scholarly journals Long-Term Thermal Regimes of Subgrade under a Drainage Channel in High-Altitudinal Permafrost Environment

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Hong Yu ◽  
Hongwu Han ◽  
Wei Ma ◽  
Zekun Ding ◽  
Ling Chen
Keyword(s):  
Moisture Transfer ◽  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Flowing Water ◽  
Drainage Channel ◽  
Thermal Regimes ◽  
Bottom Width ◽  
Heat And Moisture ◽  
The Impact

In permafrost regions, construction of a channel involves a large amount of excavation activities and changes to surface water body, which can exert great impacts on the thermal regimes of permafrost underlying. In this paper, a coupled mathematical model of heat and moisture transfer was constructed for freeze-thaw soils to investigate the long-term thermal regimes of subgrade beneath a drainage channel built on the Qinghai-Tibet Plateau. Based on the numerical simulations, the thermal regimes of the subgrade both in warm and cold seasons were analyzed within a period of 50 years, as well as the impact of the widths of the channel. The results showed that the channel excavation and flowing water within could lead to a significant underlying permafrost degradation. During the first 30 years, the permafrost beneath the channel mainly experienced a rapid downward degradation. After that, the lateral thermal erosion of the flowing water led to a rapid permafrost degradation beneath the slope of the channel. In cold seasons, the shallow ground beneath the channel would not refreeze due to the flowing water and the thaw bulb actually expanded throughout the year. For the channel with a bottom width of 15 m, the thaw bulb beneath the channel could expand laterally to the natural ground about 10 m far away from the slope shoulder of channel till the 50th year. With different widths, the long-term thermal regimes of the subgrade beneath the channels differed considerably and the maximum difference was at the slope toe of the embankment. With the numerical simulated results, it is recommended that a channel built on permafrost should be wide-and-shallow rather than narrow-and-deep if conditions permit.

Long-term Effects of Different Humidification Systems on Endotracheal Tube Patency

2004 ◽  
Vol 100 (4) ◽  
pp. 782-788 ◽  
Author(s):  
Samir Jaber ◽  
Jérôme Pigeot ◽  
Redouane Fodil ◽  
Salvatore Maggiore ◽  
Alain Harf ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Endotracheal Tube ◽  
Heated Humidifier ◽  
Long Term Effects ◽  
Moisture Exchanger ◽  
Acoustic Reflection ◽  
Heat And Moisture ◽  
The Impact

Background Accumulation of mucous secretions in an endotracheal tube (ETT) increases its resistance, and the amount of deposit may be affected by the quality of humidification and heating of the inspired gas. Methods The authors assessed the impact of two humidification systems, a heated humidifier (HH) and a hygroscopic-hydrophobic heat and moisture exchanger (HME), on the ETT patency in patients selected to require mechanical ventilation for more than 48 h. This comparison was performed over two consecutive periods and used the acoustic reflection method, which characterizes the amount and site of ETT obstruction and allows estimating ETT inner volume and resistance. Measurements were performed three times a week over the period of mechanical ventilation. Comparisons were performed at mid duration and at the end of the mechanical ventilation period. Results The HH was used in 34 patients, and the HME was used in 26 patients. The two groups had similar severity and duration of mechanical ventilation. At mid duration of mechanical ventilation (5.5 +/- 3.3 vs. 4.8 +/- 3.3 days; P = 0.4), no difference was observed in ETT volume and resistance between the two groups. At the end of the study period (10.5 +/- 5.8 vs. 9.6 +/- 6.3 days of mechanical ventilation; P = 0.4), ETT volume was reduced to a greater extent with HME than with HH (-3.3 +/- 2.9 vs. -5.1 +/- 2.5%; P = 0.008), and ETT resistance increased significantly more with the HME than with the HH (8.4 +/- 12.2 vs. 19.4 +/- 17.7%; P = 0.001). Conclusion Prolonged use of humidification systems results in progressive reduction of ETT patency, and to a greater extent with HMEs than with HHs.

