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干旱区地理 ›› 2019, Vol. 42 ›› Issue (4): 790-798.doi: 10.12118/j.issn.1000-6060.2019.04.10

• 气候与水文 • 上一篇    下一篇

黄河流域降水稳定同位素的云下二次蒸发效应

车存伟1,张明军1,王圣杰1,2,杜勤勤1,邱雪1,马荣1   

  1. 1西北师范大学地理与环境科学学院,甘肃兰州730070; 2陕西省河流湿地生态与环境重点实验室,陕西渭南714099
  • 收稿日期:2019-01-05 修回日期:2019-04-01 出版日期:2019-07-25 发布日期:2019-07-24
  • 通讯作者: 张明军(1974 -),男,教授,研究方向为气候变化与水文过程.Email:mjzhang2004@163.com
  • 基金资助:
    国家自然科学基金(41461003,41771035);甘肃省高等学校创新团队项目(2018C-02);陕西省河流湿地生态与环境重点实验室开发基金项目(SXSD201703)

Influence of subcloud secondary evaporation on stable isotope composition in precipitation in the Yellow River Basin

CHE Cunwei1,ZHANG Mingjun1,WANG Shengjie1,2,DU Qinqin1,QIU Xue1,MA Rong1   

  1. 1College of Geography and Environmental Science,Northwest Normal University,Lanzhou 730070,Gansu,China; 2Key Laboratory for Ecology and Environment of River Wetlands in Shaanxi Province,Weinan 714099,Shaanxi,China
  • Received:2019-01-05 Revised:2019-04-01 Online:2019-07-25 Published:2019-07-24
  • About author:车存伟(1994 -),男,硕士研究生,研究方向为全球变化与可持续发展.Email:geoche2017@126.com

摘要: 雨滴从云底降落到地面过程的云下二次蒸发现象会影响雨滴中的同位素比率,明确降水过程中稳定同位素的变化对研究流域水循环具有重要意义。基于全球降水同位素网络(GNIP)、相关文献同位素数据以及气象数据,首先建立局地大气水线(LMWL)定性分析了黄河流域云下二次蒸发与各气象要素间的关系,其次运用改进的Stewart模型定量计算了蒸发剩余比(f)和云底降水与地面降水的D-excess之差(Δd)。结果表明:(1) 黄河流域LMWL方程为:δ2H=7.01δ18O+1.25(n=293,R2=0.92),斜率和截距相比GMWL均较小,说明雨滴在下落过程中受到云下二次蒸发的影响。其中0~10 mm的降雨事件对云下二次蒸发影响显著;气温越高,或者水汽压、相对湿度越小,云下二次蒸发越强烈。(2) 季节变化上,从春季到冬季, f和Δd逐渐增大,云下二次蒸发逐渐减小。空间变化上,蒙甘区、蒙中区、晋陕甘区和渭河区的西安,年际间云下二次蒸发变化较大,而青南区、祁连-青海湖区、渭河区的平凉、长武、华山和鲁淮区年际差异较小。(3) 降水中Δdf之间的线性关系在不同气象要素范围内有不同的数值,由于不同区域各气象条件存在差异,因此在应用经验公式时需考虑研究区的具体气象条件。

关键词: 稳定氢氧同位素, 云下二次蒸发, 降水, 黄河流域

Abstract: The subcloud secondary evaporation of raindrops which happens during their falling process from the cloud base to the ground affects the stable isotopic ratios in the raindrops.It is of great significance to understand the changes of the stable isotopes in precipitation in the study of water cycle in a watershed.In this paper,the isotope data in precipitation were acquired from the Global Network of Isotopes in Precipitation(GNIP)and the related literatures across the Yellow River Basin.The relationship between subcloud secondary evaporation and meteorological elements was analyzed using local meteoric water line(LMWL).Based on an improved Stewart model,the change of the evaporation remaining ratios of raindrops (f) and the difference of Dexcess from subcloud to ground(Δd)were quantitatively calculated.In this model,the heights of falling raindrops were estimated as lifting condensation level(LCL)using the insitu meteorological measurements.The stations cover the main climate zones across the Yellow River Basin,which can represent an integrated pattern of subsecondary evaporation in the study region.The results showed that the LMWL of the Yellow River Basin isδ2H=7.01δ18O+1.25(n=293, R2=0.92),and both the slope and the intercept of LMWL are smaller than that of the global meteoric water line(GMWL),which indicates that precipitation isotopes are affected by the subcloud secondary evaporation.The precipitation of 0~10 mm per month indicates a significant subcloud evaporation effect.And the higher air temperature (or the lower vapor pressure and relative humidity) may result in the greater subcloud secondary evaporation.There was an obvious seasonality of evaporation remaining ratio and Dexcess changes in the basin.From spring to winter, f and Δd were gradually increased,and subcloud secondary evaporation was gradually decreased.According to the climate zoning in China,the larger interannual variability in subcloud evaporation was exhibited in the subregions of Inner MongoliaGansu,Central Inner Mongolia,ShanxiShaanxiGansu and part of Weihe River (especially Xi’an).In contrast,smaller interannual trend was seen in the subregions of northern Qinghai,Qilian MountainsQinghai Lake,part of Weihe River (Pingliang,Changwu and Huashan),and ShandongHuaihe River.The linear relationship between Δd and f was different under various meteorological conditions as well as geographic locations,and the regression coefficient in the empirical formula should be treated according to local meteorological backgrounds.

Key words: stable isotopes of hydrogen and oxygen, subcloud secondary evaporation, precipitation, the Yellow River Basin