scholarly journals Analysis on the Temporal and Spatial Characteristics of the Shallow Soil Temperature of the Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Yujie Li ◽  
Cunjie Zhang ◽  
Zhenchao Li ◽  
Liwei Yang ◽  
Xiao Jin ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Observational Data ◽  
Temperature Increase ◽  
Soil Layer ◽  
Tibet Plateau ◽  
Shallow Soil ◽  
Increasing Trend ◽  
Temporal And Spatial ◽  
Region 10 ◽  
Qinghai Tibet Plateau

Abstract Shallow soil refers to the soil layer within 50 cm underground. Shallow soil temperature (ST) affects many processes that occur in the soil. Therefore, the study of shallow ST is of great significance in understanding energy, hydrological cycles and climate change. This work collected the observational data from 141 meteorological stations on the Qinghai-Tibet Plateau from 1981 to 2020, analyzed the ST as well as its temporal and spatial change characteristics at different levels. The results show that: 1) The shallow ST has a gradually increasing trend from north to south, from west to east. From the perspective of time characteristics, the increasing trend is obvious. The temperature increase of 0–20 cm (the surface layer of the shallow soil) is roughly the same. The average annual is 9.15–9.57 ℃, the interdecadal variabilities are 0.49–0.53 K/10a. The average annual of 40 cm (the bottom layer) is 8.69 ℃, the interdecadal variability reaches by 0.98 K/10a; 2) Judging from the 12 regions of 20 cm, the temperature increase trend is obvious, but there are certain regional differences. The average value ranges from 4.3 ℃ (region 4, Qaidam Plateau) to 18.1 ℃ (region 10, Southeast Qinghai-Tibet Plateau), the difference is nearly 14 K. The standard deviation ranges from 0.38 K (region 10) to 0.82 K (region 11, Northern Qiangtang Plateau); 3) The results of the reanalysis data are lower than the observational data. This work is significant for understanding the characteristics of the ST evolution and the land-atmosphere interaction on the Qinghai-Tibet Plateau.

scholarly journals Impacts of climate and reclamation on temporal variations in CH<sub>4</sub> emissions from different wetlands in China: from 1950 to 2010

2015 ◽  
Vol 12 (23) ◽  
pp. 6853-6868 ◽  
Author(s):  
T. Li ◽  
W. Zhang ◽  
Q. Zhang ◽  
Y. Lu ◽  
G. Wang ◽  
...  
Keyword(s):  
Climate Warming ◽  
Coastal Wetlands ◽  
Temporal Variations ◽  
Tibet Plateau ◽  
Atmospheric Methane ◽  
Temporal And Spatial Variations ◽  
Ch4 Emissions ◽  
Natural Wetlands ◽  
Temporal And Spatial ◽  
Qinghai Tibet Plateau

Abstract. Natural wetlands are among the most important sources of atmospheric methane and thus important for better understanding the long-term temporal variations in the atmospheric methane concentration. During the last 60 years, wetlands have experienced extensive conversion and impacts from climate warming which might result in complicated temporal and spatial variations in the changes of the wetland methane emissions. In this paper, we present a modeling framework, integrating CH4MODwetland, TOPMODEL, and TEM models, to analyze the temporal and spatial variations in CH4 emissions from natural wetlands (including inland marshes/swamps, coastal wetlands, lakes, and rivers) in China. Our analysis revealed a total increase of 25.5 %, averaging 0.52 g m−2 per decade, in the national CH4 fluxes from 1950 to 2010, which was mainly induced by climate warming. Larger CH4 flux increases occurred in northeastern, northern, and northwestern China, where there have been higher temperature rises. However, decreases in precipitation due to climate warming offset the increment of CH4 fluxes in these regions. The CH4 fluxes from the wetland on the Qinghai–Tibet Plateau exhibited the lowest CH4 increase (0.17 g m−2 per decade). Although climate warming has accelerated CH4 fluxes, the total amount of national CH4 emissions decreased by approximately 2.35 Tg (1.91–2.81 Tg), i.e., from 4.50 Tg in the early 1950s to 2.15 Tg in the late 2000s, due to the wetland loss totalling 17.0 million ha. Of this reduction, 0.26 Tg (0.24–0.28 Tg) was derived from lakes and rivers, 0.16 Tg (0.13–0.20 Tg) from coastal wetlands, and 1.92 Tg (1.54–2.33 Tg) from inland wetlands. Spatially, northeastern China contributed the most to the total reduction, with a loss of 1.68 Tg. The wetland CH4 emissions reduced by more than half in most regions in China except for the Qinghai–Tibet Plateau, where the CH4 decrease was only 23.3 %.

