北半球多年冻土区活动层厚度历史分布及未来预测（1850-2100）

多年冻土区的季节融化层，即活动层，是季节冻土研究中重要组成部分，其变化也深受气候变化的影响。活动层厚度变化深刻影响地~气之间能量传递、水分循环、碳循环、以及地表和地下水文过程、和植被生长。作者通过收集北半球347个站点的长时间序列活动层厚度，同时几十个CMIP5输出的气温资料，通过Stefan方程，构建北半球多年冻土区E-factor；最后耦合融化指数获取了北半球多年冻土区活动层厚度的空间分布及不同气候情景下的未来预测。经检验发现，观测值与模拟值具有显著的相关性，相关系数R=0.84（P<0.01），平均百分比误差为4.7%，平均偏离误差为-11.7 cm，均方根误差为64 cm。该数据产品可以用于冻土与气候变化、冻土碳循环、冻土生态水文过程、冻土工程等相关研究。

The seasonal thaw layer in permafrost regions, also known as the active layer, is a critical component of seasonal frozen soil research, and its dynamics are strongly impacted by climate change. Changes in active layer thickness profoundly affect surface-atmosphere energy transfer, water cycle, carbon cycle, surface and subsurface hydrological processes, as well as vegetation growth. The authors collected long-term time-series active layer thickness data from 347 sites across the Northern Hemisphere, along with dozens of CMIP5-derived air temperature datasets, developed the E-factor for Northern Hemisphere permafrost regions using the Stefan equation, and finally coupled with the thaw index to derive the spatial distribution of active layer thickness in Northern Hemisphere permafrost regions and future projections under different climate scenarios. Validation results showed a significant correlation between observed and simulated values, with a correlation coefficient R=0.84 (P<0.01), a mean percentage error of 4.7%, a mean deviation error of -11.7 cm, and a root mean square error of 64 cm. This data product can be applied to relevant studies on permafrost and climate change, permafrost carbon cycle, permafrost eco-hydrological processes, permafrost engineering, and other related research fields.