青藏高原腹地活动层导热率分布格局及区域差异研究

Soil thermal conductivity (STC) within the active layer in permafrost is one of the key parameters for the land surface processes in cold region. It is also an important conponent to predict the global climate change. Existed works indicated that the single scheme for thermal condcutivity is difficult to cover the whole soil types, porosoty and saturation. As a result, the parameterizing schemes for STC in the climate model and professional criterions mostly yield an overestimated value during the frozen state in the Qinghai-Tibet Plateau (QTP). Consequently, a great deal of uncertainty was introduced in the temperature and moisture simulation in the QTP. At the same time, it also greatly limits the nedds in egineering constructions. Thus for the QTP, the basic data and appropriate parameterization scheme in STC are the key to solve such problem. Based on our existing works, the project is proposed to get the based bata in STC by the means of the observation in gradient of STC, thermal and moisture content within active layer on the typical land surface in the QTP. And then, the distributin pattern in STC will be analized during freeze-thaw cycle. After that, the variation mechnism and regional differences in STC is be investigated. Finally, in combination with other soil physical data, the parameterization group to satisfy the different regional regime can be developed. The implement of this project will help to further investigate the distribution pattern and regional differences in STC, and provide the basic parameter for the climate simulationand engineering design in cold region.

多年冻土区活动层土壤导热率是研究寒区地表过程的关键参数之一，也是全球变化预测的重要组分。研究表明，目前单一导热率参数方案难以涵盖所有的土壤类型、孔隙度及饱和度。受此影响，模式及国内规范的方案大都高估了青藏高原地区冻结期间的导热率。这给青藏高原地区陆面温度及水分模拟引入了极大的不确定性，同时也极大的限制工程建设的需要。而青藏高原导热率的基础数据及合适的参数化方案是解决问题的关键。本项目拟在已有研究的基础上，通过青藏高原多年冻土区典型下垫面活动层导热率梯度及水热梯度的过程监测，得到导热率基础数据，在此基础上分析研究导热率的分布格局，研究冻融过程中导热率变化机制及区域差异特点，结合其它土壤物理参数，最终形成可以满足不同区域特点的导热率参数化方案组。本项目的实施，将有助于更进一步摸清该地区土壤导热率分布格局及区域差异特征，为气候模拟、寒区工程设计提供基础参数。

多年冻土区活动层土壤导热率是研究寒区地表过程的关键参数之一，也是全球变化预测的重要组分。目前单一导热率参数方案难以涵盖所有的土壤类型、孔隙度及饱和度，适用于不同冻土类型的参数化方案组合是解决问题的关键，而青藏高原地区导热率基础数据获取、导热率分布格局、时空差异特征研究及对活动层水热运移特征是研究的基础。针对青藏高原复杂的下垫面类型及土壤复杂多变的特点，优化现有的方案，形成适用于青藏高原地表导热率方案组。研究结果为较准确预估青藏高原大幅增暖引起的气候、生态、水文、工程等资源环境效应研究提供基础参数。. 通过项目实施，积累了较长序列的监测数据，在观测资料及样品实验分析的基础上，较系统的分析了活动层冻融过程中导热率的动态变化特点，研究区域导热率冻结期小，非冻结期大；冻结初始含水量低于某一临界值是导致活动层表层导热率冻结期小而非冻结期大的主要原因；研究区区域这一临界含水量为0.195 m3m-3；同时青藏高原区域导热率随土壤容重的增大而增大，随下垫面植被盖度的增大而减小，高寒草甸土的土壤导热率小于高寒草原土的导热率；集成前期的研究结果，结合后续的原位观测，优化了导热率参数化方案，得到了适用于青藏高原不同区导热率参数化方案组，独立检验结果显示，方案在青藏高原计算误差较小，可用于青藏高原地区不同区域导热率的计算。