, Akmola region). Arrangement of foundation bases below the frost depth leads to increased construction costs, requires additional costs for thermal insulation, ventilation, other materials and structures, and, in addition, does not always lead to a full levelling of the negative impact of heat and mass transfer on the term and conditions of operation of buildings, structures, railways and roads. Therefore, the efforts of engineers and specialists in the field of thermal physics are aimed at finding effective ways to solve the problems of deformation and destruction of foundations in seasonally freezing soils. In the article an attempt is made to reveal the character of heat and mass transfer influence on pile foundations in seasonally freezing soils on the basis of a thermomechanical model.

FACTORS OF SLOPE SPRING RUNOFF ON GRAY FOREST SOILS IN THE CENTRAL FOREST-STEPPE

The results of long-term studies of several generations of scientists at the Novosilskaya zonal agroforestry and reclamation experimental station named after A.S. Kozmenko (a branch of the Federal Research Center of Agroecology of the Russian Academy of Sciences), initiated by Professor G.P. Surmach, were summarized and analyzed. The task was to assess the nature of the spring slope runoff formation and show the role of natural factors and agricultural activities. The methodological basis of the research was the method of runoff sites. As a result of a long (64 year long) study, a number of important dependencies and features of the runoff formation under different natural and climatic conditions were identified, as well as the influence of natural factors and agricultural activities on it (structure of sown areas, cultivation history, tillage methods, etc.). Scientific materials on the elements of the spring water balance give an idea of their patterns. It has been established that only three natural factors out of a large number of them have a significant impact on the slope spring runoff, i. e. the depth of soil freezing, snow reserves and humidity of the upper soil layer (down to 30 cm). Other factors almost do not affect the amount of runoff and they could be ignored in the process of calculation. The limiting levels of these three factors have been established, under which no runoff is formed. During 64 years of study, runoff was absent for 33 years, ranging from 1 to 146 mm in other years. Among anthropogenic factors, tillage methods and the state of agricultural backgrounds have a profound influence. The runoff regulatory importance of finching and the runoff forming role of perennial grasses and winter crops are discussed. On average, runoff from compacted arable land was 10 mm higher compared to loose chick; in some years the difference was significantly greater. The results of the study are necessary for the design of erosion-control adaptive landscape farming system.

Projected changes in soil freeze depth and their eco-hydrological impacts over the Tibetan Plateau during the 21st century

In the context of global warming, the soil freeze depth (SFD) over the Tibetan Plateau (TP) has undergone significant changes, with a series of profound impacts on the hydrological cycle and ecosystem. The complex terrains and high elevations of the TP pose great challenges in data acquisition, presenting difficulties for studying SFD in this region. This study employs Stefan's solution and downscaled datasets from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to simulate the future SFDs over the TP. The changing trends of the projected SFDs under different Shared Socio-economic Pathways (SSP) scenarios are investigated, and; the responses of SFDs to potential climatic factors, such as temperature and precipitation, are analyzed. The potential impacts of SFD changes on eco-hydrological processes are analyzed based on the relationships between SFDs, the distribution of frozen ground, soil moisture, and the Normalized Difference Vegetation Index (NDVI). Results show that the projected SFDs of the TP are estimated to decrease at rates of 0.100 cm/yr under the SSP126, 0.330 cm/yr under the SSP245, 0.565 cm/yr under the SSP370, and 0.750 cm/yr under the SSP585. Additionally, the SFD decreased at a rate of 0.160 cm/yr during the historical period from 1950 to 2014, which was between the decreasing rates of the SSP126 and SSP245 scenarios. The projected SFDs are negatively correlated with air temperature and precipitation, more significant under the higher emissions scenario. The projected decrease in SFDs will significantly impact eco-hydrological processes. A rapid decrease in SFD may lead to a decline in soil moisture content and have adverse impacts on vegetation growth. This research provides valuable insights into the future changes in SFD on the TP and their impacts on eco-hydrological processes.

