Reactive Carbon Species from Biomass Burning Activities During SAFARI 2000: Implications for Tropospheric HOx Budgets.

Considerable convection occurs in regions of biomass burning, resulting in vast quantities of reactive species being transported high into the troposphere. During this convective activity large amounts of water vapour are also lifted out of the boundary layer. These processes result in large perturbations to the normal clean air chemistry which is dominated by methane and carbon monoxide. In situ measurements of a range of trace species were made during a series of flights during SAFARI 2000 on the UKMO C-130 aircraft. Whole air samples were also collected for non-methane hydrocarbons (NMHC) analysis. During one flight a polluted layer was observed off the coast of Namibia, this layer showed considerable enhancements in many species emitted during biomass burning. During a subsequent flight a large fire was encountered and studied for a considerable distance. Changes in ratios between species during the fresh and aged plumes indicated considerable photochemical activity during transport. In particular observations in aged plumes indicate a considerable fraction of acetone present was produced photochemically following emission. Simple modelling studies have been run and the results compared.