Monitoring permafrost changes in the Yangtze River source region of the Qinghai-Tibetan Plateau using differential SAR interferometry

2020 ◽  
Author(s):  
Lingxiao Wang ◽  
Lin Zhao ◽  
Huayun Zhou ◽  
Shibo Liu ◽  
Xiaodong Huang ◽  
...  
Keyword(s):  
Active Layer ◽  
Yangtze River ◽  
Ground Deformation ◽  
Source Region ◽  
Deformation Monitoring ◽  
Tibet Plateau ◽  
Permafrost Degradation ◽  
The Yangtze River ◽  
Ground Ice

<p>Qinghai-Tibet Plateau (QTP) has the largest high-altitude permafrost zone in the middle and low latitudes. Substantial hydrologic changes have been observed in the Yangtze River source region and adjacent areas in the early 21st century. Permafrost on the QTP has undergone degradation under global warming. The ground leveling observation site near Tangula (33°04′N, 91°56′E) located in the degraded alpine meadow indicates that the ground has subsided 50mm since 2011. The contribution of permafrost degradation and loss of ground ice to the hydrologic changes is however still lacking. This study monitors the permafrost changes by applying the Small BAseline Subset InSAR (SBAS-InSAR) technique using C-band Sentinel-1 datasets during 2014-2019. The ground deformation over permafrost terrain is derived in spatial and temporal scale, which reflects the seasonal freeze-thaw cycle in the active layer and long-term thawing of ground ice beneath the active layer. Results show the seasonal thaw displacement exhibits a strong correlation with surficial geology contacts. The ground leveling data is used to validate the ground deformation monitoring results. Then, the ground deformation characteristics are analyzed against the landscape units. Last, the long-term inter-annual displacement value is used to estimate the water equivalent of ground ice melting.</p>

scholarly journals PIC v1.3: comprehensive R package for computing permafrost indices with daily weather observations and atmospheric forcing over the Qinghai–Tibet Plateau

2018 ◽  
Vol 11 (6) ◽  
pp. 2475-2491 ◽  
Author(s):  
Lihui Luo ◽  
Zhongqiong Zhang ◽  
Wei Ma ◽  
Shuhua Yi ◽  
Yanli Zhuang
Keyword(s):  
Ground Surface ◽  
R Package ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Trend Test ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Spatial Trends ◽  
The Impact ◽  
Qinghai Tibet Plateau

Abstract. An R package was developed for computing permafrost indices (PIC v1.3) that integrates meteorological observations, gridded meteorological datasets, soil databases, and field measurements to compute the factors or indices of permafrost and seasonal frozen soil. At present, 16 temperature- and depth-related indices are integrated into the PIC v1.3 R package to estimate the possible trends of frozen soil in the Qinghai–Tibet Plateau (QTP). These indices include the mean annual air temperature (MAAT), mean annual ground surface temperature (MAGST), mean annual ground temperature (MAGT), seasonal thawing–freezing n factor (nt∕nf), thawing–freezing degree-days for air and the ground surface (DDTa∕DDTs∕DDFa∕DDFs), temperature at the top of the permafrost (TTOP), active layer thickness (ALT), and maximum seasonal freeze depth. PIC v1.3 supports two computational modes, namely the stations and regional calculations that enable statistical analysis and intuitive visualization of the time series and spatial simulations. Datasets of 52 weather stations and a central region of the QTP were prepared and simulated to evaluate the temporal–spatial trends of permafrost with the climate. More than 10 statistical methods and a sequential Mann–Kendall trend test were adopted to evaluate these indices in stations, and spatial methods were adopted to assess the spatial trends. Multiple visual methods were used to display the temporal and spatial variability of the stations and region. Simulation results show extensive permafrost degradation in the QTP, and the temporal–spatial trends of the permafrost conditions in the QTP are close to those of previous studies. The transparency and repeatability of the PIC v1.3 package and its data can be used and extended to assess the impact of climate change on permafrost.

scholarly journals The Impact of Permafrost Degradation on Lake Changes in the Endorheic Basin on the Qinghai–Tibet Plateau

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1287
Author(s):  
Wenhui Liu ◽  
Changwei Xie ◽  
Wu Wang ◽  
Guiqian Yang ◽  
Yuxin Zhang ◽  
...  
Keyword(s):  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Ground Ice ◽  
Landsat Images ◽  
Temporal Area ◽  
Discontinuous Permafrost ◽  
Continuous Permafrost ◽  
Endorheic Basin ◽  
Ice Content ◽  
The Impact

