HR: 17:00h
AN: A34B-05    [Abstracts]
TI: Modeling the Aging Process of Soot
AU: * Riemer, N
EM: nsriemer@stanford.edu
AF: Center for Turbulence Research, Stanford University, Stanford, U.S.A., Building 500 Stanford University, Stanford, CA 94305-3035 United States
AU: Vogel, H
EM: heike.vogel@imk.fzk.de
AF: Institut f\"{u}r Meteorologie und Klimaforschung Forschungszentrum Karlsruhe/ Universit\"{a}t Karlsruhe , Postfach 3640 , Karlsruhe, 76021 Germany
AU: Vogel, B
EM: bernhard.vogel@imk.fzk.de
AF: Institut f\"{u}r Meteorologie und Klimaforschung Forschungszentrum Karlsruhe/ Universit\"{a}t Karlsruhe , Postfach 3640 , Karlsruhe, 76021 Germany
AB: Soot particles contribute both to the direct and indirect climate effect. While freshly emitted soot is initially hydrophobic and externally mixed, it can be transferred into an internal mixture by coagulation, condensation or photochemical processes. These aging processes affect the hygroscopic qualities and hence the growth behaviour, the optical properties and eventually the lifetime of the soot particles. However, our understanding of these processes is still fragmentary. The aging process of soot is therefore one of the key uncertainties concerning the burden and effect of black carbon. In this study we carry out 3D simulations with the coupled mesoscale-gŸn model KAMM/DRAIS which provides a highly resolved boundary layer and allows for an explicit treatment of the aging process of soot by coagulation and condensation. The particle phase is treated with the aerosol model MADEsoot that calculates both the composition and the size distribution of the aerosol particles. Based on the results of our simulations, we derive the time scale on which soot is transferred from an external to an internal mixture. We focus on continental conditions in an industrialised environment and investigate two different meteorological scenarios, that is a summer and a winter episode. Generally, the aging time scales that we derive are smaller than most of the values that are currently used in global climate models and show a considerable variability in space and time. During daytime in summer, condensation of sulphuric acid is the governing process for the aging of soot. In wintertime, the formation of ammonium nitrate gains in importance. Overall, the time scales for daytime in summer and winter are comparable, about 2 h above 250 m and 8 h below During night time, condensation stops being the important process. Instead, coagulation becomes more significant, acting very slowly. This leads to a time scale during night of 10 to 40 h.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting