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. In this study, 8 years of high-resolution radiosonde data at nine Antarcticstations are analysed to provide the first large-scale characterization ofthe fine vertical structure of the low troposphere up to 3 km altitude overthe coastal margins of East Antarctica. Radiosonde data show a large spatialvariability of wind, temperature and humidity profiles, with differentfeatures between stations in katabatic regions (e.g., Dumont d'Urville andMawson stations), stations over two ice shelves (Neumayer and Halleystations) and regions with complex orography (e.g., McMurdo). At the Dumontd'Urville, Mawson and Davis stations, the yearly median wind speed profilesexhibit a clear low-level katabatic jet. During precipitation events, thelow-level flow generally remains of continental origin and its speed is evenreinforced due to the increase in the continent–ocean pressure gradient.Meanwhile, the relative humidity profiles show a dry low troposphere,suggesting the occurrence of low-level sublimation of precipitation inkatabatic regions but such a phenomenon does not appreciably occur over theice shelves near Halley and Neumayer. Although ERA-Interim and ERA5reanalyses assimilate radiosoundings at most stations considered here,substantial – and sometimes large – low-level wind and humidity biases arerevealed but ERA5 shows overall better performance. A free simulation withthe regional polar version of the Weather Research and Forecasting model(Polar WRF) (at a 35 km resolution) over the entire continent showstoo-strong and too-shallow near-surface jets in katabatic regions especiallyin winter. This may be a consequence of an underestimated coastal cold airbump and associated sea–continent pressure gradient force due to the coarse35 km resolution of the Polar WRF simulation. Beyond documenting thevertical structure of the low troposphere over coastal East Antarctica, thisstudy gives insights into the reliability and accuracy of two majorreanalysis products in this region on the Earth. The paper further underlinesthe difficulty of modeling the low-level flow over the margins of the icesheet with a state-of-the-art atmospheric model.

On the fine vertical structure of the low troposphere over the coastal margins of East Antarctica