scholarly journals Impact of frozen soil processes on soil thermal characteristics at seasonal to decadal scales over the Tibetan Plateau and North China

2021 ◽  
Vol 25 (4) ◽  
pp. 2089-2107
Author(s):  
Qian Li ◽  
Yongkang Xue ◽  
Ye Liu
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
North China ◽  
Thermal Characteristics ◽  
Cold Season ◽  
Frozen Soil ◽  
The Tibetan Plateau ◽  
Soil Processes ◽  
Frozen Ground ◽  
Freeze Thaw

Abstract. Frozen soil processes are of great importance in controlling surface water and energy balances during the cold season and in cold regions. Over recent decades, considerable frozen soil degradation and surface soil warming have been reported over the Tibetan Plateau and North China, but most land surface models have difficulty in capturing the freeze–thaw cycle, and few validations focus on the effects of frozen soil processes on soil thermal characteristics in these regions. This paper addresses these issues by introducing a physically more realistic and computationally more stable and efficient frozen soil module (FSM) into a land surface model – the third-generation Simplified Simple Biosphere Model (SSiB3-FSM). To overcome the difficulties in achieving stable numerical solutions for frozen soil, a new semi-implicit scheme and a physics-based freezing–thawing scheme were applied to solve the governing equations. The performance of this model as well as the effects of frozen soil process on the soil temperature profile and soil thermal characteristics were investigated over the Tibetan Plateau and North China using observation sites from the China Meteorological Administration and models from 1981 to 2005. Results show that the SSiB3 model with the FSM produces a more realistic soil temperature profile and its seasonal variation than that without FSM during the freezing and thawing periods. The freezing process in soil delays the winter cooling, while the thawing process delays the summer warming. The time lag and amplitude damping of temperature become more pronounced with increasing depth. These processes are well simulated in SSiB3-FSM. The freeze–thaw processes could increase the simulated phase lag days and land memory at different soil depths as well as the soil memory change with the soil thickness. Furthermore, compared with observations, SSiB3-FSM produces a realistic change in maximum frozen soil depth at decadal scales. This study shows that the soil thermal characteristics at seasonal to decadal scales over frozen ground can be greatly improved in SSiB3-FSM, and SSiB3-FSM can be used as an effective model for TP and NC simulation during cold season. Overall, this study could help understand the vertical soil thermal characteristics over the frozen ground and provide an important scientific basis for land–atmosphere interactions.

scholarly journals Impact of frozen soil processes on soil thermal characteristics at seasonal to decadal scales over the Tibetan Plateau and North China

2020 ◽  
Author(s):  
Qian Li ◽  
Yongkang Xue ◽  
Ye Liu
Keyword(s):  
Tibetan Plateau ◽  
Soil Temperature ◽  
Temperature Profile ◽  
Land Surface ◽  
North China ◽  
Thermal Characteristics ◽  
Frozen Soil ◽  
The Tibetan Plateau ◽  
Soil Processes ◽  
Freeze Thaw

Abstract. Frozen soil processes are of great importance in controlling surface water and energy balances during the cold season and in cold regions. Over recent decades, considerable frozen soil degradation and surface soil warming have been reported over the Tibetan Plateau and North China, but most land surface models have difficulty in capturing the freeze-thaw cycle and few validations focus on the effects of frozen soil processes on soil thermal characteristics in these regions. This paper addresses these issues by introducing a physically more realistic and computationally more stable and efficient frozen soil module (FSM) into a land surface model—the third-generation Simplified Simple Biosphere model (SSiB3-FSM). To overcome the difficulties in achieving stable numerical solutions for frozen soil, a new semi-implicit scheme and a physics-based freezing-thawing scheme were applied to solve the governing equations. The performance of this model, as well as the effects of frozen soil process on the soil temperature profile and soil thermal characteristics, were investigated over the Tibetan Plateau and North China using observation and models. Results show that the SSiB3 model with the FSM produces more realistic soil temperature profile and its seasonal variation than that without FSM during the freezing and thawing periods. The freezing process in soil delays the winter cooling, while the thawing process delays the summer warming. The time lag and amplitude damping of temperature become more pronounced with increasing depth. These processes are well simulated in SSiB3-FSM. The freeze-thaw processes could increase the simulated phase lag days and land memory at different soil depths, as well as the soil memory change with the soil thickness. Furthermore, compared with observations, SSiB3-FSM produces a realistic change of maximum frozen soil depth at decadal scales. This study shows the soil thermal characteristics at seasonal to decadal scales over frozen ground can be greatly improved in SSiB3-FSM and SSiB3-FSM can be used as an effective model for TP and NC simulation during cold reasons.

