Model performance and surface impacts of atmospheric river events in Antarctica.

There is increasing evidence that atmospheric rivers (ARs) drive extreme precipitation and melt events across Antarctica and that these impacts are more accurately captured in high-resolution models. However, a comprehensive evaluation of AR impacts, comparing the performance of models with varying resolutions and physics across multiple AR events, has not yet been conducted. In this study, we simulate four recent AR events using the regional climate model HCLIM43 in its ALADIN (11 km) and AROME (11 km and 2.5 km) configurations, as well as ERA5 (31 km) and MERRA-2 (50 km), to analyze the dominant factors driving melt and precipitation and how spatial resolution and model physics affect surface impacts compared to observations. The events include intense snowfall and longwave radiation (Jun 2019), surface melt from foehn winds (Feb 2020), a large-scale heat anomaly driven by radiative and turbulent processes (Mar 2022), and inland surface warming after moisture is released by sea ice and ice shelves (Dec 2023). While all reanalyses and models underestimate surface warming and melt during these events, the high-resolution 2.5 km AROME configuration tends to simulate the most realistic precipitation and melt extents, largely due to its improved representation of foehn effects and reduced cloud biases. Longwave radiation generally dominates AR-induced warming, particularly over wider inland regions, while sensible heat fluxes are dominant in coastal and foehn-prone regions. Lastly, substantial differences among models/reanalyses in cloud phase and total cloud water paths underscore the need for improved cloud parameterizations and surface energy budget calculations.

Supplementary information: The online version contains supplementary material available at 10.1007/s44292-025-00026-w.