Simulations of Arctic winter stable-boundary layers during MOSAiC campaign using ICON-NWP and the influence of sea-ice roughness

The interaction between sea ice and atmosphere depends strongly on the exchange of momentum and heat in the Arctic boundary layer (BL). The representation of the Arctic BL is still a major source of uncertainty in recent climate models since they struggle to accurately model turbulent exchange in the predominantly stable-stratified BL of the Arctic. An additional source of uncertainty is the representation of sea-ice roughness in climate models. Sea-ice roughness is an important factor determining the mechanical production of turbulence. Here, we study the performance of the BL scheme of the numerical weather prediction model ICON-NWP and investigate the sensitivity to different values of sea-ice roughness. Therefore, we set-up ICON limited area simulations forced by ERA5 that include the track of the MOSAiC campaign in 2019-2020 and apply different values for the sea-ice roughness. ICON takes a constant roughness value for sea ice (default: 0.001 m) within a sea-ice tile whenever the ice thickness reaches a critical value. The results are compared to turbulence measurements during MOSAiC and we further investigate regional effects that occur in relation to the changed roughness values.