青藏高原季节冻土区和多年冻土区地表能量收支和蒸散发时间变化特征及影响因素对比研究

The comparison research work about the surface energy budget and evapotranspiration between regions of seasonally frozen ground and permafrost on the Tibetan Plateau are very important for the land surface process and ecological environment research works. This work is supported by the Nagqu Station of Plateau Climate and Environment under the Chinese Academy of Science. The observation fields include Nagqu BJ, Anduo, Kekexili NewD66 and Tanggula D105 sites. Thereinto, Nagqu BJ and Anduo sites located in the seasonally frozen ground regions on the Tibetan Plateau. Kekexili NewD66 and Tanggula D105 sites located in the permafrost regions on the Tibetan Plateau. The measurements include the eddy covariance systems, gradient meteorology towers and soil water-heat observation systems and the study time is from 2007 to 2016. Temporal (Interannual and annual and diurnal) variations and differences of the surface energy budget and evapotranspiration between regions of seasonally frozen ground and permafrost on the Tibetan Plateau at the four sites will be compared. Influencing factors of energy closure ratio will be discussed. Under the background of climate warming, influencing factors of variations of the energy budget and evapotranspiration between regions of seasonally frozen ground and permafrost on the Tibetan Plateau at the four sites will be analyzed, focused on the soil freezing and thawing processes and monsoon. This work hope deepen the understanding for physical processes and feedback mechanisms of frozen soil-atmosphere interaction, and do some references to the further research of energy-water cycle and to the improvement and development of frozen soil model on the Tibetan Plateau.

青藏高原季节冻土区与多年冻土区地表能量收支和蒸散发对比研究对高原的陆面过程研究及生态环境研究均有重要的意义。本项目依托中国科学院那曲高寒气候环境观测研究站，以那曲BJ站和安多站为高原季节冻土区的代表，以可可西里NewD66站和唐古拉D105站为高原多年冻土区的代表，利用涡动观测系统、梯度气象塔站及土壤水热观测系统等获取的长期连续的监测资料，以2007-2016年为研究时段，主要对比研究高原季节冻土区和多年冻土区地表能量收支和蒸散发的多尺度时间（年际/年内/日内）变化特征，探讨影响地表能量闭合率的因素；分析在气候变暖背景下，影响高原季节冻土区和多年冻土区地表能量收支和蒸散发变化的因素，重点对比研究土壤冻融过程和季风对两种冻土区地表能量收支过程和蒸散发变化的影响差异。希望加深对高原冻土-大气间相互作用的物理过程与反馈机制的理解，为高原今后进一步的能水循环研究和冻土模型改进和发展提供一定的参考。

季节冻土和多年冻土拥有不同的水热特性和物理过程，对比研究季节冻土区与多年冻土区的能水收支过程对陆面过程研究具有重要意义，同时对青藏高原地区经济建设和生态环境研究具有重要参考价值。为此，本项目依托中国科学院那曲高寒气候环境观测研究站，以那曲BJ站和安多站为青藏高原季节冻土区的代表，以可可西里NewD66站和唐古拉站为青藏高原多年冻土区的代表，利用各研究站点长期连续观测的涡动观测系统、梯度气象塔站和土壤水热监测系统，计算整理获取了较长时间序列的地表能量通量和蒸散发数据，并分析了地表能量闭合率。在此基础上，首先对青藏高原季节冻土区和多年冻土区的小气候特征进行了对比分析；其次改进得到了一种新的适用于青藏高原季节冻土区和多年冻土区的地表土壤热通量遥感参数化方案；然后将涡动相关法和总体输送法相结合，获得了精度更高的总体输送系数；由此对青藏高原季节冻土区和多年冻土区地表能量通量和蒸散发多时间尺度（日/季节/年际）变化特征进行了分析，研究了土壤冻融过程、积雪和季风等影响因子的影响，探讨了各因素的影响机理。希望加深对青藏高原冻土-大气间相互作用的物理过程与反馈机制的理解，为青藏高原能量和水分循环研究提供一定的参考。