Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic PlateauReport as inadecuate

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1 UGA - Université Grenoble Alpes 2 LMD - Laboratoire de Météorologie Dynamique 3 LSCE - Laboratoire des Sciences du Climat et de l-Environnement Gif-sur-Yvette

Abstract : Supersaturation often occurs at the top of the tro-posphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and-or ice condensation nuclei. One exception is the surface of the high Antarctic Plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic Plateau is presented. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content, even in the case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the Antarctic Plateau are thus likely biased low. The measurements are compared with results from two models implementing cold microphysics parame-terizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model At-mosphérique Régional. As in the observations, supersatura-tion is frequent in the models but the statistical distribution differs both between models and observations and between the two models, leaving much room for model improvement. This is unlikely to strongly affect estimations of surface sub-limation because supersaturation is more frequent as temperature is lower, and moisture quantities and thus water fluxes are small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric su-persaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high-altitude cirrus clouds in meteorological and climate models.

Author: Christophe Genthon - Luc Piard - Etienne Vignon - Jean-Baptiste Madeleine - Mathieu Casado - Hubert Gallée -



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