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Abstract:
Antarctic precipitation remains poorly characterised and understood, especially within the boundary layer. This is due in part to a still-limited amount of surface-based remote sensing observations. A suite of cloud and precipitation remote-sensing instruments including a W-band cloud radar and a K-band Micro Rain Radar (MRR) were used to characterise snowfall over Davis (69S, 78E). Surface snowfall events occurred when boundary layer wind speeds were weaker, temperatures were warmer, and relative humidity over ice higher, than when virga were present. The presence of virga is associated with Fohn conditions due to the location of Davis in the lee of an ice ridgeline. Dual wavelength ratio values from the summer indicate particle aggregation at temperatures of -14C to -10C, consistent with observations made elsewhere, including in the Arctic. In-cloud updrafts were stronger in summer than in winter at these temperatures. Larger downward velocities and the presence of super-cooled liquid layers suggest some rimed particles at warm temperatures above -10C during summer. Sublimation of snowfall mass aloft was 50\% between the accumulation peak at 1.2~km and 205~m altitude, which occurs within CloudSat's `blind zone'. An estimated lower bound of blowing snow fraction is 30%. Given the common prevailing winds and numerous ice ridgelines along much of the East Antarctic coastline, these Davis results can be used as a basis to further understand snowfall across the region.
