Towards a Realistic Representation of Katabatic Storms in Greenland in Reanalysis Data and Global Earth System Models

Katabatic storms in southeastern Greenland are fierce, density-driven, downslope wind events with substantial implications for the local and downstream weather conditions and climate. This study presents a detailed assessment of their representation across three generations of global reanalysis products (ERA5, ERA-Interim, and ERA40) from the European Centre for Medium-Range Weather Forecasts, paired with a hierarchy of simulations at different grid resolutions with the Community Earth System Model version 2 (CESM2). Using the high-resolution (2.5-km resolution) Copernicus Arctic Regional Reanalysis (CARRA) as a benchmark, we find that the global reanalysis data sets systematically underestimate wind speeds (around 30% in ERA5 and 50% in ERA-Interim and ERA40) and fail to capture key structural features of these regional storms. Similar deficiencies are observed in CESM2 simulations when using standard latitude-longitude grids at 1–2 (Formula presented.) horizontal resolutions, which is a common model configuration used in recent iterations of the Coupled Model Intercomparison Projects. Variable-resolution configurations in CESM2 with enhanced representation of the Greenland topography demonstrate a marked improvement in capturing the strength and structure of these regional storms. Sensitivity simulations further confirm that steeper ice-sheet margins (better resolved at higher spatial resolution) are crucial for accurately representing katabatic acceleration. These findings underscore the importance of spatial resolution and realistic topographic representation in simulating local climate extremes. Accurately capturing such events is vital not only for understanding modern climate dynamics on and around the polar ice sheets, but likely also for simulating realistic ice sheet/Earth system interactions in glacial climates of the past.