Seasonality of global and Arctic black carbon processes in the Arctic Monitoring and Assessment Programme models. Issue 12 (22nd June 2016)

• Record Type: Journal Article
• Authors: Mahmood, Rashed; von Salzen, Knut; Flanner, Mark; Sand, Maria; Langner, Joakim; Wang, Hailong; Huang, Lin
• Is Part Of: Journal of geophysical research. Volume 121:Issue 12(2016)
• Page Start: 7100
• Page End: 7116
• Publication Date: 2016-06-22
• Subjects: black carbon budgets -- transport -- wet scavenging -- aerosols -- Arctic pollution; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2016JD024849
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: This study quantifies black carbon (BC) processes in three global climate models and one chemistry transport model, with focus on the seasonality of BC transport, emissions, wet and dry deposition in the Arctic. In the models, transport of BC to the Arctic from lower latitudes is the major BC source for this region. Arctic emissions are very small. All models simulated a similar annual cycle of BC transport from lower latitudes to the Arctic, with maximum transport occurring in July. Substantial differences were found in simulated BC burdens and vertical distributions, with Canadian Atmospheric Global Climate Model (CanAM) (Norwegian Earth System Model, NorESM) producing the strongest (weakest) seasonal cycle. CanAM also has the shortest annual mean residence time for BC in the Arctic followed by Swedish Meteorological and Hydrological Institute Multiscale Atmospheric Transport and Chemistry model, Community Earth System Model, and NorESM. Overall, considerable differences in wet deposition efficiencies in the models exist and are a leading cause of differences in simulated BC burdens. Results from model sensitivity experiments indicate that convective scavenging outside the Arctic reduces the mean altitude of BC residing in the Arctic, making it more susceptible to scavenging by stratiform (layer) clouds in the Arctic. Consequently, scavenging of BC in convective clouds outside the Arctic acts to substantially increase the overall efficiency of BC wet deposition in the Arctic, which leads to low BC burdens and a more pronounced seasonal cycle compared to simulations without convective BC scavenging. In contrast, the simulated seasonality of BC concentrations in the upper troposphere is only weakly influenced by wet deposition in stratiform clouds, whereas lower tropospheric concentrations are highly sensitive. Key Points: Seasonal variations of black carbon (BC) mass budgets in the Arctic are simulated Good agreement in simulated annual mean transport of BC to the Arctic in models Convective wet removal is important for differences in modeled BC concentration