摘要
气候是多年冻土形成与变化的动力,局地因素则通过改变地表辐射、对流和传导过程对多年冻土产生影响,导致多年冻土发生空间分异.应用青藏公路沿线大量的观测资料分析了局地因素对多年冻土区地温所产生的影响.结果表明:地形地貌、植被、积雪、土壤性质及含水量等局地因素,对青藏公路沿线地区多年冻土的发育和多年冻土热状况有显著影响.局地因素的差异可能会造成相同气候条件下小范围内冻土类型的分化,土壤颗粒较细、地表水分含量充足、植被发育良好的地段最有利于多年冻土的发育和保存.在植被覆盖和土壤性质相似的情况下,青藏高原地区多年冻土地温一般是西坡高于东坡,南坡高于北坡.暖季植被能够阻止部分热量进入土层,降低地表温度;在冷季,植被能减少土层热量散发,有助于保持地表温度.植被的存在有利于保持活动层以及其下多年冻土层的稳定,植被的退化会导致进入土层的热量发生变化引起季节冻结和融化的变化,并对多年冻土产生影响.冷季厚层积雪对多年冻土浅层土壤有显著的保温作用,而积雪融化会降低地表土壤温度.
As a result of water and energy exchange between atmosphere and soils through ground surface,permafrost takes place under a certain climatic conditions and local factors.Among them,climate is the driving force of permafrost formation and evolution,while local factors lead to regional differentia of permafrost distribution and thermal regime.The permafrost temperatures observed mainly along the Qinghai-Tibet Highway are used to analyze the influence of local factors on permafrost thermal regime,such as topography,geomorphology,vegetation,snow cover,soil property and water content.Permafrost distribution varies in regions with geologic landforms,vegetation type and hydrologic conditions even under the same climatic conditions.Local factors may cause the dissimilarity of permafrost in different regions.Permafrost temperatures differ a lot because of local factors even within a small area.Those regions which have finer soil grain,higher water content and better vegetation are more suitable for permafrost development and preservation.Ground temperatures on western slopes are higher than those on eastern slopes.Ground temperatures on southern slopes are higher than those on northern slopes.Vegetation prevents energy from entering the ground in the warm season and keeps ground surface cooling.While in the cold season,vegetation reduces the dissipation of heat.Vegetation keeps the active layer and permafrost stable.In desertification area,permafrost may degrade with thickening active layer and rising soil temperature.Thick snow insulates the ground from atmosphere during the cold season and keeps ground surface warm.The melting snow will cool the surface in warm season.
出处
《冰川冻土》
CSCD
北大核心
2011年第2期349-356,共8页
Journal of Glaciology and Geocryology
基金
国家重点基础研究发展计划(973计划)项目(2007CB4115052010CB951404)
国家自然科学基金项目(408305334090104240871037)资助
