Articles | Volume 17, issue 1
Atmos. Chem. Phys., 17, 691–704, 2017
Atmos. Chem. Phys., 17, 691–704, 2017

Research article 13 Jan 2017

Research article | 13 Jan 2017

Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

Christophe Genthon1, Luc Piard1, Etienne Vignon1, Jean-Baptiste Madeleine2,3, Mathieu Casado4, and Hubert Gallée1 Christophe Genthon et al.
  • 1Univ. Grenoble Alpes, CNRS, IRD, IGE, 38000, Grenoble, France
  • 2Sorbonne Universités, UPMC Univ. Paris 06, UMR 8539, Laboratoire de Météorologie Dynamique (IPSL), 75005, Paris, France
  • 3CNRS, UMR 8539, Laboratoire de Météorologie Dynamique (IPSL), 75005, Paris, France
  • 4LSCE-IPSL, CEA-CNRS-UVSQ-U. Paris-Saclay, Gif-sur-Yvette, France

Abstract. Supersaturation often occurs at the top of the troposphere 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 parameterizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation 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 sublimation 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 supersaturation 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.

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Short summary
Natural atmospheric supersaturation is a norm rather than an exception at the surface of Dome C on the Antarctic Plateau. This is reported by hygrometers adapted to perform in extreme cold environments and avoid release of excess moisture before it is measured. One year of observation shows that atmospheric models with cold microphysics parameterizations designed for high altitude cirrus reproduce frequently but fail with the detailed statistics of supersaturation at the surface of Dome C.
Final-revised paper