The effect of moisture source and synoptic conditions on precipitation isotopes in arid central Asia
The effect of moisture source and synoptic conditions on precipitation isotopes in arid central Asia
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DOI：
10.1002/2015jd024626
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
Sheng-jie Wang;Mingjun Zhang;J. Crawford;C. Hughes;Mingxia Du;Xuemei Liu
中科院分区：
文献类型：
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作者：
Sheng-jie Wang;Mingjun Zhang;J. Crawford;C. Hughes;Mingxia Du;Xuemei Liu
降水稳定同位素组成已广泛应用于示踪水汽来源。在西风主导的中亚地区，降水的同位素组成与地面气温有显著的相关性，温度效应被广泛接受。然而，同位素示踪水汽来源的意义在该地区尚不清楚，仍需要进一步的研究，使用事件为基础的观测。本文利用环天山地区的降水站网，研究了降水同位素的西风形势。虽然天山北方和南方盆地降水同位素的季节性相似，但南方盆地气候干旱，地形背风，水分输送较弱，氧同位素相对富集。在导致强降水的天气系统中，中亚涡旋更常见地导致降水中同位素比值的贫化，这与偏北水汽和/或地面水汽的贡献有关。特定湿度调整的拉格朗日诊断表明，在这种干旱气候中，南部盆地站的强降水通常具有相对局部的水分来源，并且从欧洲和中亚蒸发的陆地水分，而不是来自大西洋的海洋水分，更可能是直接的水分来源。对目标高度和比湿调节阈值进行了灵敏度分析。总体而言，调查结果不受不同条件的影响，水分更有可能来自当地，如较高的特定湿度阈值所示。
The stable isotope composition of precipitation has been widely applied to trace moisture sources. In the westerly dominated areas of central Asia, the isotopic composition of precipitation significantly correlates with surface air temperature, and the temperature effect is widely accepted. However, the significance of isotopes in tracing water vapor source is not clear for this region, and a further investigation using event‐based observations is still needed. Based on a network around the Tianshan Mountains, the westerly regime of precipitation isotopes is investigated. Although the seasonality of precipitation isotopes for the northern and southern basins of the Tianshan Mountains is similar, the more arid climate and leeward landform of the southern basin lead to weak moisture transport and relatively enriched oxygen isotopes. Of the synoptic systems resulting in heavy precipitation, the central Asian vortex more commonly leads to depleted isotopic ratios in precipitation, which is related to the contribution of northerly moisture and/or surface moisture. The specific humidity‐adjusted Lagrangian diagnostic indicates that the heavy precipitation on the southern basin stations usually has relatively local moisture sources in this arid climate and that terrestrial moisture evaporated from Europe and central Asia, rather than marine moisture from the Atlantic Ocean, is more likely to be the direct moisture source. A sensitivity analysis for target height and adjusting threshold of specific humidity is also applied to the improved Lagrangian diagnostic. Overall, the findings were unaffected by different conditions, and the moisture was more likely to be locally sourced, as indicated by higher specific humidity thresholds.