Latest potential sowing time of galega (Galega orientalis Lam.) for successful cultivation in the extreme winter conditions of northern Japan

AbstractMixed seeded plots of timothy (Phleum pratense L.) and galega (Galega orientalis Lam.) were established in multiple seeding times from 2014 to 2017 to determine the latest sowing limit in the Konsen region, northern Japan, where growing conditions are severe. Although low yields were observed in some cases when the soil freezing depth was deeper than average, the dry matter yield of the first crop of galega in the year after sowing was higher under conditions that ensured pre‐overwintering plant length growth of 30 cm or more, as compared with growth of less than 30 cm. Galega rhizomes were observed under conditions of pre‐overwintering plant length of 28 cm or more, but not under conditions of less than 28 cm in length. Therefore, achieving 30 cm plant length prior to overwintering is desirable when sowing galega in the Konsen region. Furthermore, the effective cumulative temperature (ECT) required for pre‐overwintering galega to reach 30 cm in plant length was 1079°C, for which seeding dates were calculated to be July 10 and June 29 in terms of calendar days, with 80% and 90% probability. In the Konsen region, galega should be sown earlier than in other regions of Hokkaido to ensure the growth rate because of the effects of soil freezing on overwintering performance.

Changes in Soil Freeze Depth in Response to Climatic Factors in the High-Latitude Regions of Northeast China

The changing climate in recent decades has caused rapid, widespread frozen ground degradation of the cryosphere, and changes in frozen ground may largely affect the ecosystem function. This study presents the long-term shrinkage of frozen ground, driven forces and resultant ecological impacts at three high-latitude sites (namely Nenjiang, Jiagedaqi, and Tahe, from low to high latitude) in Northeast China, an area that has received less attention in previous permafrost studies. As the key indicators of frozen ground, the ground surface and subsurface soil temperature (down to 40 cm) were found to increase in the period from the 1970s to the 2000s. The annual mean air temperatures at observation sites have increased significantly at rates of 0.24~0.40 °C/decade from 1971 to 2019, and were found to be negatively correlated to the change in soil freeze depth at the Jiagedaqi and Tahe sites. The annual snow depth at Jiagedaqi was found to decrease at a rate of 1.8 cm/decade, and positively correlate to the soil freezing index. The vegetation status of the three watersheds improved, as indicated by the increased normalized difference vegetation index (NDVI) from 2000 to 2017. Our results can make a valuable contribution to knowledge of climate–frozen ground interactions, and can highlight the importance of examining such interaction for permafrost protection in similar high-latitude permafrost-dominated basins.

Методы расчета глубины промерзания грунтов земляного полотна высокоскоростных магистралей в условиях холодного климата в КНР

Purpose: Methods for calculating soil freezing depth of high-speed railway subgrade are de-veloped given its multilayer structure. Methods: Existing methods for soil freezing depth calculation have been reviewed, advanced Berggren method for calculating soil freezing depth of HSR subgrade and numerically modeling method for subgrade temperature regime on the basis of mathematical model given moisture migration are proposed. The calculation reliability is confirmed by comparison with numerical simulation results and the results of the calculation by method based on Chinese and Russian railway construction standards. Re-sults: The results of soil freezing depth calculations by different methods are similar. It is reasonable to use advanced Berggren method to calculate soil freezing depth for multilayer system. Numerical modeling method makes it possible to predict soil freezing depth includ-ing depth change of freezing and thawing caused by climate warming. Practical signifi-cance: To calculate soil freezing depth of HSR subgrade, it is advisable to use advanced Berggren method. The developed model can be used both to study the logic of subgrade thermal regime distribution at freezing and thawing and to project the thickness of protec-tive layers against a frost for HSR subgrade construction.

