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Abstract:
We investigated a heavy snowfall event in Dronning Maud Land (DML), East Antarctica, on November 8th and 9th, 2015, which contributed to 20% of the total annual accumulation. The anomalous moisture transport during the event was due to a strong atmospheric river, a long, narrow band of high moisture that travelled poleward from 30-40S in the South Atlantic Ocean. The synoptic scale pattern consisted of an anomalous blocking ridge extending to the Antarctic continent and a deep cyclonic system that intruded into the area. The main moisture source was in an area of anomalous evaporation in the South Atlantic Ocean 4-5 days prior to the event. The eastward movement of this anomaly and the strengthening of the low-pressure system in the Atlantic Ocean favoured a band of high moisture transport towards DML. A regional atmospheric model optimized for the polar regions (Polar WRF) was used to examine the relationship between the complex coastal topography of DML and the spatial distribution of precipitation during the event. The model showed reasonable skill in simulating the surface meteorological conditions, and vertical cross-section analysis showed that most precipitation was confined to regions with steep topography in the path of the atmospheric river, causing a sudden updraft of maritime air when interacting with these regions. This case study of a heavy precipitation event shows that anomalous moisture uptake in the Atlantic Ocean results in extended moisture transport to coastal DML, leading to heavy snowfall due to interaction with steep topography.
