CCSM3 simulated regional effects of anthropogenic aerosols for two contrasting scenarios: Rising Asian emissions and global reduction of aerosols

This paper examines the effects of two largely contrasting aerosol emissions scenarios on regional climate using National Center for Atmospheric Research Community Climate System Model version 3: (1) increasing the anthropogenic aerosols over China and India by a factor of three and (2) reducing the global anthropogenic aerosols by a factor of 10. Dynamic footprints of the increased Asian aerosols with monthly variations are obtained from Model for OZone And Related chemical Tracers simulations. Increasing Asian aerosol emissions would result in cooling and reduction of precipitation over China and India, with large warming over the USA and southern Canada in winter and cooling in summer. Additionally, large changes in rainfall rate are identified over the tropical regions. In contrast, reducing the global aerosol emissions by a factor of 10 would significantly warm the atmosphere especially over the polluted land areas of both hemispheres. Increases in rainfall over polluted land areas are also noted. Deepening of the Aleutian low and weakening of the Icelandic low in winter are noted in the 500 mb geopotential height under both scenarios suggesting a strengthening of the North Pacific storm track and weakening of the North Atlantic Oscillation. The polar regions of winter hemisphere are subject to large changes in the 500 mb geopotential height. Teleconnection patterns associated with ENSO play important roles in causing large changes in surface air temperature and rainfall far away from the source regions of the altered aerosol concentrations.