摘要
活动层土壤热状况是寒区陆面物理过程研究的重要内容之一。利用五道梁能量收支观测站1993年9月～2000年12月份实测辐射及土壤热通量资料结合五道梁气象站1961-2010时段的气象资料分析了近50 a来该地区活动层土壤的热状况。结果表明:五道梁地区土壤热通量有显著的年际、年代际变化;20世纪60～80年代,土壤热通量小于0.0 W/m2,活动层土壤以放热为主,自90年代以来,土壤热通量大于0.0 W/m2,活动层土壤以吸热为主。过去50 a中该地土壤热通量呈现增大趋势,平均每10 a土壤热通量增大0.31 W/m2。土壤热通量随净辐射的增大而增大。土壤热平衡系数的变化特点与土壤热通量的变化特点一致。60～80年代,活动层土壤热平衡系数<1,该地区冻土相对比较稳定,而自90年代以来此间土壤热平衡系数<1,表明该地多年冻土呈现出退化迹象。活动层土壤热平衡系数可表示为气温、地表温度及水汽压的函数。
The storage and release of heat in the soil of the QinghaiTibetan Plateau can trigger changes such as altering the troughridge allocation of the East Asian weather system. As a ＂buffer layer＂ betw in weather, een perma frost and the atmosphere, the active layer is sensitive to climate change, and responds quickly to temperature chang es. The active layer controls energy and water exchange between the soil and the atmosphere, which results from changes in soil water content and temperature. To some degree, it reflects the thermal condition of the underlying surface, and therefore it can be used as a thermal indicator of the plateau surface. Therefore, the thermal regime of active layer in the permafrost regions is very important aspect in the research of land surface processes in cold re gions. Thus more and more scholars focus their attentions on the thermal process of active layer. Limited by the ob servational data in situ, up to now it was not possible to exactly describe the thermal regime of freezethaw processes in active layer in the permafrost regions on the Plateau. Therefore, an indepth study of the soil thermodynamic prop erties of the active layer is needed. In this paper, the characteristics of soil heat flux and soil heat balance coefficient were analyzed by using the radiant data observed from September1993 to October 2000 and the meteorological data measured from January 1961 to October 2010 at WDL weather station located in the northern Tibetan Plateau. The results showed that the soil heat flux took on a clearly interannual and interdecadal variation features. The value of soil heat flux was less than 0.0 Wm2 throughout the time period from 1960s to 1980s. Correspondingly, the active layer soil released heat to atmosphere during this time period. While since the 1990s, soil heat flux was greater than 0.0 Wm2, which showed that in a year, there was surplus heat amount transferred from the surface to the lower soil layer, and the active layer soil here mainly absorbed heat in this time period. Generally, soil heat flux presented an increasing trend during the past 50 years at a rate of 0.31 Wm2 per decade. Soil heat flux increased with the increase of surface net radiation. As for the soil heat balance coefficient, it presented the similar characteristic as the soil heat flux. The values of soil heat balance coefficient of active layer were less than 1.0 during the time period from 1960s to 1980s, which indicated that the permafrost here was relatively stable during this time period. While such values were greater than 1.0 from 1990s to 2010s, which meant that heat amount absorbed by soil was bigger than that emitted by the soil. As a result, the active layer thickness in the study region increased 45 cm in recent 12 years; annual surface soil negative cumulative temperature and positive cumulative temperature exhibited a rising trend at rate of 193.4 148.8 Cd/10a and 148.8 Cd/10a, respectively; and the number of frozen days of active layer decreased by 8.9 days per decade. Such phenomenon suggested that the frozen ground took on a degenerate trend in study region. Finally an empirically derived model was proposed for estimating the soil heat balance coefficient over the northern Tibetan Plateau. It could be expressed as the function of air temperature, surface soil temperature and surface water vapor pressure. Verification results further ensured that the proposed model predicts values of soil heat balance coefficient accurately.
出处
《干旱区地理》
CSCD
北大核心
2013年第2期277-284,共8页
Arid Land Geography
基金
国家自然科学基金项目:青藏高原地表冻融循环过程中活动层热力参数的观测研究(41271081)
青藏高原多年冻土空间分布动态变化研究(41271086)
活动层冻融过程中青藏高原典型地段土壤热力学参数的动态变化研究(40871037)
青藏高原典型多年冻土区地气水热交换过程研究(40830533)
青藏高原南北界多年冻土对气候变化的响应研究(40901042)
冰冻圈科学国家重点实验室自主课题:青藏高原典型地段土壤热力学参数的研究(SKLCS-ZZ-2010-03)
科技部基础项目:青藏高原多年冻土本底调查(2008FY110200)
中国科学院百人计划:中亚多年冻土对气候变化的响应(51Y251571)
青海三江源自然保护区生态环境保护和建设工程生态监测本底-冻土监测及综合评估项目
关键词
长江源区
土壤热通量
土壤热平衡系数
river source region
soil heat flux
heat balance coefficient