Infl uence of ecological factors on the start date of the colorado potato beetle lLeptinotarsa decemlineata (Say) (Coleoptera, Chrysomelidae) emergence from overwintering sites in the Central forest-steppe priobskii agro-landscape region

As a result of long-term studies, the complex e ect of the depth of soil freezing, depth of snow cover, the amount of precipitation, the temperature of air and of soil at a depth of 0-20 and 20-40 cm, the sum of e ective temperatures on the start date of the adult Leptinotarsa decemlineata (Say) emergence from the soil in potato plantings was established in the Central Forest-Steppe Priobskii Agro-Landscape Region. The average values of these environmental factors for the period from September of the previous year to June of the current year by 27.2% determined the emergence date of the overwintered imago. The share of the conditions of the previous year in uence was 50.5, and the conditions of the current year, 31.1%. The appearance of the overwintered adults was delayed when they had gone for overwintering in moist and cool soil. In November, the emergence date begins to be a ected by the depth of snow cover and the depth of soil freezing (the in uence shares 86.8 and 79.5%, respectively), and their e ect together with the factors listed accounted for 35.3%. In December, the same trend was observed, but the air temperature was not considered. In January, the importance of the parameter of the soil temperature increased to 84.3%, and that of the complex of factors in 26.7% of cases. In February, the same trend was observed, and the share of the in uence all previously listed factors increased to 43.0%. From March, the impact of the depth of soil freezing and the depth of snow has decreased to 42.3%, and from April, the sum of rain precipitation and air temperature began to in uence in 81.8 and 65.8% of cases, respectively. In May, the start date of the pest appearance is a ected only by the soil temperature at a depth of 0-20 and 20-40 cm - 80.7 and 94.0%, respectively, and by photoperiod - 91.1%. In June, the main factors were the amount of rain precipitation and the soil temperature - 100%, while the impact of accumulated SET was 50.0%. Thus, in this region, on average, the beginning of the adults’ Exit from the soil starts on June 17 ± 12 days, when the average daily air temperature reaches +19.1 ± 5.8 °C, the sum of rain precipitation (at air temperature > 10 °C) - 70.7 ± 39.1 mm, and the soil at a depth of 0-20 and 20-40 cm warms up to +17.6 ± 3.8 °C and +14.8 ± 2.5 °C, respectively. The SET in this period is 149.0 ± 64.1 degree days.

Influence of global warming on hydrothermal indicators and overwintering of winter cereals in the conditions of Prysyvashsha

Topicality. Climate change due to global warming determines important and relevant areas of re-search activities at the current stage of agricultural development. Climate change affects the potential of natural resources therefore the limits of these changes are taken into account when determining the ways of agricultural production development. Purpose. To determine the impact of global warming as a result of changing climatic conditions on the overwintering of winter cereals in Prysyvashsha. Materials and Methods. The research materials were long-term observations of the basic climatic indicators at the Heni-chesk Experimental Station of the SE Institute of Grain Crops of NAAS. Results. Changes of the main climatic indicators against the background of global warming in Prysyvashsha for the 2004–2020 were analyzed. During 2015–2018, the soil freezing depth and the minimum temperature at the depth of the tillering node of winter cereals during the winter period were investigated. An increase in the average annual air temperature was recorded, which caused a decrease in the soil freezing depth and an increase in its temperature at the depth of the tillering node and shortening of the winter period. Conclusions. According to the results of the study, there is an essential need to find more optimal dates for sowing winter wheat and barley as one of the key segments of agrotechnical measures, which provides better adaptation of winter crops and increase their productivity when grown in new environmental conditions in the arid Steppe zone of Ukraine. Key words: global warming, climate change, air temperature, soil temperature, precipitation, winter wheat, winter barley, sowing dates, depth of soil freezing

