Water isotopologues, as natural tracers of the hydrological cycle on Earth, provide a unique way to assess the skill of climate models in representing realistic atmospheric-terrestrial water pathways. This study presents the newly developed WRF-Hydro-iso, which is a version of the coupled atmospheric-hydrological WRF-Hydro model enhanced with a joint soil-vegetation-atmospheric description of water isotopologue motions. It allows the consideration of isotopic fractionation processes during water phase changes in the atmosphere, the land surface, and the subsurface. For validation, WRF-Hydro-iso is applied to two different climate zones, namely Europe and Southern Africa under the present climate conditions. Each case is modeled with a domain employing a 5 km grid-spacing coupled with a terrestrial subgrid employing a 500 m grid-spacing in order to represent lateral terrestrial water flow. A 10-year slice is simulated for 2003–2012, using ERA5 reanalyses as driving data. The boundary condition of isotopic variables is prescribed with mean values from a 10-year simulation with the Community Earth System Model Version 1. WRF-Hydro-iso realistically reproduces the climatological variations of the isotopic concentrations and from the Global Network of Isotopes in Precipitation. In a sensitivity analysis, it is found that land surface evaporation fractionation increases the isotopic concentrations in the rootzone soil moisture and slightly decreases the isotopic concentrations in precipitation. Lateral terrestrial water flow minorly affects these isotopic concentrations through changes in evaporation-transpiration partitioning.

中文翻译：

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水同位素的土壤-植被-大气联合建模程序：WRF-Hydro-Iso 在不同气候区的实施和应用

水同位素体作为地球上水文循环的天然示踪剂，提供了一种独特的方法来评估气候模型在表示现实的大气-陆地水通路方面的技能。本研究介绍了新开发的 WRF-Hydro-iso，它是大气-水文 WRF-Hydro 耦合模型的一个版本，增强了土壤-植被-大气对水同位素运动的联合描述。它允许考虑大气、地表和地下水相变化期间的同位素分馏过程。为了验证，WRF-Hydro-iso 应用于两个不同的气候区，即在当前气候条件下的欧洲和南部非洲。每个案例都使用采用 5 km 网格间距的域与采用 500 m 网格间距的陆地子网格相结合，以表示横向陆地水流。使用 ERA5 再分析作为驱动数据，模拟了 2003-2012 年的 10 年切片。同位素变量的边界条件由社区地球系统模型第 1 版的 10 年模拟平均值规定。 WRF-Hydro-iso 真实地再现了同位素浓度的气候变化和来自全球降水同位素网络。在敏感性分析中，发现地表蒸发分馏增加了根区土壤水分中的同位素浓度，并略微降低了降水中的同位素浓度。横向陆地水流通过蒸发蒸腾分配的变化对这些同位素浓度产生轻微影响。