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>

scholarly journals Freeze–Thaw Changes of Seasonally Frozen Ground on the Tibetan Plateau from 1960 to 2014

2020 ◽  
Vol 33 (21) ◽  
pp. 9427-9446
Author(s):  
Siqiong Luo ◽  
Jingyuan Wang ◽  
John W. Pomeroy ◽  
Shihua Lyu
Keyword(s):  
Tibetan Plateau ◽  
Regional Scale ◽  
The Tibetan Plateau ◽  
Hydrothermal Conditions ◽  
Frozen Ground ◽  
Important Indicator ◽  
Freeze Thaw ◽  
Start Date ◽  
Temperature And Precipitation ◽  
Geographical Factors

AbstractThe freeze–thaw changes of seasonally frozen ground (SFG) are 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. Freeze–thaw changes of SFG on a regional scale were assessed by multiple regression functions. Results showed multiyear mean maximum freeze depth, freeze–thaw duration, freeze start date, and thaw end date that 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. The freeze–thaw changes of SFG significantly affected by soil hydrothermal conditions on the TP 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 were larger than those averaged using meteorological station data because most stations are located at lower altitudes. Maximum freeze depth and freeze–thaw duration have decreased sharply since 2000 on the entire TP. Warming and wetting conditions of the soil resulted in a significant decrease in maximum freeze depth and freeze–thaw duration in the most area of the TP, while drying soil results in a slight increase of them in the southeast of the TP.

scholarly journals First Measurement of Soil Freeze/Thaw Cycles in the Tibetan Plateau Using CYGNSS GNSS-R Data

2020 ◽  
Vol 12 (15) ◽  
pp. 2361 ◽  
Author(s):  
Xuerui Wu ◽  
Zhounan Dong ◽  
Shuanggen Jin ◽  
Yang He ◽  
Yezhi Song ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Periodic Oscillation ◽  
Satellite System ◽  
Soil Freezing ◽  
The Tibetan Plateau ◽  
Freezing And Thawing ◽  
Current Application ◽  
Important Indicator ◽  
Freeze Thaw

The process of soil freezing and thawing refers to the alternating phase change of liquid water and solid water in the soil, accompanied by a large amount of latent heat exchange. It plays a vital role in the land water process and is an important indicator of climate change. The Tibetan Plateau in China is known as the “roof of the world”, and it is one of the most prominent physical characteristics is the freezing and thawing process of the soil. For the first time, this paper utilizes the spaceborne GNSS-R mission, i.e., CYGNSS (Cyclone Global Navigation Satellite System), to study the feasibility of monitoring the soil freeze-thaw (FT) cycles on the Tibetan Plateau. In the theoretical analysis part, model simulations show that there are abrupt changes in soil permittivities and surface reflectivities as the soil FT occurs. The CYGNSS reflectivities from January 2018 to January 2020 are compared with the SMAP FT state. The relationship between CYGNSS reflectivity and SMAP soil moisture within this time series is analyzed and compared. The results show that the effect of soil moisture on reflectivity is very small and can be ignored. The periodic oscillation change of CYGNSS reflectivity is almost the same as the changes in SMAP FT data. Freeze-thaw conversion is the main factor affecting CYGNSS reflectivity. The periodical change of CYGNSS reflectivity in the 2 years indicates that it is mainly caused by soil FT cycles. It is feasible to use CYGNSS to monitor the soil FT cycles in the Tibetan Plateau. This research expands the current application field of CYGNSS and opens a new chapter in the study of cryosphere using spaceborne GNSS-R with high spatial-temporal resolution.

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.

Diurnal freeze/thaw cycles of the ground surface on the Tibetan Plateau

2007 ◽  
Vol 52 (1) ◽  
pp. 136-139 ◽  
Author(s):  
MeiXue Yang ◽  
TanDong Yao ◽  
XiaoHua Gou ◽  
Nozomu Hirose ◽  
Hide Yuki Fujii ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Ground Surface ◽  
The Tibetan Plateau ◽  
Freeze Thaw

Sampling depth of L-band radiometer measurements of soil moisture and freeze-thaw dynamics on the Tibetan Plateau

2019 ◽  
Vol 226 ◽  
pp. 16-25 ◽  
Author(s):  
Donghai Zheng ◽  
Xin Li ◽  
Xin Wang ◽  
Zuoliang Wang ◽  
Jun Wen ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Sampling Depth ◽  
Freeze Thaw ◽  
L Band ◽  
Band Radiometer

scholarly journals Understanding precipitation recycling over the Tibetan Plateau using tracer analysis with WRF

2020 ◽  
Vol 55 (9-10) ◽  
pp. 2921-2937
Author(s):  
Yanhong Gao ◽  
Fei Chen ◽  
Gonzalo Miguez-Macho ◽  
Xia Li
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Precipitation Amount ◽  
Interaction Strength ◽  
Convective Precipitation ◽  
High Mountain ◽  
The Tibetan Plateau ◽  
Important Indicator ◽  
Precipitation Recycling ◽  
Atmosphere Interaction

Abstract The precipitation recycling (PR) ratio is an important indicator that quantifies the land-atmosphere interaction strength in the Earth system’s water cycle. To better understand how the heterogeneous land surface in the Tibetan Plateau (TP) contributes to precipitation, we used the water-vapor tracer (WVT) method coupled with the Weather Research and Forecasting (WRF) regional climate model. The goals were to quantify the PR ratio, in terms of annual mean, seasonal variability and diurnal cycle, and to address the relationships of the PR ratio with lake treatments and precipitation amount. Simulations showed that the PR ratio increases from 0.1 in winter to 0.4 in summer when averaged over the TP with the maxima centered at the headwaters of three major rivers (Yangtze, Yellow and Mekong). For the central TP, the highest PR ratio rose to over 0.8 in August, indicating that most of the precipitation was recycled via local evapotranspiration in summer. The larger daily mean and standard deviation of the PR ratio in summer suggested a stronger effect of land-atmosphere interactions on precipitation in summer than in winter. Despite the relatively small spatial extent of inland lakes, the treatment of lakes in WRF significantly impacted the calculation of the PR ratio over the TP, and correcting lake temperature substantially improved both precipitation and PR ratio simulations. There was no clear relationship between PR ratio and precipitation amount; however, a significant positive correlation between PR and convective precipitation was revealed. This study is beneficial for the understanding of land-atmosphere interaction over high mountain regions.

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.

scholarly journals The impacts of soil freeze/thaw dynamics on soil water transfer and spring phenology in the Tibetan Plateau

2018 ◽  
Vol 50 (1) ◽  
pp. e1439155 ◽  
Author(s):  
Huiru Jiang ◽  
Wenjiang Zhang ◽  
Yonghong Yi ◽  
Kun Yang ◽  
Guicai Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Soil Water ◽  
Water Transfer ◽  
The Tibetan Plateau ◽  
Spring Phenology ◽  
Freeze Thaw
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