ЭРОЗИОННЫЕ ПРОЦЕССЫ ПРИ СТОКЕ ТАЛЫХ ВОД НА ЮГЕ ЕВРОПЕЙСКОЙ ЧАСТИ РОССИИ

Purpose: to determine the regularities of melt water runoff and soil erosion on the chernozems of Rostov region for a long-term observation period of 1970–2021. Methods. Field experiments were carried out on slopes on compacted arable land (perennial and winter crops) and loose arable land (autumn ploughing). Measuring of melt water runoff and precipitation during the period of snow melting and soil washout was carried out on the water balance site of Stepnoy village Rostov region. The main physical and water-physical properties of soil during the snow melting period (freezing depth, moisture content of the upper soil layer 0.30 cm, water permeability) were studied according to generally accepted methods. Results. An analysis of field observations for the period from 1970 to 2021 was carried out for the parameter “snow water reserves before melting + precipitation during the snow melting period”, which averaged 47.8 mm over 52 years on compacted arable land and 43.15 mm on loose arable land, the runoff coefficient was higher on compacted arable land and amounted to 0.25 and 0.10, respectively; with appearance of surface runoff of 10.6 t/ha, this indicator increased to 5.9 and 20.7 t/ha on loose arable land, respectively. Mathematical analysis of the data made it possible to establish the relationship between the values of runoff, soil washout and water reserves in snow, the depth of soil freezing and water permeability during the runoff period. Conclusions. Long-term studies (52 years) found that there is a greater accumulation of water in snow on compacted arable land than on loose arable land, while the runoff coefficient was 2.5 times higher on compacted arable land, but the plants retain soil particles on compacted arable land, and soil washout on average over the years with the manifestation of surface runoff, was 10.6 t/ha, while on loose arable land this figure increased to 20.7 t/ha. The relationship between runoff rate, soil washout and water reserves in snow, the depth of soil freezing and water permeability during the runoff has been determined.

Особенности проявления эрозии в пределах овражно-балочного водосбора

Purpose: to determine patterns of formation of hydrographic network elements depending on the melt-and rainwater runoff and soil losses. Materials and methods. The studies were carried out in the upper reaches of the Bolshoy Log gully system, which is a part of the land use of the experimental farm “Polevoy” of the Federal Rostov Agrarian Research Center, with an area of 2070 hectares, of which more than 70 % is arable land. Soils are ordinary chernozems of varying degrees of erosion. The standard methods of research and the method of pins were used on runoff plots. Results. Within the catchment area, the amount of runoff and hydraulic indicators of water courses are greatly influenced by the agricultural background and the soil surface condition from which meltwater flows, and the intensity of erosion processes is influenced by the depth of soil freezing, the moisture content of topsoil, water storage in snow, snowmelt intensity. The water sprays are concentrated along the gullies, where the soil is washed out over time, and they pass into the category of hollows, then into ravines and gullies, forming a hydrographic network in the gully-ravine catchment area. The most intensive meltwater runoff was observed over the years: in 1988 – 33.8 mm, 2003 – 63.9 mm, 2006 – 24.6 mm, 2014 – 14.3 mm, 2017 – 19.3 mm, 2023 – 10–14 mm. In the variants with reclamation protective forest plantations and hydraulic structures, the runoff was 5–12 mm less than in the control and it retained in the forest belt. The mathematical data analysis made it possible to determine the relationship between the runoff rate and soil loss in the gully-ravine catchment, depending on the distance from the watershed. Conclusions. On the gully-ravine catchment, the sheet wash smoothly turns into a linear one and forms hollows and valleys. The final link of the catchment area are ravines and gullies. During the peak periods of meltwaters, the water flow velocity on flat sections of the slope is 0.33–0.46 m/s, and along the hollows – 0.57–0.83 m/s.

