Parikhit Sinha

Evolution of gases and particles from a savanna fire in South Africa

average OH concentration in the plume was � 1.7 � 10 7 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 mm 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. INDEX TERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 3374 Meteorology and Atmospheric Dynamics: Tropical meteorology; KEYWORDS: gases, particles, biomass fires, smoke, savanna fires, evolution of smoke