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The influence of orographic gravity waves on precipitation during an atmospheric river event at Davis, Antarctica
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  • Josué Gehring,
  • Etienne Vignon,
  • Anne-Claire Billault-Roux,
  • Alfonso Ferrone,
  • Alain Protat,
  • Alexander Simon P,
  • Alexis Berne
Josué Gehring
EPFL

Corresponding Author:[email protected]

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Etienne Vignon
Laboratoire de Météorologie Dynamique/IPSL/Sorbone Université/CNRS
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Anne-Claire Billault-Roux
EPFL
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Alfonso Ferrone
EPFL
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Alain Protat
Bureau of Meteorology
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Alexander Simon P
Australian Antarctic Division
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Alexis Berne
EPFL
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Abstract

Intense snowfall sublimation was observed during a precipitation event over Davis in the Vestfold Hills, East Antarctica, from 08 to 10 January 2019. Radar observations and simulations from the Weather Research and Forecasting model revealed that orographic gravity waves (OGWs), generated by a north-easterly flow impinging on the ice ridge upstream of Davis, were responsible for snowfall sublimation through a Foehn effect. Despite the strong meridional moisture advection associated with an atmospheric river (AR) during this event, almost no precipitation reached the ground at Davis. We found that the direction of the synoptic flow with respect to the orography determined the intensity of OGWs over Davis, which in turn directly influenced the snowfall microphysics. Turbulence induced by the OGWs likely enhanced the aggregation process, as revealed by dual-polarization and dual-frequency radar observations. This study suggests that despite the intense AR, the precipitation distribution was determined by local processes tied to the orography. The mechanisms found in this case study could contribute to the extremely dry climate of the Vestfold Hills, one of the main Antarctic oasis.