Thawing and freezing processes of active layer in Wudaoliang region of Tibetan Plateau  

作　　者：Lin Zhao Guodong Cheng Shuxun Li Xinmin Zhao Shaoling Wang 

机构地区：[1]Chinese Acad Sci, Inst Cold & Arid Reg Environm & Engn Res, State Key Lab Frozen Soil Engn, Lanzhou 730000, Peoples R China

出　　处：《Chinese Science Bulletin》2000年第23期2181-2187,共7页

摘　　要：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 theThe 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.

关 键 词：active LAYER FREEZING process water and HEAT couple. 

分 类 号：P642.14[天文地球—工程地质学]