Stable Isotope Variations in Monsoon Precipitation on the Tibetan Plateau
Stable Isotope Variations in Monsoon Precipitation on the Tibetan Plateau
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DOI：
10.2151/jmsj.79.959
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发表时间：
2001-10
影响因子：
3.1
通讯作者：
L. Tian;T. Yao;A. Numaguti;Weizheng Sun
中科院分区：
文献类型：
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作者：
L. Tian;T. Yao;A. Numaguti;Weizheng Sun
在青藏高原南北2,000 km以上的大尺度区域和9,000 km ~ 2的中尺度区域采集了降水样品，研究了季风降水对稳定同位素的影响。在大尺度区域内，沿青藏公路沿着由北向南多站采集降水和河水样品。结果表明，印度季风不仅影响降水中稳定同位素的空间变化，而且影响δ 18 O与δD的关系。降水受季风降水直接控制的地区氘含量（d）较低，而在青藏高原北方地区，由于受大陆性气团影响和当地较强的水文循环作用，d值较高。在中尺度上对那曲盆地降水中氧稳定同位素进行了详细的研究。6个观测点日降水中δ 18 O的时间变化趋势基本一致，表明青藏高原中部降水中δ 18 O的变化主要受大尺度天气条件的控制，而不是受局地气象因素的影响。流域降水中δ 18 O的空间变化与西藏尺度的空间变化趋势和当地的水文循环相一致。降水中δ 18 O的时间变化也与季风降水的移动有密切关系。初夏季风爆发导致δ 18 O值偏低。δ 18 O与南风指数呈负相关。高的SWI代表季风运动带来的南来水汽的强烈输送，与低的δ 18 O值相对应;低的SWI代表内陆气团水汽或局地蒸发水汽的输送，与高的δ 18 O值相对应。
Precipitation samples were collected in a large-scale region (more than 2,000 km from the north to the south of the Tibetan Plateau) and a middle scale region (with an area about 9,000 km2) in the Tibetan Plateau to study the impact of monsoon precipitation on stable isotopes. In the large-scale region, samples of precipitation and river water were collected at several stations from the north to the south along the Qinghai-Tibet Highway on the plateau. Results show that the Indian monsoon not only influences the spatial variation of stable isotope in precipitation, but also the relationship between δ18O and δD. Deuterium excees (d) in areas where precipitation is directly controlled by monsoon precipitation is lower, while in the northern Tibetan Plateau, d is in higher value due to the influence of continental air mass and strong local hydrological recycling. A detailed study on oxygen stable isotope in precipitation was carried out on the middle scale in the Nagqu Basin area. The temporal variation of δ18O in daily precipitation at 6 sites shows quite similar trends, indicating that δ18O in precipitation in the middle Tibetan Plateau is mainly controlled by large-scale synoptic condition, rather than the local meteorological factors. The spatial variation of δ18O in precipitation in the basin agrees with the Tibet-scale spatial variation trend and local hydrological recycling. Temporal variations of δ18O in precipitation also show a close relation to the movements of monsoon precipitation. The onset of monsoon in the earlier summer leads to low δ18O value. There is a negative relation between δ18O and SWI (south wind index). High SWI, which represents intensive transport of moisture from south with the monsoon movement, is coincided with lower δ18O values, while low SWI, which represents moisture from inland air mass or local evaporated moisture, is associated with higher δ18O values.