陆面过程中稳定水同位素逐日变化的数学模拟--引入稳定同位素效应的CLM实例分析  

Simulations of Daily Variations of Stable Water Isotopes in Land Surface Process Using CLM Incorporating Stable Isotopic Effect

作　　者：章新平[1] 王晓云[2] 牛国跃 杨宗良 黄一民[1] 张剑明[1] 

机构地区：[1]湖南师范大学资源与环境科学学院,湖南长沙410081 [2]北京市气象局,北京100089 [3]Department of Geological Sciences, the University of Texas at Austin, Texas 78721-0254, USA

出　　处：《冰川冻土》2008年第1期100-107,共8页Journal of Glaciology and Geocryology

基　　金：湖南省重点学科建设项目(40652001);国家自然科学基金项目(40741002)资助

摘　　要：将稳定同位素效应引入CLM(Community Land Model),并对巴西马瑙斯站在平衡年的稳定水同位素的逐日变化进行模拟和分析.结果表明:降水、水汽和地表径流中1δ8O存在明显的季节变化,并与相应的水量存在显著的负相关关系,但凝结物中δ18O与地面凝结量存在显著的正相关关系,蒸发水汽中1δ8O与蒸发量之间无显著的相关关系.受土壤贮水削峰功能的影响,表层土壤和根区水中1δ8O的季节变化全无.植被层蒸发水汽中稳定同位素的丰度与大气的干湿程度存在密切联系:当降水量少时,大气干燥,植被层的蒸发较少,植被蒸发中1δ8O较高;当降水量较大时,空气湿润,植被层的蒸发量较大,蒸发中1δ8O则较低.植被蒸腾中1δ8O的变化与源区水体中1δ8O的变化保持一致,尤其是与根区水中的1δ8O.由于地下径流直接源自根区水的补充,因此,地下径流中1δ8O等于根区水中的δ18O.模拟结果还显示,降水MWL(大气水线)的梯度项和常数项均比全球平均MWL略偏小.尽管主要来自降水的贡献,但地表径流和植被层水体的MWLs与降水MWL存在较大的差异,这一方面与两类水体在蒸发过程中的稳定同位素的富集作用有关,另一方面与CLM模拟的水量有关.大气水汽线与降水的MWL的梯度值相近,说明大气水汽与降水近似处于稳定同位素平衡状态.另外,模拟的地面的凝结线与植被层的凝结线均与全球大气水线相近,且具有非常高相关程度,说明CLM的模拟是合理的.In this study, the daily variations of stable water isotopes in different reservoirs at Manaus, Brazil, are simulated and intercompared in an equilibrium year, using the Community Land Model （CLM） that is incorporated in stable isotopic effects as a diagnostic tool for an in-depth understanding of the hydrometeorological processes. The analyses show that the δ18O in precipitation, vapor and surface runoff have distinct seasonality with the marked negative correlations with corresponding water amount. However, the δ18O in surface dew displays marked positive correlation with the dew amount. As for the evaporation, no marked correlation exists between the δ18O in evaporation and evaporation amount. Impacted by reservoir regulation and peak attenuation of soil, the seasonality of δ18O in super-surface soil water and root-region water disappears. The isotopic a bundance in canopy evaporation depends on atmospheric humidity. On light precipitation and dry atmosphere, the δ18O in canopy evaporation is enhanced due to strong evaporation; on heavy precipitation and wet atmosphere, the δ18O in canopy evaporation declines due to weak evaporation. The δ18O variation in canopy transpiration keeps consistency with that in root-region water. Because the mass complementarity comes primarily from root- region water, the δ18O in subsurface runoff equals to that in root-region water. Compared with that of the global MWL, either the slope or the constant of the simulated MWL in precipitation is slightly smaller. Though originating from precipitation primarily, both the MWLs in surface runoff and in canopy reservoir have obvious difference from that in precipitation, which is related, on the one hand, to the stable isotopic enrichment rates of the two reservoirs in the process of evaporation, on the other hand, to the water amount simulated by CLM. However, the slope of the meteoric vapor line is close to that of MWL in precipitation, showing that atmospheric vapor and precipitation are in stable isotopic equilibrium s

关 键 词：稳定水同位素 CLM 模拟 大气水线 逐日变化 

分 类 号：P342[天文地球—水文科学]