scholarly journals A new map of permafrost distribution on the Tibetan Plateau

2017 ◽  
Vol 11 (6) ◽  
pp. 2527-2542 ◽  
Author(s):  
Defu Zou ◽  
Lin Zhao ◽  
Yu Sheng ◽  
Ji Chen ◽  
Guojie Hu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Spatial Data ◽  
Land Surface ◽  
Future Research ◽  
Data Sets ◽  
The Tibetan Plateau ◽  
Freezing And Thawing ◽  
Frozen Ground ◽  
Distribution Maps ◽  
Spatial Data Sets

Abstract. The Tibetan Plateau (TP) has the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. Some permafrost distribution maps have been compiled but, due to limited data sources, ambiguous criteria, inadequate validation, and deficiency of high-quality spatial data sets, there is high uncertainty in the mapping of the permafrost distribution on the TP. We generated a new permafrost map based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated this map using various ground-based data sets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and soil properties (moisture content and bulk density). The temperature at the top of permafrost (TTOP) model was applied to simulate the permafrost distribution. Permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06  ×  106 km2 (0.97–1.15  ×  106 km2, 90 % confidence interval) (40 %), 1.46  ×  106 (56 %), and 0.03  ×  106 km2 (1 %), respectively, excluding glaciers and lakes. Ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) were used to validate the model. Validation results showed that the kappa coefficient varied from 0.38 to 0.78 with a mean of 0.57 for the five IRs and 0.62 to 0.74 with a mean of 0.68 within the three transects. Compared with earlier studies, the TTOP modelling results show greater accuracy. The results provide more detailed information on the permafrost distribution and basic data for use in future research on the Tibetan Plateau permafrost.

Spatial-Temporal Distribution and Change of Seasonally Frozen Ground on the Tibetan Plateau from 1960 to 2014

2020 ◽  
Author(s):  
Siqiong Luo
Keyword(s):  
Tibetan Plateau ◽  
Regional Scale ◽  
Temporal Distribution ◽  
Thermal Conditions ◽  
The Tibetan Plateau ◽  
Frozen Ground ◽  
Important Indicator ◽  
Freeze Thaw ◽  
Start Date ◽  
Geographical Factors

<p>The change in spatial-temporal distribution of seasonally frozen ground (SFG) is an important indicator of climate change. Based on observed daily freeze depth of SFG from meteorological stations on the Tibetan Plateau (TP) from 1960 to 2014, the spatial-temporal characteristics and  trends in SFG were analyzed, and the relationships between them and climatic and geographical factors were explored. Spatial-temporal distribution of SFG on a regional scale was assessed by multiple regression functions. Results showed multi-year mean maximum freeze depth, freeze-thaw duration, freeze start date, and thaw end date demonstrate obvious distribution characteristics of climatic zones. A decreasing trend in maximum freeze depth and freeze-thaw duration occurred on the TP from 1960 to 2014. The freeze start date has been later and the thaw end date has been significantly earlier. Warming and wetting conditions of the soil resulted in a decrease in the maximum freeze depth and freeze-thaw duration, both spatially and temporally. The spatial distribution of SFG has been altered significantly by soil thermal conditions on the TP and could be assessed by elevation and latitude or by air temperature and precipitation, due to their high correlations. The regional average of maximum freeze depth and freeze-thaw duration caused by climatic and geographical factors was larger than those averaged using meteorological station data because most stations are located at lower altitudes. Maximum freeze depth and freeze-thaw duration has decreased sharply since 2000 on the entire TP.</p>

Monitoring and Analysis of Fine-Grained Frozen Soil Temperature and Permafrost Table for Transmission Line Foundation

