Sensitivity Studies and Evaluation of km-Scale ICON Atmospheric Simulations against MOSAiC Observations During the Arctic Winter

The Arctic has experienced a pronounced and accelerated warming over recent decades, and changes over Arctic regions may  influence mid-latitude atmospheric dynamics and weather as well. However, climate models usually struggle to accurately simulate the Arctic climate, particularly key processes such as intermittent turbulence under stably stratified Arctic conditions or the occurrence of liquid-bearing mixed-phase clouds.

Here, we focus on the configuration of the ICON atmospheric model currently developed within the WarmWorld project, applied in a limited-area setup at a horizontal resolution of 5km, centered  on the research vessel Polarstern during the MOSAiC expedition in winter 2019/20. This setup allows for an evaluation of the model’s default performance under Arctic winter conditions and facilitates the identification of pronounced yet common model biases, such as cold surface temperatures and excessive near-surface stability arising from deficiencies in the representation of supercooled liquid-bearing clouds. In particular, we investigate how changes in model resolution and adaptations to the turbulent surface-flux parameterization over sea ice under stably stratified Arctic conditions affect the lower Arctic boundary layer and may help to mitigate model biases.