王圣杰|西北师范大学分享 http://www.blog.sciencetimes.com.cn/u/Z2112132 新疆降水同位素 Stable Water Isotopes in Arid Central Asia

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[转载]JH2018:降水量加权回归对大气水线的影响

已有 458 次阅读 2021-11-11 11:17 |个人分类:亚洲中部干旱区同位素|系统分类:论文交流|文章来源:转载

Shengjie Wang, Mingjun Zhang, Catherine E. Hughes, Jagoda Crawford, Gaofei Wang, Fenli Chen, Mingxia Du, Xue Qiu, Su’e Zhou. Meteoric water lines in arid Central Asia using event-based and monthly data. Journal of Hydrology, 2018, 562: 435–445. DOI: 10.1016/j.jhydrol.2018.05.034.

文献导读:

大气水线是同位素水文学的基本概念,通常利用多年的月尺度降水同位素数据得到。随着近年来监测技术的发展,基于短期采样的日尺度或事件尺度数据被广泛用于大气水线的计算,而不同时间分辨率大气水线的可比性值得探讨。文章以新疆天山23个站点的实测数据入手,对比了基于事件频次与月频次降水稳定同位素数据的大气水线,分析了干旱气候背景下小降水与强降水事件对大气水线的影响,指出了对于短期采样而言降水量加权方法对大气水线计算的重要性,文章有助于深入认识不同频次同位素数据用于水文研究的不确定性。

https://www.sciencedirect.com/science/article/pii/S0022169418303615



Highlights

Meteoric water lines in arid Central Asia impacted by below-cloud evaporation and re-evaporation of irrigation water.

Event-based data can provide more reliable LMWLs than monthly data for short campaigns.

A precipitation-weighted regression is preferred in arid and semi-arid climates.


Abstract

The local meteoric water line (LMWL) reflects the relationship between stable oxygen and hydrogen isotopes in precipitation, and is usually calculated using an ordinary least squares regression (OLSR). When event-based data are used to calculate a LMWL, the differences in precipitation amount of samples are not considered using OLSR, which in turn may influence the representativeness of the LMWL for local hydrology. Small rain events occur widely in arid Central Asia (annual mean precipitation <150 mm), and where smaller precipitation has lower deuterium excess, this results in LMWLs with slopes and intercepts lower than the global average. Based on an observation network of isotopes in precipitation across the Tianshan Mountains in arid Central Asia, LMWLs for 23 stations are calculated from event-based data from 2012 to 2013 (n = 978), using ordinary least squares, reduced major axis and major axis regressions and their precipitation-weighted counterparts. For the northern slope and mountainous areas, the LMWL slope and intercept are close to the Global Meteoric Water Line (GMWL), but the slope and intercept are lower for the southern slope indicating the greater dominance of sub-cloud evaporation. The effect of moisture recycling in the irrigated areas on the northern slope also can be seen where the LMWL slopes are >8. Using a precipitation weighted regression method with event-based data (especially precipitation-weighted reduced major axis regression, PWRMA) is generally consistent with the OLSR regression using monthly data. However, event-based datasets provide a wider range of values to better constrain the regression than can be achieved using monthly data over a short period, providing a sounder basis for determining LMWLs for relatively short-term sampling campaigns in an arid setting. The use of the PWRMA regression is preferred for determining the LMWL for the Tianshan Mountains, and results in a regional meteoric water line of δD = 7.9δ18O + 10.16.




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