scholarly journals Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow of the Qinghai-Tibet Plateau, China

2009 ◽  
Vol 13 (3) ◽  
pp. 327-341 ◽  
Author(s):  
W. Genxu ◽  
H. Hongchang ◽  
L. Guangsheng ◽  
L. Na
Keyword(s):  
Heat Flux ◽  
Soil Temperature ◽  
Soil Water ◽  
Vegetation Cover ◽  
Alpine Meadow ◽  
Root Zone ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Qinghai Tibet Plateau

Abstract. Alpine meadow is one of the most widespread grassland types in the permafrost regions of the Qinghai-Tibet Plateau, and the transmission of coupled soil water heat is one of the most crucial processes influencing cyclic variations in the hydrology of frozen soil regions, especially under different vegetation covers. The present study assesses the impact of changes in vegetation cover on the coupling of soil water and heat in a permafrost region. Soil moisture (θv), soil temperature (Ts), soil heat content, and differences in θv−Ts coupling were monitored on a seasonal and daily basis under three different vegetation covers (30, 65, and 93%) on both thawed and frozen soils. Regression analysis of θv vs. Ts plots under different levels of vegetation cover indicates that soil freeze-thaw processes were significantly affected by the changes in vegetation cover. The decrease in vegetation cover of an alpine meadow reduced the difference between air temperature and ground temperature (ΔTa−s), and it also resulted in a decrease in Ts at which soil froze, and an increase in the temperature at which it thawed. This was reflected in a greater response of soil temperature to changes in air temperature (Ta). For ΔTa−s outside the range of −0.1 to 1.0°C, root zone soil-water temperatures showed a significant increase with increasing ΔTa−s; however, the magnitude of this relationship was dampened with increasing vegetation cover. At the time of maximum water content in the thawing season, the soil temperature decreased with increasing vegetation. Changes in vegetation cover also led to variations in θv−Ts coupling. With the increase in vegetation cover, the surface heat flux decreased. Soil heat storage at 20 cm in depth increased with increasing vegetation cover, and the heat flux that was downwardly transmitted decreased. The soil property varied greatly under different vegetation covers, causing the variation of heat conductivity and water-heat hold capacity in topsoil layer in different vegetation cover. The variation of heat budget and transmitting in soil is the main factor that causes changes in soil thawing and freezing processes, and θv−Ts coupling relationship under different vegetation fractions. In addition to providing insulation against soil warming, vegetation in alpine meadows within the permafrost region also would slow down the response of permafrost to climatic warming via the greater water-holding capacity of its root zone. Such vegetation may therefore play an important role in conserving water in alpine meadows and maintaining the stability of engineering works constructed within frozen soil of the Qinghai-Tibet Plateau.

Dynamic Behavior of Pile Foundation in Frozen and Thawing Soil

2011 ◽  
Vol 105-107 ◽  
pp. 1391-1399
Author(s):  
Hao Li ◽  
Wei Nan Lu
Keyword(s):  
Pile Foundation ◽  
Dynamic Stiffness ◽  
Soil Layer ◽  
Tibet Plateau ◽  
Triaxial Tests ◽  
Permafrost Region ◽  
Harmonic Load ◽  
Stiffness And Damping ◽  
Qinghai Tibet Plateau ◽  
Temperature Dynamic

Permafrost is widespread in China, especially in Northeast China and the Qinghai-Tibet Plateau. Regions like Qinghai-Tibet Plateau have the most strenuous crustal movement. Therefore, earthquake-resistance of structures in permafrost region is an important issue. Furthermore, the permafrost will degenerate gradually as global warming mounts up. In some regions permafrost thickness tends to attenuate. Most bridge designs adopt pile foundation in order to reduce the effects of instable frost. The deterioration of frost leads to degradation of anti-seismic performance of bridges’ pile foundations. Pile-soil dynamic interaction numerical analysis models are established based on data of indoor low-temperature dynamic triaxial tests. Studies are performed on the dynamic stiffness and damping characters and the influencing factors of pile foundation under vertical harmonic load in frozen and thawing soil. The result shows that the dynamic response of the pile decreases along the depth, and the frictional resistance around the pile mainly distributes along the upper half of the pile, and the dynamic stiffness and damping of the pile are affected by temperature. Dynamic stiffness increases as temperature goes down, whereas the decrease of the temperature of frozen soil can notably lower the dynamic damping of the head of the pile. As the frequency of the dynamic load augments, the dynamic stiffness of the head increases marginally, whereas frequency has little influence on damping. The relative thickness of the frozen and thawing soil layer has considerable influence on dynamic stiffness, but negligible on damping.

