Page 25 - 《高原气象》2022年第1期

1 期 刘闻慧等：青藏高原土壤冻融过程关键参量时空分布特征分析 23

Characteristic Analysis of the Spatio-temporal Distribution of Key Variables

during the Soil Freeze-thaw Process over the Qinghai-Xizang Plateau

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LIU Wenhui ，WEN Jun ，CHEN Jinlei ，WANG Zuoliang ，LU Xuancheng ，WU Yueyue ，JIANG Yuqin 1
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（1. College of Atmospheric Sciences，Chengdu University of Information Technology/Sichuan Key Laboratory of Plateau Atmosphere
and Environment，Chengdu 610225，Sichuan，China；
2. State Key Laboratory of Cryosphere Sciences，Northwest Institute of Eco-Environment and Resources，Chinese Academy of
Sciences，Lanzhou 730000，Gansu，China；
3. Northwest Institute of Ecological Environment and Resources，Chinese Academy of Sciences/Key Laboratory of Land Surface
Process and Climate Change in the Cold and Arid Region of the Chinese Academy of Sciences，Lanzhou 730000，Gansu，China）
Abstract：The freeze-thaw process is one of the most prominent features of the land surface process on the Qing‐
hai-Xizang Plateau，and quantifying the variation of the key variables that denote the soil freeze-thaw process
has scientific significance for understanding the climate change，hydrological processes and ecosystems of the
Qinghai-Tibetan Plateau. By using the ECMWF/ERA5（European Centre for Medium-Range Weather Forecasts/
ERA5）reanalyzed soil temperature，volumetric soil water and air temperature data，the temporal and spatial
trends of the start date of soil freezing，the start date of soil thawing and the duration of the soil freezing and their
relationships with the air temperature and altitude were investigated by using linear regression，Mann-Kendall
test，moving t test and correlation analysis. These results demonstrated that the spatial distribution of soil freeze-
thaw process in the Qinghai-Xizang Plateau is characterized by a trend of delaying freeze，advancing thaw and
shortening freeze from the northwest to the southeast. The soil freeze-thaw process varied significantly on the
Qinghai-Xizang Plateau from 1979 to 2018. The start date of soil freezing was delayed by 14. 0 days with a rate
of 0. 17 d·a ，and the start date of soil thawing was advanced by 11. 0 days with a rate of 0. 07 d·a ，and the du‐
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ration of the soil freeze was shortened by 25. 0 days with a rate of 0. 23 d·a over the past 40 years. The overall
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trend of soil freeze-thaw process is the same in the Qinghai-Xizang Plateau，while the local rate is different.
Throughout the period of study，the duration of the soil freeze in the southern and the northern Changtang Pla‐
teau is shortened by 47. 2 days and 32. 9 days. The first date of the soil freeze，the first date of the soil thaw and
the duration of the soil freeze are significantly correlated with temperature and altitude. If the air temperature ris‐
es by 1. 0 ℃，the first date of the soil freeze will be delayed by 5. 2 days，and the first date of the soil thaw will
be advanced by 4. 5 days，so that the duration of the soil freeze will be shortened by 9. 8 days. In the high cold Ti‐
betan climatological zone，the first date of the soil freeze will be advanced by 9. 1 days，and the first date of the
soil thaw will be delayed by 4. 9 days，while the duration of the soil freeze will be increased by 13. 9 days as the
altitude increases by 1000. 0 m.
Key words：The Qinghai-Xizang Plateau；soil freeze-thaw process；land surface process；spatio-temporal distri‐
bution；climate change