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Short‐wave radiative effects of biomass burning aerosol during SAFARI2000
Author(s) -
Osborne Simon R.,
Haywood James M.,
Francis Peter N.,
Dubovik Oleg
Publication year - 2004
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.03.134
Subject(s) - aerosol , downwelling , radiative transfer , environmental science , plume , atmospheric sciences , radiance , extinction (optical mineralogy) , single scattering albedo , radiative flux , optical depth , remote sensing , meteorology , upwelling , geology , physics , optics , mineralogy , oceanography
We present data from two case‐studies during the Southern AFricAn Research Initiative (SAFARI2000) of the radiative effects of a biomass burning plume advecting over the ocean. In situ aircraft measurements were made of the aerosol vertical structure, the aerosol microphysics, and the aerosol optical properties (scattering and absorption coefficients). Remote sensing measurements of the upwelling broadband short‐wave (SW) radiative fluxes (0.3–3.0µm) were made above the plume. Together with modelling of the clear‐air flux using a flexible radiation scheme, we have been able to determine the local mean direct radiative effects of the aerosol column for the two cases. Aerosol optical depths were derived using a number of techniques: the upwelling fluxes, vertical integration of the in situ extinction coefficient, and using downwelling sky radiances. These optical depths are compared and discussed; discrepancies are revealed through instrument sampling problems and horizontal inhomogeneity of the aerosol. Spectrally resolved downwelling SW sky radiances as a function of scattering angle were measured and modelled. The modelling technique illustrates the importance of including unpolluted marine boundary‐layer aerosol as part of the aerosol column. A retrieval algorithm that uses the measured downwelling sky radiances as input has also been utilized. This algorithm derives a columnar aerosol size distribution for comparison against the measured biomass burning and marine boundary‐layer size distributions. The retrieved columnar size distribution is acceptable in representing the atmospheric aerosol in terms of describing the effect on scattered radiances. © Crown copyright, 2004. Royal Meteorological Society