Spatiotemporal Variations in Summertime Arctic Aerosol Optical Depth Caused by Synoptic‐Scale Atmospheric Circulation in Three Reanalyses

Atmospheric aerosol affects the radiation budget, cloud cover and properties, and surface albedo of sea ice and snow over the Arctic with obvious climatological significance. However, observations are scarce and have large uncertainties. Aerosol optical depth (AOD) variability in the Arctic and its relationship with atmospheric disturbances on synoptic timescales were investigated on the basis of the JRAero, CAMSRA, and MERRA2 reanalyses. Total AODs of the three reanalyses were spatiotemporally consistent in summer, although contributions of individual aerosol species differed. Summertime AOD variability was strongly correlated with observations in all reanalyses. The predominance of organic carbon aerosol indicates that aerosols are derived mainly from biomass burning over northern Eurasia and northern North America. Differences in composites of atmospheric fields between high‐ and low‐loading days indicate that locations of synoptic disturbances are related to high‐AOD events in the Arctic. Furthermore, empirical orthogonal function analysis indicates that the first‐ and second‐largest AOD variabilities in synoptic timescales occur over northern Eurasia. This AOD variability is related to two different types of Arctic cyclone, the development of which is important in aerosol transport, aging, and deposition in summer. Plain Language Summary Atmospheric aerosol plays a crucial role in the Arctic climate system. Aerosol affects radiation budget directly, via aerosol–cloud interactions, and by changing surface albedo of snow and sea ice. Based on three reanalyses, we analyzed the relationship between aerosol optical depth (AOD) variability and synoptic‐scale atmospheric disturbances in the Arctic. For the three reanalyses, summertime AODs were spatiotemporally consistent, although contributions of individual aerosol species varied. High‐AOD events are derived mainly from biomass burning over northern Eurasia and northern North America, and are related to the location of synoptic disturbances. AOD variability is greatest over northern Eurasia, where the moisture and precipitation fields within the Arctic cyclones play essential roles in aerosol transport and deposition. Key Points Arctic summertime synoptic variability of total aerosol optical depth (AOD) strongly correlated with observations in three reanalyses Location and development of synoptic disturbances has a predominant effect on the poleward transport, aging, and deposition of aerosols Primary and