[en] Atmospheric rivers (ARs) are strong intrusions of moisture and heat that play a fundamental role in the Antarctic surface mass and energy balance. Despite that 90% of the moisture transfer from mid-latitudes to the poles is caused by ARs, the characteristics and the impacts of these events are still poorly understood in Antarctica. Our study focuses on the ARs affecting the Antarctic Peninsula (AP) during 7-8 and 21-22 February 2022, which led to positive temperature records and heavy rainfall on the AP, respectively. The objectives of this study are to understand how these ARs are embedded into the large-scale atmospheric circulation, and to improve our understanding of the contribution of ARs to moisture transport and their representation in models.
The study is based on the dataset collected during the field campaign at the AP (Vernadsky and Escudero stations) in January-March 2022, including radiosonde/weather observations, and isotopic measurements of precipitation, combined with ERA5 reanalysis and high-resolution simulation by regional climate model MAR. The 500-hPa geopotential height anomalies (from ERA5) show a positive phase of the Southern Annular Mode. February also shows a strong positive integrated vapor transport (IVT) anomaly in the southern central Pacific corresponding to the sea surface temperature and evaporation anomalies. The back-trajectory analysis combined with ERA5 thermodynamic parameter changes along the trajectories of the first AR event showed that subtropical central Pacific played an important role in supplying moisture at the Vernadsky site at the level of precipitation formation where the melt layer was observed. In contrast, for the second AR event, the moisture source was more confined to the southeast Pacific and in midlatitudes. The analysis of the isotopic signatures from precipitation samples collected at both sites is ongoing and will be used to validate/interpret moisture sources and air mass transformation along the way.
