江河源区土壤冻融循环时空变化特征分析

Characteristic Analysis of Temporal and Spatial Variations in Soil Freeze-Thaw Process in Sanjiangyuan Region

摘要: 了解土壤冻融循环的时空变化特征对于理解生态环境的气候变化响应具有重要意义。本文利用通用陆面过程模式(Common Land Model 5.0, CLM5.0)模拟的青藏高原土壤温度数据、气温数据，美国地球物理数据中心的海拔数据，首先验证CLM5.0模拟土壤温度数据在江河源区的适用性，然后使用线性趋势分析、相关分析等方法，分析1979年~2018年江河源区土壤冻融循环过程的三个关键参量，即土壤冻结开始时间、融化开始时间和冻结持续时间的时空变化特征，研究江河源区土壤冻融循环关键参量与年平均气温、海拔和纬度的关系，结果表明：1) 江河源区土壤冻融循环在空间分布上表现为自西北向东南，土壤冻结开始时间推迟，融化开始时间提前，冻结持续时间减少的特征。2) 江河源区近40年土壤冻结开始时间呈推迟趋势，融化开始时间呈提前趋势，冻结持续时间呈缩短趋势。3) 江河源区土壤冻融循环三个关键参量与气温和海拔均存在显著相关性。4) 近地表冻结持续时间缩短趋势随海拔高度的增加先增加后减小，与纬度先增加再减小再增加然后趋向稳定。

Abstract: Understanding the spatiotemporal variations of soil freeze-thaw cycles is crucial for comprehending the ecological and environmental responses to climate change. This study utilizes soil temperature data simulated by the Common Land Model (CLM5.0) over the Tibetan Plateau, air temperature data, and elevation data from the US National Geophysical Data Center. First, the applicability of the CLM5.0 simulated soil temperature data in the source region of the Yangtze and Yellow Rivers was validated. Then, using linear trend analysis and correlation analysis, the spatiotemporal variations of three key parameters of the soil freeze-thaw cycle process—freeze onset, thaw onset, and freeze duration—were analyzed for the period 1979~2018. The relationships between these key parameters and annual mean temperature, elevation, and latitude were also studied. The results indicate: 1) Spatially, the soil freeze-thaw cycle in the Sanjiangyuan Region shows a pattern from northwest to southeast, characterized by delayed freeze onset, earlier thaw onset, and reduced freeze duration. 2) Over the past forty years, the freeze onset time in the source region has been delayed, thaw onset time has advanced, and freeze duration has shortened. 3) There are significant correlations between the three key parameters and both temperature and elevation. 4) The shortening trend of near-surface freeze duration first increases and then decreases with increasing elevation, and first increases, then decreases, and finally stabilizes with latitude.