Using a global aerosol model adjoint to unravel the footprint of spatially-distributed emissions on cloud droplet number and cloud albedo

Abstract

The adjoints of the GEOS-Chem Chemical Transport Model and a comprehensive cloud droplet parameterization are coupled to study the sensitivity of cloud droplet number concentration (N d) over US regions and Central Europe to global emissions of anthropogenic fine mode aerosol precursors. Simulations reveal that the N d over the midwestern and southeastern US is mostly sensitive to SO 2 emissions during August, and to NH 3 emissions during February. Over the western US, N d is mostly sensitivity to SO 2 and primary organic aerosol emissions. In Central Europe, N d is most sensitive to NH 3 and NO x emissions. As expected, local emissions strongly affect N d; long-range transport, however, is also important for the western US and Europe. Emissions changes projected for the year 2050 are estimated to have the largest impacts on cloud albedo and N d over Central Europe during August (42% and 82% change, respectively) and western US during February (12% and 36.5% change, respectively). © 2012. American Geophysical Union. All Rights Reserved.