Time series of the summertime diurnal variability in the atmospheric water vapour isotopic composition at Concordia station, East Antarctica

Abstract. Measurements of stable water isotopes in the atmospheric water vapour can be used to better understand the physical processes of the atmospheric water cycle. In polar regions, it is a key parameter to understand the link between the precipitation and snow isotopic compositions and interpret isotope climate records from ice cores. In this study we present a novel 2.5-month record of the atmospheric water vapour isotopic composition during the austral summer 2023–2024 at Concordia Station (East Antarctica), from two independently calibrated laser spectrometers (CRDS and OF-CEAS measurement techniques) which are optimised to measure in low humidity environments. We show that both instruments accurately measure the summertime diurnal variability in the water vapour 𝛿¹⁸O, 𝛿D, and d-excess when the water vapour mixing ratio is higher than 200 ppmv. We compare these measurements to the outputs of the isotope-enabled atmospheric general circulation model LMDZ6-iso and show that the model exhibits biases in both the mean water vapour isotopic composition and the amplitude of the diurnal cycle, consistent with previous studies. Hence, this study provides a novel dataset of the atmospheric water vapour isotopic composition on the Antarctic Plateau, which can be used to evaluate isotope-enabled atmospheric general circulation models. The dataset is available on the public repository Zenodo (https://doi.org/10.5281/zenodo.14569655, Landais et al., 2024b).