Unrealistically pristine air in the Arctic produced by current global scale models

Black carbon aerosol (BCA) in the Arctic has profound impacts on the global climate system through radiation processes. Despite its enormous impacts, current global scale models, powerful tools for estimating overall impact, tend to underestimate the levels of BCA in the Arctic over several seasons. Using a global aerosol transport simulation with a horizontal grid resolution of 3.5 km, we determined that a higher resolution significantly reduced the underestimation of BCA levels in the Arctic, mainly due to an enhancement of the representation of low-pressure and frontal systems. The BCA mass loading in the Arctic simulated with 3.5-km grid resolution was 4.2-times larger than that simulated with coarse (56-km) grid resolution. Our results also indicated that grid convergence had not occurred on both the contrast between the cloud/cloud free areas and the poleward BCA mass flux, despite the use of the 3.5-km grid resolution. These results suggest that a global aerosol transport simulation using kilometre-order or finer grid resolution is required for more accurate estimation of the distribution of pollutants in the Arctic.