Lakes on the Qinghai–Tibetan Plateau (QTP) have experienced significant changes, especially the prevailing lake expansion since 2000 in the endorheic basin. The influence of permafrost thawing on lake expansion is significant but rarely considered in previous studies. In this study, based on Landsat images and permafrost field data, the spatial-temporal area changes of lakes of more than 5 km2 in the endorheic basin on the QTP during 2000–2017 is examined and the impact of permafrost degradation on lake expansion is discussed. The main results are that permafrost characteristics and its degradation trend have close relationships with lake changes. Lake expansion in the endorheic basin showed a southwest–northeast transition from shrinking to stable to rapidly expanding, which corresponded well with the permafrost distribution from island-discontinuous to seasonally frozen ground to continuous permafrost. A dramatic lake expansion in continuous permafrost showed significant spatial differences; lakes expanded significantly in northern and eastern continuous permafrost with a higher ground ice content but slightly in southern continuous permafrost with a lower ground ice content. This spatial pattern was mainly attributed to the melting of ground ice in shallow permafrost associated with accelerating permafrost degradation. Whereas, some lakes in the southern zones of island-discontinuous permafrost were shrinking, which was mainly because the extended taliks arising from the intensified permafrost degradation have facilitated surface water and suprapermafrost groundwater discharge to subpermafrost groundwater and thereby drained the lakes. Based on observation and simulated data, the melting of ground ice at shallow depths below the permafrost table accounted for 21.2% of the increase in lake volume from 2000 to 2016.

scholarly journals Evaluating the Impact of Indoor Insulation on Historic Build-Ings: A Multilevel Approach Involving Heat and Moisture Simulations

2021 ◽  
Vol 11 (17) ◽  
pp. 7944
Author(s):  
Ivana Mattea Lisitano ◽  
Deborah Laggiard ◽  
Stefano Fantucci ◽  
Valentina Serra ◽  
Elisa Fenoglio
Keyword(s):  
Energy Savings ◽  
Moisture Transfer ◽  
Thermal Inertia ◽  
Building Envelope ◽  
Indoor Climate ◽  
Internal Wall ◽  
Winter Climate ◽  
Climate Conditions ◽  
Heat And Moisture ◽  
The Impact

The energy refurbishment of historic buildings is a complex task for building envelope designers who need to carefully consider building conservation guidelines and principles. In most cases, external wall insulation techniques can determine an unacceptable alteration of the historical value of a building. For this reason, internal wall insulation techniques have been used widely in the last few decades. Nevertheless, dealing with internal wall insulation requires a complex design to avoid the risk of condensation and moisture-related pathologies. Moreover, an internal wall insulation may have a relevant impact on indoor comfort conditions. In this paper, the Monastery of Santa Maria de Monfero in Galicia (Spain) has been adopted as a building case study to compare different technological solutions based on: (i) an insulating plaster layer, (ii) dry counter wall systems. In the first step, heat and moisture transfer simulations of the wall components were performed to analyze the hygrothermal behavior of the different alternatives considering two different climate conditions. In a second step, a simulation of the whole building was performed to analyze the impact of the retrofitting strategies on the indoor climate and on the building heating and cooling demand. The obtained results show that the counter wall solution leads to higher energy savings during the heating season in the colder winter climate. However, the use of insulating thermal plaster could also be a viable solution since they lead to several advantages in summer because of their higher thermal inertia. Therefore, the selection of the most appropriate insulation technique has to be evaluated carefully considering the outdoor/indoor climate and using a case-by-case approach.

The changing landscape of Canada's western boreal forest: the current dynamics of permafrost

2000 ◽  
Vol 30 (2) ◽  
pp. 283-287 ◽  
Author(s):  
Dale H Vitt ◽  
Linda A Halsey ◽  
Stephen C Zoltai
Keyword(s):  
Organic Matter ◽  
Little Ice Age ◽  
Water Levels ◽  
Ice Age ◽  
Ecosystem Change ◽  
Western Canada ◽  
Permafrost Degradation ◽  
Organic Matter Accumulation ◽  
The Impact

