Atmos. Chem. Phys., 13, 4339-4348, 2013
www.atmos-chem-phys.net/13/4339/2013/
doi:10.5194/acp-13-4339-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
The effects of hygroscopicity on ice nucleation of fossil fuel combustion aerosols in mixed-phase clouds
Y. Yun1,2, J. E. Penner1, and O. Popovicheva3
1Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48105, USA
2Atmospheric and Oceanic Sciences Program, Princeton University/Geophysical Fluid Dynamics Laboratory, 201 Forrestal Road, Princeton, NJ 08540, USA
3D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow 119234, Russia

Abstract. Fossil fuel black carbon and organic matter (ffBC/OM) are often emitted together with sulfate, which coats the surface of these particles and changes their hygroscopicity. Observational studies at cirrus temperatures (≈−40 °C) show that the hygroscopicity of soot particles can modulate their ice nucleation ability. Here, we implement a scheme for 3 categories of soot (hydrophobic, hydrophilic and hygroscopic) on the basis of laboratory data and specify their ability to act as ice nuclei at mixed-phase temperatures by extrapolating the observations using a published deposition/condensation/immersion freezing parameterization. The new scheme results in significant changes to anthropogenic forcing in mixed-phase clouds. The net forcing in our offline model studies varies from 0.111 to 1.059 W m−2 depending on the ice nucleation capability of hygroscopic soot particles. The total anthropogenic cloud forcing and whole-sky forcing with the new scheme are 0.06 W m−2 and −2.45 W m−2, respectively, but could be more positive (by about 1.17 W m−2) if hygroscopic soot particles are allowed to nucleate ice particles. The change in liquid water path dominates the anthropogenic forcing in mixed-phase clouds.

Citation: Yun, Y., Penner, J. E., and Popovicheva, O.: The effects of hygroscopicity on ice nucleation of fossil fuel combustion aerosols in mixed-phase clouds, Atmos. Chem. Phys., 13, 4339-4348, doi:10.5194/acp-13-4339-2013, 2013.
 
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