2012 ◽  
Vol 204-208 ◽  
pp. 694-698
Author(s):  
Shi Jun Ding ◽  
Yong Feng Cheng ◽  
Xian Long Lu ◽  
Yu Ping Yang
Keyword(s):  
Transmission Line ◽  
Cold Season ◽  
Frozen Soil ◽  
The Tibetan Plateau ◽  
Frozen Ground ◽  
Foundation Slab ◽  
Fine Grained ◽  
Permafrost Table ◽  
Thawing Depth ◽  
Frozen State

To analyze refreezing state and permafrost table of the frozen ground for the Qinghai-Tibet DC Transmission Line Engineering, temperature monitoring tests of fine-grained frozen soil were carried out and the thawing depth of backfilled soil was measured in Wudaoliang region of the Tibetan Plateau. The ground temperature fluctuates over time, and the fluctuation characteristics are determined by soil properties, climate, depth and other factors. The seasonally thawed layer is in the shallow of undisturbed frozen ground and backfilled soil. The maximum thawing depth of backfilled soil was about 2.3m more than permafrost table of the undisturbed frozen ground. Soil near the foundation slab was keeping frozen state. The results show that the construction of frozen ground in cold season is helpful to refreeze and keep frozen state of the ground, and can provide a basis for stability analysis of the engineering foundation.

scholarly journals Evaluation of Eight Current Reanalyses in Simulating Land Surface Temperature from 1979 to 2003 in China

2017 ◽  
Vol 30 (18) ◽  
pp. 7379-7398 ◽  
Author(s):  
Chunlüe Zhou ◽  
Kaicun Wang ◽  
Qian Ma
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
North China Plain ◽  
North China ◽  
Northwest China ◽  
Warming Trend ◽  
The Tibetan Plateau ◽  
Precipitation Frequency ◽  
The North ◽  
The North China Plain

Abstract Land surface temperature Ts provides essential supplementary information to surface air temperature, the most widely used metric in global warming studies. A lack of reliable observational Ts data makes assessing model simulations difficult. Here, the authors first examined the simulated Ts of eight current reanalyses based on homogenized Ts data collected at ~2200 weather stations from 1979 to 2003 in China. The results show that the reanalyses are skillful in simulating the interannual variance of Ts in China (r = 0.95) except over the Tibetan Plateau. ERA-Interim and MERRA land versions perform better in this respect than ERA-Interim and MERRA. Observations show that the interannual variance of Ts over the north China plain and south China is mostly influenced by surface incident solar radiation Rs, followed by precipitation frequency, whereas the opposite is true over the northwest China, northeast China, and the Tibetan Plateau. This variable relationship is well captured by ERA-Interim, ERA-Interim land, MERRA, and JRA-55. The homogenized Ts data show a warming of 0.34°C decade−1 from 1979 to 2003 in China, varying between 0.25° and 0.42°C decade−1 for the eight reanalyses. However, the reanalyses substantially underestimate the warming trend of Ts over northwest China, northeast China, and the Tibetan Plateau and significantly overestimate the warming trend of Ts over the north China plain and south China owing to their biases in simulating the Rs and precipitation frequency trends. This study provides a diagnostic method for examining the capability of current atmospheric/land reanalysis data in regional climate change studies.

scholarly journals A New Map of the Permafrost Distribution on the Tibetan Plateau

2016 ◽  
Author(s):  
Defu Zou ◽  
Lin Zhao ◽  
Yu Sheng ◽  
Ji Chen ◽  
Guojie Hu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Water Resource Management ◽  
Climate Modelling ◽  
The Tibetan Plateau ◽  
Freezing And Thawing ◽  
Frozen Ground ◽  
Data Set ◽  
Distribution Maps ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. The Tibetan Plateau (TP) possesses the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. A detailed database of the distribution and characteristics of permafrost is crucial for engineering planning, water resource management, ecosystem protection, climate modelling, and carbon cycle research. Although some permafrost distribution maps have been compiled in previous studies and have been proven to be very useful, due to the limited data source, ambiguous criteria, little validation, and the deficiency of high-quality spatial datasets, there is high uncertainty in the mapping of the permafrost distribution on the TP. In this paper, a new permafrost map was generated mostly based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated by various ground-based datasets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and in situ observed soil properties (moisture content and bulk density). The Temperature at the Top of Permafrost (TTOP) model was applied to simulate the permafrost distribution. The results show that permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06×106 km2 (40 %), 1.46×106 km2 (56 %), and 0.03×106 km2 (1 %), respectively, excluding glaciers and lakes. The ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) have been used to validate the model. The result of the validation shows that the kappa coefficient varies from 0.38 to 0.78 with an average of 0.57 at the five IRs and 0.62 to 0.74 with an average of 0.68 within the three transects. Compared with two maps compiled in 1996 and 2006 (kappa coefficients in average 0.06 and 0.35 in five IRs, 0.34 and 0.50 within three transects, respectively), the result of the TTOP modelling shows greater accuracy, especially in identifying thawing regions. Overall, the results provide much more detailed maps of the permafrost distribution and could be a promising basic data set for further research on permafrost on the Tibetan Plateau.

