Thawing and freezing processes of active layer in Wudaoliang region of Tibetan Plateau
Thawing and freezing processes of active layer in Wudaoliang region of Tibetan Plateau
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DOI：
10.1007/bf02886326
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发表时间：
2000-12
影响因子：
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通讯作者：
Lin Zhao;G. Cheng;Shuxun Li;Xinmin Zhao;Shao-yong Wang
中科院分区：
文献类型：
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作者：
Lin Zhao;G. Cheng;Shuxun Li;Xinmin Zhao;Shao-yong Wang
冻土与大气的相互作用是通过覆盖层活动层的热、湿传递来完成的。因此，研究冻土解冻和冻结过程中活动层的热力和水动力学是揭示冻土与大气热湿交换的关键。e.夏季解冻阶段（ST）、秋季冻结阶段（AF）、冬季降温阶段（WC）、春季升温阶段（SW）。热水耦合流动在ST和AF阶段更为复杂，在这两个阶段有更多的水迁移。在其他两个阶段，热量主要通过传导热流传递，水迁移较少。在解冻和冻结阶段，研究了重力驱动的水分入渗过程、温度梯度和渗透梯度驱动的水分平流和蒸馏水过程、毛细作用驱动的水分迁移过程和温度梯度驱动的未冻水迁移过程。冻土层附近含水率在经过一次融冻循环后趋于增加，这是冻土层附近地表厚冰层形成的主要原因。
The interaction between permafrost and atmosphere is accomplished through transfer of heat and moisture in the overlay active layer. Thus, the research on the thermal and hydrodynamics of active layer during the thawing and freezing processes was considered a key to revealing the heat and moisture exchanges between permafrost and atmosphere. The monitoring and research on active layer were conducted because permafrost occupies about two thirds of the total area of the Tibetan Plateau. Based on the analysis of the ground temperature data and soil moisture data of monitoring near the Wudaoliang region of the Tibetan Plateau, the thawing and freezing processes of active layer were divided into four stages, i.e. summer thawing stage (ST), autumn freezing stage (AF), winter cooling stage (WC) and spring warming stage (SW). Coupled heat and water flow is much more complicated in ST and AF, and more amount of water is migrating in these two stages. Heat is transferred mainly via conductive heat flow in the other two stages, and less water migrated. Four water migration and coupled heat flow processes were addressed for the thawing and freezing stages, which are water infiltration driven by gravity, moisture advection and distillation driven by temperature and osmotic gradients, water migration driven by capillarity and unfrozen water migration driven by temperature gradient. The water content near the permafrost table tends to increase after one thawing and freezing cycle, which is the main reason for the development of thick ground ice layer near permafrost table.