青藏高原地区因其海拔高、气温低，冻土和季节性冻土分布广泛。在全球变暖的背景下，青藏高原地区土壤温度升高，导致高原冻土退化严重。然而，青藏高原地区，尤其是广大的高原西部地区，土壤温度资料的匮乏，阻碍了人们对整个高原土壤冻融变化的准确认识。本项目拟利用Variable Infiltration Capacity (VIC）模型，借助敏感性分析和代理模型等技术手段，采用MODIS卫星地表温度资料进行模型参数标定，发展一套青藏高原地区时空分辨率较高（时间分辨率3小时，空间分辨率0.1度）、误差较小的土壤温度数据集。然后，将利用此数据集，分析青藏高原地区土壤“零温线”（土壤温度为0℃的等温线）的时空变化特征。本项目拟发展的青藏高原土壤温度数据集，将弥补现有的土壤温度数据集时空分辨率不足、误差较大的缺陷；同时，青藏高原地区土壤“零温线”的变化研究，有助于全面认识青藏高原地区土壤的冻融变化特征。

The Tibetan Plateau (TP) contains vast area of permafrost and seasonally frozen soil because of its high elevation and low surface air temperature. Permafrost on the TP has experienced noticeable degradation as the soil temperature rises in the context of global warming. However, due to the scarcity of soil temperature observation on the TP, especially in the western TP, the understanding of the changes of soil freezing-thawing processes lacks accuracy. The proposed study plans to use Variable Infiltration Capacity (VIC) model to generate a high spatiotemporal resolution and more accurate soil temperature dataset for the TP. MODIS land surface temperature will be used to calibrate the VIC model by sensitivity analysis and surrogate model methods. In addition, based on the dataset, the spatiotemporal variations of “zero isotherm (0℃ )” lines of soil temperature will be analyzed for the TP. This new soil temperature dataset will be of better quality in both resolution and accuracy compared to the existing lower spatiotemporal resolution and less accurate soil temperature dataset on the TP. Furthermore, the analysis of the changes of soil “zero isotherm” lines will help systematically understand the variations in soil freezing-thawing processes on the TP.