青藏高原多年冻土活动层变化的数值模拟研究

The Qinghai-Tibet Plateau (QTP) contains the largest permafrost area in mid-latitude. Under climate warming, the degradation of permafrost and the increase of active-layer thickness have significant effects on constructions, hydrologic cycle, and ecological environment on the QTP. After years of development, land surface models have become an important tool for studying the changes in permafrost. However, the previous studies found that the land surface model’s soil parameterization was inaccurate for permafrost simulation and observation on the QTP was insufficient. Those two shortages limit the application of the land surface model over permafrost areas on the QTP. Based on the previous studies, this project will combine observations and simulations to overcome those shortages. By adding soil temperature and moisture probes in deep soil layer and sampling of undisturbed soils in permafrost sites, the heterogeneous properties of permafrost soil will be measured. By establishing a new soil parameterization scheme and simulating the soil thermal and hydrological dynamics in typical sites, the applicability of land surface model over permafrost area will be improved. Forcing by regional meteorological data, the distribution and variation of permafrost active-layer thickness will be simulated by improved model, and the response of permafrost degradation to climate change will be investigated. This study promises to improve the simulation accuracy of land surface model over permafrost area, and to provide scientific information for addressing the permafrost degradation under climate change.

青藏高原分布着中纬度地区面积最大的多年冻土。在变暖背景下，高原多年冻土退化，活动层深度加深，进而对高原工程建筑、水文和生态环境都产生重大影响。陆面模式的长足发展使其成为研究高原冻土变化的重要工具，前人研究发现，在青藏高原利用陆面模式进行冻土模拟存在土壤参数化不准确和观测数据缺乏两方面不足。这些不足限制了陆面模式在高原冻土区的模拟和应用。本项目拟在已有研究基础上，采用“站点观测—数值模拟”相结合的方法，加密观测深层土壤温湿度，采集分析冻土区原状土水热属性，获取多年冻土区垂直非均匀土壤水热特性；建立适合高原多年冻土模拟的参数化方案，模拟典型站点活动层深度和水热过程；最后利用改进后的陆面模式模拟高原冻土活动层分布和变化特征，研究多年冻土活动层对气候变化的响应。本研究有助于提高陆面模式在多年冻土区的适用性，为应对全球气候变化条件下高原冻土的退化提供科学支撑。

青藏高原分布着中纬度地区面积最大的多年冻土。在变暖背景下，高原多年冻土退化，活动层深度加深，进而对高原工程建筑、水文和生态环境都产生重大影响。陆面模式的长足发展使其成为研究高原冻土变化的重要工具，前人研究发现，在青藏高原利用陆面模式进行冻土模拟存在土壤参数化不准确和观测数据缺乏两方面不足。这些不足限制了陆面模式在高原冻土区的模拟和应用。本项目在已有研究基础上，采用“站点观测—数值模拟”相结合的方法，加密观测深层土壤温湿度，采集分析冻土区原状土水热属性，获取多年冻土区垂直非均匀土壤水热特性；建立适合高原多年冻土模拟的参数化方案，模拟典型站点活动层深度和水热过程；最后利用改进后的陆面模式模拟高原冻土活动层分布和变化特征，研究多年冻土活动层对气候变化的响应。通过本项目的实施，提高了陆面模式在多年冻土区的适用性，为预测和应对全球气候变化条件下高原冻土退化提供参考。另外我们获取了1979-2018年青藏高原活动层深度数据，为高原冻土工程实施和生态环境保护提供了数据支撑。