Numerical experiments on the impacts of surface evaporation and fractionation factors on stable isotopes in precipitation

Abstract

The isotope enabled atmospheric water balance model is applied to examine the spatial and temporal variations of δ 18 O in precipitation, amount effect and meteoric water lines (MWL) under four scenarios with different fractionation nature and surface evaporation inputs. The experiments are conducted under the same weather forcing in the framework of the water balance and stable water isotope balance. Globally, the spatial patterns of mean δ 18 O and global MWLs simulated by four simulation tests are in reasonably good agreement with the Global Network of Isotopes in Precipitation observations. The results indicate that the assumptions of equilibrium fractionation for simulating spatial distribution in mean annual δ 18 O and the global MWL, and kinetic fractionation in simulating δ 18 O seasonality are acceptable. In Changsha, four simulation tests all reproduce the observed seasonal variations of δ 18 O in precipitation. Compared with equilibrium fractionation, the depleted degree of stable isotopes in precipitation is enhanced under kinetic fractionation, in company with a decrease of isotopic seasonality and inter-event variability. The alteration of stable isotopes in precipitation caused by the seasonal variation of stable isotopes in vapour evaporated from the surface is opposite between cold and warm seasons. Four simulations all produce the amount effect commonly observed in monsoon areas. Under kinetic fractionation, the slope of simulated amount effect is closer to the observed one than other scenarios. The MWL for warm and humid climate in monsoon areas are well simulated too. The slopes and intercepts of the simulated MWLs decrease under kinetic fractionation.

Differential isotopic characteristics of eco‐hydrologic processes in a subtropical watershed, China

“…Stable isotope values in precipitation generally depend on a host of atmospheric and geographic parameters, such as precipitation amount as well as temperature, latitude, altitude, and distances to the coast (Koeniger, Toll, & Himmelsbach, ; van Geldern, Kuhlemann, Schiebel, Taubald, & Barth, ). These isotopic effects and their spatial variability are associated with moisture sources, rainout history, and atmospheric conditions that lead to precipitation (Dansgaard, ; J. R. Liu et al, ; Zhang, Guan, Zhang, Zhang, & Yao, ).…”

Isotope composition of daily precipitation from 2019 to 2020 in Sanming, southeastern China

“…Craig (1961) first reported the regression line δ 2 H = 8 * δ 18 O + 10 as the global meteoric water line (GMWL) based on the positive connection between δ 2 H and δ 18 O found in natural meteoric waters throughout the world. With the increased Frontiers in Environmental Science frontiersin.org establishment of GNIP program stations, numerous LMWLs have been built (Merlivat and Jouzel, 1979;Araguás-Araguás et al, 1998;Zhang et al, 2016;Wu et al, 2022). Although there are considerable geographical differences in climatic characteristics and sources of water vapor, the slope of the LMWL and GMWL are still in agreement.…”

Coupled Effects of Moisture Transport Pathway and Convection on Stable Isotopes in Precipitation across the East Asian Monsoon Region: Implications for Paleoclimate Reconstruction

“…The observed daily d 18 O p data from Guangzhou and Changsha from January 2010 to December 2013 (4 years) were obtained from the National Tibetan Plateau Data Center and previous studies (Wu et al 2015;Zhang et al 2016;Yang et al 2017) (see Text S2 for details). In addition, we collected daily precipitation samples and analyzed the daily d 18 O p data at both Shijiazhuang and Changchun from January 2010 to December 2013 (Table S1).…”