Comment on acp-2022-124

Abstract

Aerosol distributions have a potentially large influence on climate-relevant cloud properties but can be difficult to observe over the Arctic given pervasive cloudiness, long polar nights, data paucity over remote regions, and periodic diamond dust events that satellites can misclassify as aerosol. We compared Arctic 2008–2015 mineral dust and combustion aerosol distributions from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) reanalysis products, and the FLEX-ible PARTicle (FLEXPART) model. Based on Atmospheric Infrared Sounder (AIRS) satellite meteorological data, diamond dust may occur up to 60 % of the time in winter, but it hardly ever occurs in summer. In its absence, MERRA-2 and FLEXPART each predict the vertical distribution of combustion aerosols with relatively high confidence, as does FLEXPART for mineral dust. Comparisons to ground and satellite data suggest that MERRA-2 Arctic dust concentrations can be improved by the addition of local dust sources. Apparent false negative rates compared to lidar were substantially higher in conditions favouring diamond dust formation for both MERRA-2 and FLEXPART, as would be expected if CALIPSO were misclassifying diamond dust as mineral dust aerosols. All three products predicted that wintertime dust and combustion aerosols occur most frequently over the same Siberian regions where diamond dust is most common in the winter. This suggests that aerosol impacts on ice phase processes may be particularly high over Siberia, although further wintertime model validation with non-CALIPSO observations is needed. This assessment paves the way for applying the model-based aerosol simulations to a range of regional-scale Arctic aerosol-cloud interaction studies.