scholarly journals A Simulation and Validation of CLM during Freeze-Thaw on the Tibetan Plateau

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Xuewei Fang ◽  
Siqiong Luo ◽  
Shihua Lyu ◽  
Boli Chen ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Frozen Soil ◽  
Surface Radiation ◽  
The Tibetan Plateau ◽  
Hydraulic Property ◽  
Freeze Thaw ◽  
Community Land Model ◽  
Thaw Cycle ◽  
Soil Hydraulic Property ◽  
Soil Hydraulic

The applicability of a new soil hydraulic property of frozen soil scheme applied in Community Land Model 4.5 (CLM4.5), in conjunction with an impedance factor for the presence of soil ice, was validated through two offline numerical simulations conducted at Madoi (GS) and Zoige (ZS) on the Tibetan Plateau (TP). Sensitivity analysis was conducted via replacing the new soil hydraulic property scheme in CLM4.5 by the old one, using default CLM4.5 runs as reference. Results indicated that the new parameterization scheme ameliorated the surface dry biases at ZS but enlarged the wet biases which existed at GS site due to ignoring the gravel effect. The wetter surface condition in CLM4.5 also leads to a warmer surface soil temperature because of the greater heat capacity of liquid water. In addition, the combined impact of new soil hydraulic property schemes and the ice impedance function on the simulated soil moisture lead to the more reasonable simulation of the starting dates of freeze-thaw cycle, especially at the thawing stage. The improvements also lead to the more reasonable turbulent fluxes simulations. Meanwhile, the decreased snow cover fraction in CLM4.5 resulted in a lower albedo, which tended to increase net surface radiation compared to previous versions. Further optimizing is needed to take the gravel into account in the numerical description of thermal-hydrological interactions.

scholarly journals Soil-frost-enabled soil-moisture–precipitation feedback over northern high latitudes

2016 ◽  
Vol 7 (3) ◽  
pp. 611-625 ◽  
Author(s):  
Stefan Hagemann ◽  
Tanja Blome ◽  
Altug Ekici ◽  
Christian Beer
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Frozen Soil ◽  
The Arctic ◽  
Soil Processes ◽  
High Latitudes ◽  
Cold Region ◽  
Max Planck ◽  
Freezing And Thawing ◽  
Frozen Ground

Abstract. Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. The currently observed global warming is most pronounced in the Arctic region and is projected to persist during the coming decades due to anthropogenic CO2 input. This warming will certainly have effects on the ecosystems of the vast permafrost areas of the high northern latitudes. The quantification of such effects, however, is still an open question. This is partly due to the complexity of the system, including several feedback mechanisms between land and atmosphere. In this study we contribute to increasing our understanding of such land–atmosphere interactions using an Earth system model (ESM) which includes a representation of cold-region physical soil processes, especially the effects of freezing and thawing of soil water on thermal and hydrological states and processes. The coupled atmosphere–land models of the ESM of the Max Planck Institute for Meteorology, MPI-ESM, have been driven by prescribed observed SST and sea ice in an AMIP2-type setup with and without newly implemented cold-region soil processes. Results show a large improvement in the simulated discharge. On the one hand this is related to an improved snowmelt peak of runoff due to frozen soil in spring. On the other hand a subsequent reduction in soil moisture enables a positive feedback to precipitation over the high latitudes, which reduces the model's wet biases in precipitation and evapotranspiration during the summer. This is noteworthy as soil-moisture–atmosphere feedbacks have previously not been the focus of research on the high latitudes. These results point out the importance of high-latitude physical processes at the land surface for regional climate.

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