WEATHER CONDITIONS DURING THE CONSTRUCTION OF DEFENSIVE LINES IN CHUVASHIA DURING THE GREAT PATRIOTIC WAR

Based on archival materials and scientific literature, the article studies weather conditions in the territory of the Chuvash Republic during the construction of defensive lines during the Great Patriotic War. The relevance of the chosen topic is due to insufficient exploration degree of this aspect in the scientific literature. The novelty of the research consists in attracting new sources: tables of meteorological and agro-meteorological observations TM-1 and BSH-1 made by meteorological stations of Alatyr, Kanash, Poretskoye, Cheboksary in late 1941 – early 1942. The purpose of the work is to study the air temperature values, snow cover height and soil freezing depth in Chuvashia in the winter of 1941–1942 based on the analysis of different groups of historical sources: 1) documents of the authorities controlling the progress of construction; 2) memories of the builders of defensive lines and their relatives; 3) observation data of air temperature, precipitation, snow cover height, depth of soil freezing compiled by weather stations in the territory of the republic and in neighboring cities. Comparison of information obtained from different sources helped to conclude about their reliability and determine in what weather conditions the construction of defensive structures in the territory of the republic took place during the Great Patriotic War. Comparison of historical sources of different groups does not confirm the data on the air temperature below –44°C during the construction period in the territory of Chuvashia. It should be taken into consideration that the minimum temperature indicators refer to the night time when the work was not carried out. The construction lasted a long time, and if we keep in mind the period from October 1941 to February 1942, then the weather was different within these time limits and it is impossible to accurately define only one value of air temperature. It can be unequivocally stated that winter of 1941–1942 was one of the coldest in the XX century.

Математическое моделирование процесса промерзания грунтов земляного полотна железных дорог в условиях холодного климата

Purpose: Mathematical model for studying the process of soil freezing given moisture migration is developed. Numerical modeling of temperature mode of railway subgrade at non-stationary pro-cess in cold climate conditions is performed. Methods: Numerical implementation of the model is performed by mathematical module processing in COMSOL Multiphysics program, which’s based on partial differential equations (PDE), with finite element method. The model reliability is con-firmed by the comparison with previous experimental data and the results of simulation by other authors. Results: Calculation results on the developed model basis show the best correlation with experimental data in comparison with the results for other models. Calculation example and calcu-lation results for subgrade temperature mode in freezing-thawing fifth cycle are presented. The analysis of soil freezing depth change and soil temperature fluctuation change by depth by fifth year are carried out. Practical significance: The developed mathematical model makes it possible to predict soil freezing depth, taking into account moisture migration, including freezing and thawing depth changes caused by climate warming. The developed model can be used both, to study the mechanism of subgrade temperature mode distribution at freezing and thawing, and to improve subgrade construction for to protect it from soil frost heaving.

Estimation of Soil Freeze Depth in Typical Snowy Regions Using Reanalysis Dataset: A Case Study in Heilongjiang Province, China

Soil freeze depth variations greatly affect energy exchange, carbon exchange, ecosystem diversity, and the water cycle. Given the importance of these processes, obtaining freeze depth data over large scales is an important focus of research. This paper presents a simple empirical algorithm to estimate the maximum seasonally frozen depth (MSFD) of seasonally frozen ground (SFG) in snowy regions. First, the potential influences of driving factors on the MSFD variations were quantified in the baseline period (1981–2010) based on the 26 meteorological stations within and around the SFG region of Heilongjiang province. The three variables that contributed more than 10% to MSFD variations (i.e., air freezing index, annual mean snow depth, and snow cover days) were considered in the analysis. A simple multiple linear regression to estimate soil freeze depth was fitted (1981–2010) and verified (1975–1980 and 2011–2014) using ground station observations. Compared with the commonly used simplified Stefan solution, this multiple linear regression produced superior freeze depth estimations, with the mean absolute error and root mean square error of the station average reduced by over 20%. By utilizing this empirical algorithm and the ERA5-Land reanalysis dataset, the multi-year average MSFD (1981–2010) was 132 cm, ranging from 52 cm to 186 cm, and MSFD anomaly exhibited a significant decreasing trend, at a rate of −0.38 cm/decade or a net change of −28.14 cm from 1950–2021. This study provided a practical approach to model the soil freeze depth of SFG over a large scale in snowy regions and emphasized the importance of considering snow cover variables in analyzing and estimating soil freeze depth.

