Abstract
Abstract. Precipitation falling over the coastal regions of Antarctica often experiences low-level sublimation within the dry katabatic layer. The amount of water that reaches the ground surface is thereby considerably reduced. This paper investigates the synoptic conditions and the atmospheric transport pathways of moisture that lead to either virga – when precipitation is completely sublimated – or actual surface precipitation events over coastal Adélie Land, East Antarctica. For this purpose, the study combines ground-based lidar and radar measurements at Dumont d'Urville station (DDU), Lagrangian back trajectories, Eulerian diagnostics of extratropical cyclones and fronts, and moisture source estimations. It is found that precipitating systems at DDU are associated with warm fronts of cyclones that are located to the west of Adélie Land. Virga – corresponding to 36 % of the hours with precipitation above DDU – and surface precipitation cases are associated with the same precipitating system but they correspond to different phases of the event. Virga cases more often precede surface precipitation. They sometimes follow surface precipitation in the warm sector of the cyclone's frontal system, when the associated cyclone has moved to the east of Adélie Land and the precipitation intensity has weakened. On their way to DDU, the air parcels that ultimately precipitate above the station experience a large-scale lifting across the warm front. The lifting generally occurs earlier in time and farther from the station for virga than for precipitation. It is further shown that the water contained in the snow falling above DDU during pre-precipitation virga has an oceanic origin farther away (about 30∘ more to the west) from Adélie Land than the one contained in the snow that precipitates down to the ground surface.
Highlights
Precipitation is the main water input to the mass balance of the Antarctic ice sheet (e.g., King and Turner, 1997)
The present paper aims to study the synoptic conditions and the atmospheric moisture pathways that are associated with either surface precipitation or virga over Dumont d’Urville station (DDU) station in coastal Adélie Land
Warm air associated with the approaching warm front is located off DDU, while the cold sector of the extratropical cyclones is located to the west of Adélie Land during virga preprecipitation periods
Summary
Precipitation is the main water input to the mass balance of the Antarctic ice sheet (e.g., King and Turner, 1997). Grazioli et al (2017b) show that the relatively dry low-level katabatic winds blowing from the high plateau towards the ice sheet edges (Parish and Bromwich, 2007) sublimate a substantial part of the precipitation falling from overlying clouds Such results were confirmed and further investigated in Vignon et al (2019b) by inspecting the vertical profiles of relative humidity from radiosoundings over the coastal margins of East Antarctica. The present paper aims to study the synoptic conditions and the atmospheric moisture pathways that are associated with either surface precipitation or virga over DDU station in coastal Adélie Land.
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