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利用国家重大科学研究计划项目“青藏高原沙漠化对全球变化的响应”北麓河站2014-2015年陆面过程观测资料,根据5 cm土壤日最高和最低温度将冻土分为融化过程、完全融化、冻结过程和完全冻结四个阶段,分析了地表感热通量Hs、潜热通量LE、地表土壤热通量G_0和波文比在不同冻融阶段的季节和日变化特征,并探讨了土壤冻融过程对地表能量及其分配的影响。结果表明,波文比和G_0的季节变化受土壤冻融阶段转变的影响显著,其中土壤完全融化使波文比减小,G_0变为正值;土壤冻结使波文比增大,G_0变为负值。冻结过程对Hs和LE变化趋势的影响不明显,但是使波文比显著增大;融化过程使Hs停止增长并出现减小趋势,使LE增大,从而使波文比显著减小。Hs的日变化在不同冻融阶段差异较小。LE的日变化主要与浅层土壤含水量的大小和日变化有关,其中完全融化和完全冻结阶段土壤含水量的日变化较小,土壤含水量越大,LE越大;在融化过程和冻结过程阶段,土壤含水量的日变化较大,且与R_(net)的日变化相反,限制了LE的增长。在冻结过程阶段,受冻融过程的影响,G_0的日变化小于其他阶段。
Based on the observation data of Beiluhe Station from 2014 to 2015, the permafrost is divided into melting process according to the maximum and minimum temperature of 5 cm soil daily, using the project of National Significant Scientific Research Plan “Response of desertification of the Tibetan Plateau to global change” Completely melted, frozen and completely frozen. The seasonal and diurnal variation characteristics of surface sensible heat flux Hs, latent heat flux LE, surface soil heat flux G_0 and Bowen ratio in different freezing and thawing periods were analyzed and discussed Effect of soil freezing and thawing process on surface energy and its distribution. The results show that the seasonal variations of Bowen’s ratio and G_0 are significantly affected by the transition of the soil during the freeze-thaw period, in which the complete thawing of the soil reduces the wave ratio and G_0 becomes positive. The soil freezing increases the wave ratio and G_0 becomes Negative. The effect of freezing process on the trend of Hs and LE was not obvious, but the wave ratio was significantly increased. The melting process led to the increase of Hs and the decrease of Hs, resulting in a significant reduction of the Bowen ratio. The diurnal variation of Hs has little difference in different freeze-thaw phases. The diurnal variation of LE was mainly related to the size and diurnal variation of soil water content. The diurnal variation of soil water content was less in the stage of complete thawing and complete freezing. The larger the soil moisture content was, the larger the LE was. During the thawing and freezing processes At the same time, the diurnal variation of soil water content is larger, and contrary to the daily change of R net, the growth of LE is limited. In the process of freezing, influenced by the process of freezing and thawing, the daily variation of G_0 is less than that of other stages.