Linking cloud hydrometeor growth and surface precipitation to synoptic forcing at Dumont d’Urville, East Antarctica

Abstract. We investigate how weather regimes influence surface precipitation and associated cloud microphysical processes at Dumont d’Urville (DDU; 66.7° S, 140.0° E) using data from the Antarctic Precipitation: Remote Sensing from Surface and Space (APRES3) project. Two precipitation-producing regimes, Summer Warm Air Advection (S-WAA) and Low-Pressure (Low-P), account for 94.2 % of total precipitation at DDU. Hydrometeor growth processes were analysed through comprehensive case studies of Low-P and S-WAA events. The polarimetric signatures during the Low-P event indicate riming and secondary ice production (SIP) within the −10 to −14 °C layer (2–3.5 km), which falls within the dendritic growth zone (DGZ; approximately −10 to −20 °C). Riming intensifies between 1 and 2 km (−7 to −10 °C), whereas below 1 km, downslope flow leads to pronounced hydrometeor sublimation and sublimation-induced SIP. Thus, the surface precipitation associated with this event displays an intermittent pattern, with a predominance of graupel. In contrast, the S-WAA regime is associated with a moist boundary layer, favouring persistent surface precipitation. The polarimetric signatures in the upper half of the DGZ (−14 to −20 °C, 2.5–3.5 km) suggest hydrometeor growth through vapour deposition, while signatures below down to 1 km (−8 to −14 °C) align with aggregation processes. Enhanced riming and SIP driven by the Hallett–Mossop process are observed below 1 km. Our findings emphasise that synoptic weather regimes primarily impact precipitation growth, while boundary-layer flow and moisture play a significant role in snowfall efficiency at DDU in East Antarctica.