Soil thermal conductivity and its influencing factors at the Tanggula permafrost region on the Qinghai–Tibet Plateau

Li, Ren; Zhao, Lin; Wu, Tonghua; Wang, Qinxue; Ding, Yongjian; Yao, Jimin; Wu, Xiaodong; Hu, Guojie; Xiao, Yao; Du, Yizhen; Zhu, Xiaofan; Qin, Yanhui; Yang, Shengli; Bai, Rui; Du, Erji; Liu, Guangyue; Zou, Defu; Qiao, Yongping; Shi, Jianzong

doi:10.1016/j.agrformet.2018.10.011

Cited by 68 publications

(39 citation statements)

References 40 publications

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“…8 During TP, the ice in pore phase to liquid water, which absorbs a large amount of heat, and the λ will be abrupt, and under these circumstances, the thawing time is extended. 29 The ground temperature increment of 30 cm layer was larger than that of the asphalt pavement. AC-16 layer and base layer (10~15 depth layer) thawed before the AC-13 layer.…”

Section: Thermal Properties and Thawingfreezing Processesmentioning

confidence: 88%

“…The change range in ground temperature below 30 cm depth was higher than that of the cement-stabilized sand under the same heat flux. 29 The ground temperature increment of 30 cm layer was larger than that of the asphalt pavement. We observed that the 30 cm depth soil layer thawed 3 days earlier than the asphalt pavement structure.…”

Section: Thermal Properties and Thawingfreezing Processesmentioning

confidence: 88%

“…According to the heat conduction theory, when the G and the transfer depth (distance) are constant, the λ is inversely proportional to the amount of temperature change that occurs within a given depth range, 29 meaning that the G decreases with an increase in depth. 8 During TP, the ice in pore phase to liquid water, which absorbs a large amount of heat, and the λ will be abrupt, and under these circumstances, the thawing time is extended.…”

Section: Thermal Properties and Thawingfreezing Processesmentioning

confidence: 99%

“…In the roadbed, liquid water migrates to cold sections, whereas vapor migrates to warm sections. 4,29 The ground temperature from the shallow to deep layers under the original pavement was in a "warm-cold-warm" state. Liquid water in soil layers at the depths of 10-30 cm accumulated at the depth of 20 cm.…”

Section: Liquid Water Migration and Vapor Condensationmentioning

confidence: 99%

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Hydrothermal accumulation under asphalt pavement in cold regions

Zhang

et al. 2019

Energy Science & Engineering

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Water and heat changes are the main problems that plague the stability and service performance of roadbeds in cold regions. Though hydrothermal transfer and accumulation directly affect roadbed properties, these processes remain poorly understood as monitoring data are often collected over short time periods and large spacing in depth. This research compares water and temperature data collected from 2012 to 2015 to elucidate the physical mechanisms of hydrothermal accumulation under both asphalt pavement and original pavement. These thermal and physical mechanisms include differences in the freezing process (FP) and the thawing process (TP), water transport, condensation, and hydrothermal accumulation. For instance, when compared to the underlying layer, the thawing of the surface layer of asphalt pavement was delayed by 35 days because of differences in hydrothermal properties. During TP, liquid water content changes from 3.31%‐13.2% to 15%‐37.67%, and the unfrozen water content of the soil layers under the asphalt pavement was approximately 6.85%‐12.34% higher than that of the soil layers under the original pavement. A layer with high water content and heat formed under the surface layer of asphalt pavement and provided the appropriate conditions for vapor transport and condensation. Soil layers thawed early in the preceding year, and this hydrothermal accumulation occurred on an annual basis. The annual minimum monthly average temperature was thus found to be increasing at the rate of 0.34°C/y. As water content also accounts for heat accumulation and was found to be more sensitive to change than temperature, the results of this study can provide theoretical and technical data useful for highway construction and design in permafrost regions.

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Section: Thermal Properties and Thawingfreezing Processesmentioning

confidence: 88%

Section: Thermal Properties and Thawingfreezing Processesmentioning

confidence: 88%

Section: Thermal Properties and Thawingfreezing Processesmentioning

confidence: 99%

Section: Liquid Water Migration and Vapor Condensationmentioning

confidence: 99%

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Hydrothermal accumulation under asphalt pavement in cold regions

Zhang

et al. 2019

Energy Science & Engineering

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“…Using experimental measures of soil heat flux and soil temperature, several authors estimated the soil thermal conductivity by isolating λ in Equation (2). However, this procedure can lead to possible numerical divergences, as shown by Li et al [19,30] that eliminated data when soil temperature gradient or soil heat flux is very close to zero to avoid this problem.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Model to Estimate the Soil Thermal Conductivity Using Field Experimental Data

et al. 2019

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Soil thermal conductivity is an important parameter for understanding soil heat transfer. It is difficult to measure in situ with available instruments. This work aims to propose a numerical model to estimate the thermal conductivity from the experimental measurements of soil heat flux and soil temperature. The new numerical model is based on the Fourier Law adding a constant empirical parameter to minimize the uncertainties contained in the data from field experiments. Numerically, the soil thermal conductivity is obtained by experimental linear data fitting by the Least Squares Method (LSM). This method avoids numerical indetermination when the soil temperature gradient or soil heat flux is very close to zero. The new model is tested against the different numerical methodology to estimate the soil heat flux and validated with field experimental data. The results indicate that the proposed model represents the experimental data satisfactorily. In addition, we show the influence of the different methodologies on evaluating the dependence of the thermal conductivity on the soil water content.

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The impact of changing subcanopy radiation on snowmelt in a disturbed coniferous forest

Hotovy

Jeníček

2020

Hydrological Processes

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Understanding the role of forests on snowmelt processes enables better estimates of snow storages at a catchment scale and contributes to a higher accuracy of spring flood forecasting. A coniferous forest modifies the snowpack energy balance by reducing the total amount of solar shortwave radiation (SWR) and enhancing the role of longwave radiation (LWR) emitted by trees. This study focuses on changes in SWR and LWR at three sites with different canopy structure (Bohemian Forest, Czechia), including one site affected by the bark beetle (Ips typographus). Measurements of incoming and outgoing SWR and LWR were performed at all sites equipped with CNR4 Net Radiometers for three cold seasons. In addition to SWR and LWR, sensible and latent heat, and ground heat and energy supplied by liquid precipitation were calculated. The results showed that net SWR at the healthy forest site represented only 7% of the amount at the open site due to the shading effect of trees. In contrast, net LWR represented a positive component of the snowpack energy balance at the healthy forest site and thus contributed the most to snowmelt. However, the modelled snowmelt rates were significantly lower in the forest than in the open area since the higher LWR in the forest did not compensated for the lower SWR. The progressive decay of disturbed forest caused the decrease in mean net LWR from −3.1 W/ m 2 to −12.9 W/m 2 and the increase in mean net SWR from 31.6 W/m 2 to 96.2 W/ m 2 during the study period. These changes caused an increase in modelled snowmelt rates by 50% in the disturbed forest, compared to the healthy forest site, during the study period. Our findings have important implications for runoff from areas affected by land cover changes due to either human activity or climate change.

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Soil thermal conductivity and its influencing factors at the Tanggula permafrost region on the Qinghai–Tibet Plateau

Cited by 68 publications

References 40 publications

Hydrothermal accumulation under asphalt pavement in cold regions

Hydrothermal accumulation under asphalt pavement in cold regions

A Numerical Model to Estimate the Soil Thermal Conductivity Using Field Experimental Data

The impact of changing subcanopy radiation on snowmelt in a disturbed coniferous forest

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