scholarly journals Assessing the simulated soil hydrothermal regime of the active layer from the Noah-MP land surface model (v1.1) in the permafrost regions of the Qinghai–Tibet Plateau

2021 ◽  
Vol 14 (3) ◽  
pp. 1753-1771
Author(s):  
Xiangfei Li ◽  
Tonghua Wu ◽  
Xiaodong Wu ◽  
Jie Chen ◽  
Xiaofan Zhu ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Snow Cover ◽  
Land Surface ◽  
Tibet Plateau ◽  
Cold Bias ◽  
Surface Model ◽  
Model Parameters ◽  
Hydrothermal Regime ◽  
Qinghai Tibet Plateau ◽  
Permafrost Regions

Abstract. Extensive and rigorous model intercomparison is of great importance before model application due to the uncertainties in current land surface models (LSMs). Without considering the uncertainties in forcing data and model parameters, this study designed an ensemble of 55 296 experiments to evaluate the Noah LSM with multi-parameterization (Noah-MP) for snow cover events (SCEs), soil temperature (ST) and soil liquid water (SLW) simulation, and investigated the sensitivity of parameterization schemes at a typical permafrost site on the Qinghai–Tibet Plateau (QTP). The results showed that Noah-MP systematically overestimates snow cover, which could be greatly resolved when adopting the sublimation from wind and a semi-implicit snow/soil temperature time scheme. As a result of the overestimated snow, Noah-MP generally underestimates ST, which is mostly influenced by the snow process. A systematic cold bias and large uncertainties in soil temperature remain after eliminating the effects of snow, particularly in the deep layers and during the cold season. The combination of roughness length for heat and under-canopy (below-canopy) aerodynamic resistance contributes to resolving the cold bias in soil temperature. In addition, Noah-MP generally underestimates top SLW. The runoff and groundwater (RUN) process dominates the SLW simulation in comparison to the very limited impacts of all other physical processes. The analysis of the model structural uncertainties and characteristics of each scheme would be constructive to a better understanding of the land surface processes in the permafrost regions of the QTP as well as to further model improvements towards soil hydrothermal regime modeling using LSMs.

scholarly journals Dynamics of lake area on the Qinghai-Tibet plateau from 2000 to 2015

2019 ◽  
Vol 2 ◽  
pp. 1-7 ◽  
Author(s):  
Xianghong Che ◽  
Min Feng ◽  
Jiping Liu ◽  
Yong Wang ◽  
Qing Sun
Keyword(s):  
Yellow River ◽  
Global Scale ◽  
Water Bodies ◽  
Tibet Plateau ◽  
Medium Size ◽  
Power Exponent ◽  
Lake Area ◽  
Water Detection ◽  
Increasing Trend ◽  
Qinghai Tibet Plateau

<p><strong>Abstract.</strong> The distribution of lakes in space and its change over time are closely related to many environmental and ecological issues, and are important factors that must be considered in human socio-economic development. In this paper, the water detection method is utilized to derive monthly water bodies, and then a seed set expansion approach was explored to extract lakes larger than 0.1&amp;thinsp;km<sup>2</sup>. Since lakes number and size can effectively reflect the distribution characteristics of water bodies, their change of the number, area and distribution are analyzed. The results shows there is a prominent power exponent relation between lake size and lake number for the Qinghai-Tibet plateau (QTP), which is similar to existing analysis of global scale. The number density of medium size of lakes on the QTP is higher than other types of lakes. The number of lakes displayed a decreasing trend from 2000 to 2015 with the <i>R</i><sup>2</sup> of 0.41. There was an increasing trend with an increasing rate of 356.86&amp;thinsp;km<sup>2</sup>/year (0.72%). Specifically, 46.54% of lakes area are increasing, and mostly distributed in Alpine grassland and shrub woodlands zone of the central Tibetan plateau. Shrinking lakes mostly with the area less than 10&amp;thinsp;km<sup>2</sup> are situated on the woodland and shrub and grass areas in south-eastern Tibet. Finally, the analysis of monthly lake area of four lakes at the source of the Yellow River demonstrates the lakes area of each month from June to September witness an increasing trend, and the largest increasing rate is on June, which has a strong seasonality.</p>

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