HR: 09:00h
AN: A51G-04    [Abstracts]
TI: The Microphysical Link between Non-Absorbing Anthropogenic Aerosols and Atmospheric Absorption
AU: * Stier, P
EM: philip.stier@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125
AU: Feichter, J
EM: feichter@dkrz.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146 Germany
AU: Kinne, S
EM: kinne@dkrz.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146 Germany
AU: Boucher, O
EM: olivier.boucher@metoffice.gov.uk
AF: United Kingdom Met Office, FitzRoy Road, Exeter, EX1 3PB United Kingdom
AB: The absorption of solar radiation by atmospheric aerosol is recognized to affect global and regional climate. In particular the absorption by anthropogenic black carbon (BC) has recently received considerable attention. Previous studies of the influence of other, potentially non-absorbing, aerosol components on BC absorption focused either on the absorption enhancement by internal mixing or on the absorption reduction by a decrease of the BC load due to enhanced microphysical aging. Here we present an analysis of the importance of anthropogenic sulfate on atmospheric absorption by these two mechanisms, based on a comprehensive modelling framework. Embedded in the ECHAM5 GCM, the microphysical aerosol module HAM provides a prognostic treatment of the aerosol composition, size-distribution, and mixing state for a superposition of log-normal modes. Our findings demonstrate the significance of both mechanisms on the global scale with a regional separation depending on the distance from the aerosol sources. Enhanced microphysical aging and the associated reduction of the atmospheric black carbon load decreases atmospheric solar absorption in the remote transport regions. However, internal mixing of black carbon with anthropogenic sulfate and the associated enhancement of the absorption efficiency increases the atmospheric absorption in the source regions, despite the concurrent decrease of the BC load. The simulated net global annual mean effect of anthropogenic sulfate on atmospheric absorption of black carbon is negative with a value of - 0.2 W m^-2. Our findings have important implications for future emission scenarios and mitigation strategies as they show that variations in sulfate precursor emissions affect atmospheric absorption via microphysical interactions resulting in a spatially inhomogeneous response pattern.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 1029 Composition of aerosols and dust particles
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005