Analysis of Spatiotemporal Variations of Freeze-thaw State of Surface Soil in Hexi Corridor in Recent 40 Years
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    Abstract:

    In order to explore the law of soil freeze-thaw in Hexi Corridor, based on the hourly surface temperature data of ERA5-LAND, the changes of surface soil freeze-thaw state in the past 40 years were analyzed by dividing different freeze-thaw stages and combining Mann-Kendall trend test and linear regression method. The results showed that: (1) The number of occurrence days in the spring transition period were more in plains than in mountainous areas, and the average annual occurrence days were more than 65 days. The number of occurrence days of complete melting period was more in the north than in the south, more in the east than in the west at the same latitude, and the number of occurrence days in more than 200 days was increasing. The number of average annual occurrence days in the autumn transition period was the least, about 50 days, and the number of days of complete freezing increased with the increase of altitude, among which the spatial distribution of the number of days in the spring transition period changed significantly with time. (2) The start date of the spring transition period and the complete melting period was gradually postponed from north to south, and the maximum difference between the north and the south was more than 90 days, and the spatial distribution of the start date of the complete melting period in different periods changed significantly. The start date of the autumn transition period was the opposite of the former, gradually advancing from north to south, and there was no obvious difference in spatial distribution between different periods. Most areas were completely frozen in December, and high-altitude mountainous areas were fully frozen in November. (3) The start date of the spring transition period was lagging behind in most areas of the study area, and the start date of the complete melting period was advanced, so the number of days of the spring transition period decreased at a rate of 0.2 d/a, while the start date of the autumn transition period in most areas was lagging, resulting in the increase of the number of days of complete melting period at a rate of 0.3 d/a. The number of days of complete freezing period in the northern part of the study area increased, while the southern Qilian Mountains showed a decreasing trend, and the start date of the complete freezing period was generally delayed at a rate of 0.03 d/a. (4) The number of days of complete melting in mountainous areas, oases and desert areas in the past 40 years increased at the rates of 0.393, 0.321 and 0.288 d/a, the start date was advanced by 0.134, 0.188 and 0.206 d/a, the number of days of complete freezing period decreased by 0.353, 0.219, and 0.016 d/a, respectively, and the start date was delayed at the rate of 0.06, 0.1, 0.01 d/a. Under the trend of global warming, for every 1°C increase in annual average temperature, the number of days of complete melting increased by 8.1 days, the start date was advanced by 4.53 days, the number of days of complete freezing period decreased by 9.02 days, and the start date was delayed by 3.27 days. The results can provide a theoretical basis for the study of soil freeze-thaw response to climate change.

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History
  • Received:April 11,2023
  • Revised:
  • Adopted:
  • Online: December 27,2023
  • Published: December 28,2023