Dynamics of soil freezing and thawing in the agroforestry landscape

The article presents the dynamics of soil freezing and thawing in the agroforestry landscape of the dry-steppe zone. These processes in winters with unstable snow cover have their own characteristics. The purpose of this study was to investigate the character of soil freezing and thawing in the agroforestry landscape under conditions of low snowfall winters. Observations were carried out in the winter period of 2020–2021 at the existing runoff-erosion research station in Volgograd. The dynamics of soil freezing and thawing was studied using Danilin freeze-thaw meters installed in the field and in the center of a four-row forest belt. Simultaneously, snow cover height was measured in triplicate with a snow measuring rod. The weather conditions were characterized by alternating thaws, which promoted snow cover melt, and frosts, which increased the depth of soil freezing. The formation of a 10-15 cm snow cover did not affect soil freezing. In the absence of snow on the background of a brief thaw, the lower boundary of the frozen layer in the field decreased by 11 cm compared to the forest belt, which even in the leafless state affected the inflow of solar thermal energy. Average freezing at the end of winter was 85 cm in the field and 67 cm in the forest belt. Thawing in the field was faster. During the first two weeks, the rate of soil thawing averaged 2.3 cm/day in the field and 1.3 cm/day in the forest belt. After that, the depth of freezing in the whole agroforestry landscape became equal. During the next two weeks, the thawing rate doubled. After complete soil thawing in the field in the forest belt, the thickness of the frozen layer averaged 32 cm.

Influence of snow cover on soil freeze depth across China

Using 1980–2014 observation data of 378 meteorological stations, this study quantified the correlations between snow cover and the annual maximum seasonally freeze depth (MSFD) across China and the contributions of snow cover to MSFD. Snow cover exhibited a weak effect on MSFD across China, which may be related to the thinness and short duration of the snow cover. Regional differences in the effects of snow cover on MSFD were relatively large, and the effects of snow cover were more significant than those of air temperature (characterized by the air-freezing index) at stations in Northeast China, northeastern Inner Mongolia, and the north of the Tianshan Mountains. In regions with a thin snow cover or short snow cover duration (SCD), the cooling effect of snow cover can dominate, but it only slightly influences MSFD owing to the short SCD. With increasing average snow depth (ASD) and SCD, the relative contributions of snow cover to MSFD gradually increased, peaking at SCDs of 120–140 days or ASDs of 8–10 cm, which is attributable to the increasing insulating effect. However, with further increase in ASD and SCD, the insulating effect decreases because of high albedo and the latent heat effect of snow melting. This decrease resulted in declining MSFD–snow cover correlations and snow cover contributions to MSFD. Compared with SCD, ASD has a greater influence on MSFD. By adding an ASD variable to the Stefan formula, this modified formula outperformed the conventional formula in MSFD estimation at SCDs of 60–140 days. This study demonstrated the importance of snow cover variables for soil freeze depth analysis and simulation in areas with large snow cover and further elucidated the effects of snow cover on soil freeze depth.

Application of the calculating scheme for rock freezing depth during geotechnical monitoring on the Anzob pass (Tajikistan)

Rock instability in high-altitude areas is an important risk factor for humans and infrastructure, especially in the context of climate change. The presence of water in the rock leads to a clear increase in the strength of the rock, the effect is enhanced at lower temperatures and a higher degree of saturation. Since the decrease in rock strength due to the phase transition from frozen to thawed state has a great impact on the strength and stability of the rock soil, the paper proposes a model and a numerical method for estimating the depth of rock soil freezing based on data on air temperature and the thickness of the snow cover. The paper also evaluates the effect of air temperature and snow cover on the rock soil stability and depth of freezing according to the proposed calculation algorithm which is applied for the winter periods 2010/2011-2019/2020 at the Anzob pass in Tajikistan. The calculating scheme is constructed according to the three-layer medium thermal conductivity problem (snow, frozen and thawed rock) with a phase transition on the boundary frozen and thawed rock soil. The equation of heat balance contains the heat of the phase transition, the energy of inflow from the thawed rock and the outflow into the frozen rock and, in the presence of snow cover, the outflow into the atmosphere air through it.