Chemistry and Physics Faculty Articles

Document Type

Article

Publication Date

7-16-2003

Publication Title

Journal of Geophysical Research: Atmospheres

Keywords

Gases, Particles, Biomass fires, Smoke, Savanna fires, Evolution of smoke

ISSN

2169-897X

Volume

108

Issue/No.

D13

First Page

SAF 21-1

Last Page

SAF 21-20

Abstract

Airborne measurements of particles and gases from a 1000-ha savanna fire in South Africa are presented. These measurements represent the most extensive data set reported on the aging of biomass smoke. The measurements include total concentrations of particles (CN), particle sizes, particulate organic carbon and black carbon, light-scattering coefficients, downwelling UV fluxes, and mixing ratios for 42 trace gases and 7 particulate species. The ratios of excess nitrate, ozone, and gaseous acetic acid to excess CO increased significantly as the smoke aged over ∼40–45 min, indicating that these species were formed by photochemistry in the plume. For 17 other species, the excess mixing ratio normalized by the excess mixing ratio of CO decreased significantly with smoke age. The relative rates of decrease for a number of chemical species imply that the average OH concentration in the plume was ∼1.7 × 107 molecules cm−3. Excess CN, normalized by excess CO, decreased rapidly during the first ∼5 min of aging, probably due to coagulation, and then increased, probably due to gas-to-particle conversion. The CO-normalized concentrations of particles <1.5 μm in diameter decreased, and particles >1.5 μm diameter increased, with smoke age. The spectral depletion of solar radiation by the smoke is depicted. The downwelling UV flux near the vertical center of the plume was about two-thirds of that near the top of the plume.

Comments

©2003 by the American Geophysical Union

Additional Comments

8485

DOI

10.1029/2002JD002352

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