Stable isotopes of water (H₂O, HDO, and H₂¹⁸O) are tracers that provide powerful constraints on water transport processes in the atmosphere. This paper presents a description of an atmospheric boundary layer (ABL) simulation system called ISOLESC that couples water isotope fractionation processes with a land surface model, a large eddy simulation model, and a two‐moment cloud microphysics parameterization. Results from two model configurations—one with shallow precipitating cumulus and the other for a cloud‐free ABL—are presented to evaluate the model performance and determine its sensitivity to isotopic parameterizations. The coupled model successfully reproduces important ABL statistics (ABL height, cloud fraction, and cloud liquid water content), the expected effects of mixing and fractionation on the time evolution of ABL vapor isotopic composition, and observed diurnal variations of near‐surface water vapor isotopic composition. For the current configuration, nondiscriminating entrainment contributes 17% to the subdaily time variation of near‐surface vapor deuterium excess, while surface evapotranspiration contributes 83%. The isotopic compositions of water vapor and cloud water are insensitive to mesh resolution, but the profiles of cloud water specific humidity, rainwater specific humidity, and its isotopic ratios show moderate response to changes in grid size. Since ISOLESC resolves the energy containing scales of turbulent motions in the ABL and incorporates microphysical processes, it can be used for constraining ABL parameterizations. We find that a further improvement of raindrop reevaporation in the current cloud microphysical scheme is required in order to produce realistic near‐surface raindrop deuterium excess for the case simulated here. We suggest that ISOLESC provides a quantitative framework for utilizing vapor‐phase isotopic measurements to study local hydrological processes.

中文翻译：

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ISOLESC：同位素-LSM-LES-云耦合建模系统，用于研究大气边界层的水量预算

水的稳定同位素（H ₂ O，HDO和H ₂ ¹⁸O）是对大气中水传输过程提供强大约束的示踪剂。本文介绍了一种称为ISOLESC的大气边界层（ABL）模拟系统，该系统将水同位素分馏过程与陆面模型，大型涡流模拟模型和两步云微物理参数化结合在一起。提出了两种模型配置的结果，一种具有浅沉淀积云，另一种则无云ABL，用于评估模型性能并确定其对同位素参数化的敏感性。耦合模型成功地重现了重要的ABL统计数据（ABL高度，云量和云水含量），混合和分馏对ABL蒸气同位素组成的时间演变的预期影响，并观察到近地表水汽同位素组成的日变化。对于当前配置，非歧视性夹带对近地表蒸气氘过量的亚时间变化贡献了17％，而表面蒸散量贡献了83％。水蒸气和云水的同位素组成对网格分辨率不敏感，但是云水比湿度，雨水比湿度及其同位素比的分布图显示出对网格大小变化的中等响应。由于ISOLESC解析了ABL中湍流运动的能量尺度，并结合了微物理过程，因此可以用于约束ABL参数化。我们发现，在当前的云微物理方案中，需要进一步改善雨滴的再蒸发，以便在此处模拟的情况下产生逼真的近地表雨滴氘。我们建议ISOLESC为利用气相同位素测量研究局部水文过程提供一个定量框架。