A study on soil thermodynamic characteristics of active layer in northern Tibetan Plateau
青藏高原北部活动层土壤热力特性的研究

Using the data of soil temperature gradient, soil moisture and soil heat flux observed from Oct. 2003 to Sep. 2004 at sites of Kekexili (QT01), Beiluhe (QT02), Kaixinling (QT05) and Tongtianhe (QT06), thermodynamics parameters such as soil thermal conductivity, volumetric heat capacity and thermal diffusivity are calculated. The results show that these parameters in northern Tibetan Plateau are different from those in Gobi and western Tibetan Plateau. In the four sites mentioned above, the thermal conductivities and diffusivities of QT02, QT05 and QT06 are larger in summer and autumn and smaller in winter while the variation trend of thermal capacities are opposite to the thermal conductivities and diffusivities; as for QT01 site, the thermal conductivity was larger in spring than in summer; the possible reason of small thermal conductivities under the frozen ground is the fine-grained and lower moisture content of topsoil; and under the condition of frozen ground, soil thermodynamics parameters could be written as a function of temperature, ice content and soil salinity while under the unfrozen ground the soil moisture content is the dominant factor for those thermal parameters; and for the thermal diffusivity, there exists a critical soil moisture content about 22%~23%, when the soil moisture content is less than the critical value, thermal diffusivity is increasing with increase of soil moisture content. Contrarily, it is decreasing with increase of soil moisture content.