Factors controlling stable isotope composition of precipitation in arid conditions: an observation network in the Tianshan Mountains, central Asia
Factors controlling stable isotope composition of precipitation in arid conditions: an observation network in the Tianshan Mountains, central Asia
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DOI：
10.3402/tellusb.v68.26206
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发表时间：
2016-02
期刊：
影响因子：
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通讯作者：
Sheng-jie Wang;Mingjun Zhang;C. Hughes;Xiaofan Zhu;Leilei Dong;Zhengguo Ren;Fen-li Chen
中科院分区：
文献类型：
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作者：
Sheng-jie Wang;Mingjun Zhang;C. Hughes;Xiaofan Zhu;Leilei Dong;Zhengguo Ren;Fen-li Chen
地球上大约三分之一的干旱地区分布在中亚。该区降水稳定同位素组成受干旱影响，蒸发量高，降水量低。为了研究中亚干旱地区降水中稳定水同位素的控制因素，2012年在天山周围建立了一个观测网络。基于2012-2013年23个站点的1052个事件降水样本，研究了降水中δD和δ 18 O的空间分布和季节变化。δD和δ 18 O值在夏季降水较多的月份（4 - 10月）相对较富集，在冬季较干燥的月份（11 - 3月）相对较贫乏，由于在许多最干燥的低海拔站观测到云下蒸发，δD和δ 18 O值较低。基于事件样本计算的当地大气降水线为δD=7.36δ 18 O- 0.50（r2=0.97，p<0.01），基于月降水加权值计算的当地大气降水线为δD=7.60δ 18 O +2.66（r2=0.98，p<0.01）。在冬季，这些数据表明，同位素雨影效应，从而导致降水在天山以南的最干旱地区的枯竭。各站δ 18 O值与气温呈显著正相关，最佳拟合方程为δ 18 O =0.78T - 16.01（r2=0.73，p<0.01）。利用0.5°（纬度）×0.5°（经度）网格化的逐日气温和降水资料，根据观测到的温度效应，制作了降水中δ 18 O的等值线图。
Approximately one-third of the Earth's arid areas are distributed across central Asia. The stable isotope composition of precipitation in this region is affected by its aridity, therefore subject to high evaporation and low precipitation amount. To investigate the factors controlling stable water isotopes in precipitation in arid central Asia, an observation network was established around the Tianshan Mountains in 2012. Based on the 1052 event-based precipitation samples collected at 23 stations during 2012–2013, the spatial distribution and seasonal variation of δD and δ18O in precipitation were investigated. The values of δD and δ18O are relatively more enriched in the rainfall dominant summer months (from April to October) and depleted in the drier winter months (from November to March) with low D-excess due to subcloud evaporation observed at many of the driest low elevation stations. The local meteoric water line (LMWL) was calculated to be δD=7.36δ18O – 0.50 (r2=0.97, p<0.01) based on the event-based samples, and δD=7.60δ18O+2.66 (r2=0.98, p<0.01) based on the monthly precipitation-weighted values. In winter, the data indicate an isotopic rain shadow effect whereby rainout leads to depletion of precipitation in the most arid region to the south of the Tianshan Mountains. The values of δ18O significantly correlate with air temperature for each station, and the best-fit equation is established as δ18O=0.78T – 16.01 (r2=0.73, p<0.01). Using daily air temperature and precipitation derived from a 0.5° (latitude)×0.5° (longitude) gridded data set, an isoscape of δ18O in precipitation was produced based on this observed temperature effect.