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Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica

P. Ricaud; M. Del Guasta; E. Bazile; N. Azouz; A. Lupi; P. Durand; J.-L. Attié; D. Veron; V. Guidard; P. Grigioni


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{
  "@context": "https://schema.org/", 
  "@id": "https://doi.org/10.5194/acp-20-4167-2020", 
  "@type": "ScholarlyArticle", 
  "creator": [
    {
      "@type": "Person", 
      "name": "P. Ricaud"
    }, 
    {
      "@type": "Person", 
      "name": "M. Del Guasta"
    }, 
    {
      "@type": "Person", 
      "name": "E. Bazile"
    }, 
    {
      "@type": "Person", 
      "name": "N. Azouz"
    }, 
    {
      "@type": "Person", 
      "name": "A. Lupi"
    }, 
    {
      "@type": "Person", 
      "name": "P. Durand"
    }, 
    {
      "@type": "Person", 
      "name": "J.-L. Atti\u00e9"
    }, 
    {
      "@type": "Person", 
      "name": "D. Veron"
    }, 
    {
      "@type": "Person", 
      "name": "V. Guidard"
    }, 
    {
      "@type": "Person", 
      "name": "P. Grigioni"
    }
  ], 
  "datePublished": "2020-04-01", 
  "description": "Abstract. A comprehensive analysis of the water budget over the Dome C (Concordia,\nAntarctica) station has been performed during the austral summer 2018\u20132019\nas part of the Year of Polar Prediction (YOPP) international campaign. Thin\n(\u223c100\u2009m deep) supercooled liquid water (SLW) clouds have been\ndetected and analysed using remotely sensed observations at the station\n(tropospheric depolarization lidar, the H2O Antarctica Microwave Stratospheric and Tropospheric\nRadiometer (HAMSTRAD), net\nsurface radiation from the Baseline Surface Radiation Network (BSRN)), radiosondes, and satellite observations (CALIOP, Cloud-Aerosol LIdar with Orthogonal Polarization/CALIPSO, Cloud Aerosol Lidar and Infrared\nPathfinder Satellite Observations) combined with a specific\nconfiguration of the numerical weather prediction model: ARPEGE-SH (Action\nde Recherche Petite Echelle Grande Echelle \u2013 Southern Hemisphere). The\nanalysis shows that SLW clouds were present from November to March, with the\ngreatest frequency occurring in December and January when \u223c50\u2009% of the days in summer time exhibited SLW clouds for at least 1\u2009h. Two case studies are used to illustrate this phenomenon. On 24\u00a0December\u00a02018, the atmospheric planetary boundary layer (PBL) evolved\nfollowing a typical diurnal variation, which is to say with a warm and dry\nmixing layer at local noon thicker than the cold and dry stable layer at\nlocal midnight. Our study showed that the SLW clouds were observed at Dome C\nwithin the entrainment and the capping inversion zones at the top of the\nPBL. ARPEGE-SH was not able to correctly estimate the ratio between liquid\nand solid water inside the clouds with the liquid water path (LWP) strongly\nunderestimated by a factor of 1000 compared to observations. The lack of\nsimulated SLW in the model impacted the net surface radiation that was 20\u201330\u2009W\u2009m\u22122 higher in the BSRN observations than in the ARPEGE-SH\ncalculations, mainly attributable to the BSRN longwave downward surface\nradiation being 50\u2009W\u2009m\u22122 greater than that of ARPEGE-SH. The second\ncase study took place on 20\u00a0December\u00a02018, when a warm and wet episode\nimpacted the PBL with no clear diurnal cycle of the PBL top. SLW cloud\nappearance within the entrainment and capping inversion zones coincided with\nthe warm and wet event. The amount of liquid water measured by HAMSTRAD was\n\u223c20 times greater in this perturbed PBL than in the typical\nPBL. Since ARPEGE-SH was not able to accurately reproduce these SLW clouds,\nthe discrepancy between the observed and calculated net surface radiation\nwas even greater than in the typical PBL case, reaching +50\u2009W\u2009m\u22122,\nmainly attributable to the downwelling longwave surface radiation from BSRN\nbeing 100\u2009W\u2009m\u22122 greater than that of ARPEGE-SH. The model was then run\nwith a new partition function favouring liquid water for temperatures below\n\u221220 down to \u221240\u2009\u2218C. In this test mode, ARPEGE-SH has\nbeen able to generate SLW clouds with modelled LWP and net surface radiation\nconsistent with observations during the typical case, whereas, during the\nperturbed case, the modelled LWP was 10 times less than the observations and\nthe modelled net surface radiation remained lower than the observations by\n\u223c50\u2009W\u2009m\u22122. Accurately modelling the presence of SLW\nclouds appears crucial to correctly simulate the surface energy budget over\nthe Antarctic Plateau.", 
  "headline": "Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica", 
  "identifier": "https://doi.org/10.5194/acp-20-4167-2020", 
  "image": "https://zenodo.org/static/img/logos/zenodo-gradient-round.svg", 
  "inLanguage": {
    "@type": "Language", 
    "alternateName": "eng", 
    "name": "English"
  }, 
  "keywords": [
    "Atmospheric Science"
  ], 
  "license": "https://creativecommons.org/licenses/by/4.0/", 
  "name": "Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica", 
  "url": "https://www.openaccessrepository.it/record/29299"
}
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