Abstract
The local meteoric water lines (LMWLs) reflect water sources and the degree of sub-cloud evaporation at a specific location. Lanzhou is a semi-arid city located at the margin of the Asian monsoon, and the isotope composition in precipitation around this region has aroused attention in hydrological and paleoclimate studies. Based on an observation network of stable isotopes in precipitation in Lanzhou, LMWLs at four stations (Anning, Yuzhong, Gaolan and Yongdeng) are calculated using the event-based/monthly data and six regression methods (i.e., ordinary least squares, reduced major axis, major axis regressions, and their counterparts weighted using precipitation amount). Compared with the global meteoric water line, the slope and intercept of LMWL in Lanzhou are smaller. The slopes and intercepts calculated using different methods are slightly different. Among these methods, precipitation-weighted least squares regression (PWLSR) usually had the minimum average value of root mean sum of squared error (rmSSEav), indicating that the result of the precipitation weighted method is relatively stable. Higher precipitation amount and lower air temperature result in larger slopes and intercepts on an annual scale, which is out of accordance with the summertime.
Highlights
Published: 30 August 2021The stable isotope compositions in precipitation are widely investigated in Earth science [1,2,3]
At a global scale is termed as the global meteoric water line (GMWL; [4])
The local meteoric water lines (LMWLs) is usually established by an ordinary least squares regression (OLSR) [12], other regressions are recommended by IAEA
Summary
The stable isotope compositions in precipitation are widely investigated in Earth science [1,2,3]. There are strong linear relationships between stable hydrogen and oxygen compositions (δD and δ18 O) in natural water, and the best-fit line (δD = 8 δ18 O + 10). At a global scale is termed as the global meteoric water line (GMWL; [4]). Influenced by the evaporation condition at the source area as well as associated meteorological conditions [5], the local correlations between δD and δ18 O in precipitation vary. It is necessary to establish a local meteoric water line (LMWL) [6,7], which is potentially useful to assess water sources and the degree of sub-cloud evaporation [8].
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