This paper examines the impact that climatic change over the last millennium has had on aggradation and degradation of permafrost peatlands and the associated change in organic matter accumulation. Permafrost reached its southernmost Holocene extent in boreal continental western Canada during the Little Ice Age with 28 800 km2 of permafrost peatland present within a sensitive zone demarcated by permafrost degradation. Subsequent degradation of permafrost has occurred in response to warming, with forested bogs changing to nonforested poor fens, associated with rising water levels. In conjunction with this ecosystem change, long-term net organic matter accumulation increases. As permafrost is in disequilibrium with climate, much of the permafrost that remains is in a relict state. Mapping of past and present permafrost distribution from peatland landforms indicates only 9% has degraded since the Little Ice Age, resulting in a 5% increase in long-term net organic matter accumulation. Of the permafrost that remains, 22% is in disequilibrium, located largely in the northern part of the sensitive zone. Additional loss of forested lands will occur in the future in boreal continental western Canada under present-day climatic conditions as permafrost approaches equilibrium, with a further 11% increase in long-term net organic matter accumulation predicted.

scholarly journals Role of rainwater induced subsurface flow in water-level dynamics and thermoerosion of shallow thermokarst ponds on the Northeastern Qinghai–Tibet Plateau

2014 ◽  
Vol 8 (6) ◽  
pp. 6117-6146 ◽  
Author(s):  
X. Pan ◽  
Q. Yu ◽  
Y. You
Keyword(s):  
Water Level ◽  
Active Layer ◽  
Water Budget ◽  
Pond Water ◽  
Ice Cover ◽  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Thermokarst Lakes ◽  
Thermal Regimes ◽  
Qinghai Tibet Plateau

Abstract. Understanding hydrological and thermal regimes of thermokarst lakes is of great importance for predicting their responses to climate change. However, mechanism of water-level dynamics and associated thermal effects on thermoerosion of thermokarst lakes are still not well understood on the Qinghai–Tibet Plateau (QTP). In this study, we investigate two typical shallow thermokarst ponds (namely small lakes) in a warm permafrost region with thick active layer on the northeastern QTP through quantifying water budget. Results demonstrate that, rainfall induced subsurface lateral flow dominates pond water-level regime. Annual variation of pond water-level relies on areal water budget of surrounding active layer, particularly the high variable of precipitation. Besides, it is worth noting the extraordinary warming during the late ice-cover period, because marked air gap between upper ice-cover and underlying water, led by the upward thawing of thick ice-cover, might result in greenhouse-like condition due to the unique weather that strong solar radiation and little snowpack. This hydrological mechanism also exerts evident impacts on thermal regime and thermoerosion of the shallow thermokarst ponds, and they are closely related to retreat of thermokarst pondshore and underlying permafrost degradation. These findings imply a localized model addressing the unique hydrological and thermal regimes of thermokarst lakes would be essential to study the evolution of these shallow rainwater dominated thermokarst ponds on the QTP.

scholarly journals PIC: Comprehensive R package for permafrost indices computing with daily weather observations and atmospheric forcing over the Qinghai–Tibet Plateau

2018 ◽  
Author(s):  
Lihui Luo ◽  
Zhongqiong Zhang ◽  
Wei Ma ◽  
Shuhua Yi ◽  
Yanli Zhuang
Keyword(s):  
Ground Surface ◽  
R Package ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Climate Simulation ◽  
Trend Test ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
The Impact ◽  
Qinghai Tibet Plateau

Abstract. An R package permafrost indices computing (PIC) was developed, which integrates meteorological observations, remote sensing data, and field measurements to compute the factors or indices of permafrost and seasonal frozen soil. At present, 16 temperature/depth-related indices are integrated into the R package PIC to estimate the possible change trends of frozen soil in the Qinghai–Tibet Plateau (QTP). These indices include the mean annual air temperature, mean annual ground surface temperature, mean annual ground temperature, seasonal thawing/freezing n factor (nt/nf), thawing/freezing degree-days of air and ground surface (DDTa/DDTs/DDFa/DDFs), temperature at the top of the permafrost, active layer thickness, and maximum seasonal freeze depth. The PIC package supports two computational modes, namely, the stations and region calculation that enables statistical analysis and intuitive visualization on the time series and spatial simulations. Over 10 statistical methods were adopted to evaluate these indices in stations, and a sequential Mann-Kendall trend test and spatial trend method were adopted. Multiple visual manners display the temporal and spatial variabilities on the stations and region. The data sets of 52 weather stations and a central region of QTP were prepared and simulated to evaluate the temporal–spatial change trends of permafrost with the climate. Simulation results show extensive permafrost degradation in QTP, and the temporal–spatial trends of the permafrost conditions in QTP were consistent with those of previous studies. The PIC package will serve engineering applications and can be used to assess the impact of climate change on permafrost.

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