Dependence of solar radiative forcing of forest fire aerosol on ageing and state of mixture M. Fiebig1, A. Stohl2, M. Wendisch3, S. Eckhardt2, and A. Petzold1 1Deutsches Zentrum für Luft und Raumfahrt Oberpfaffenhofen, Institut für Physik der Atmosphäre, Wessling, Germany 2Technische Universität München, Lehrstuhl für Bioklimatologie und Immissionsforschung, Freising-Weihenstephan, Germany 3Leibniz-Institut für Troposphärenforschung, Leipzig, Germany
Abstract. During airborne in situ measurements of particle size distributions in a forest fire plume originating in Northern Canada,
an accumulation mode number mean diameter of 0.34 mm was observed over Lindenberg, Germany on 9 August 1998.
Realizing that this is possibly the largest value observed for this property in a forest fire plume, scenarios of
plume ageing by coagulation are considered to explain the observed size distribution, concluding that the plume
dilution was inhibited in parts of the plume. The uncertainties in coagulation rate and transition from external to internal mixture of absorbing forest fire
and non-absorbing background particles cause uncertainties in the plume's solar instantaneous radiative forcing of
20-40% and of a factor of 5-6, respectively. Including information compiled from other studies on this plume, it is concluded that the plume's characteristics are
qualitatively consistent with a radiative-convective mixed layer.
Citation: Fiebig, M., Stohl, A., Wendisch, M., Eckhardt, S., and Petzold, A.: Dependence of solar radiative forcing of forest fire aerosol on ageing and state of mixture, Atmos. Chem. Phys., 3, 881-891, doi:10.5194/acp-3-881-2003, 2003.