Photochemistry of the African troposphere: Influence of biomass-burning emissions

The relative importance of biomass-burning (pyrogenic) emissions from savan nas, deforestation, agricultural waste burning, and biofuel consumption to tropospheric ozone abundance over Africa has been estimated for the year 19 93, on the basis of global model calculations. We also calculated the impor tance of this emission source to tropospheric ozone in other regions of the world and compared it to different sources on the African regional and glo bal scales. The estimated annual average total tropospheric ozone abundance over Africa for the reference year is 26 Tg. Pyrogenic, industrial, biogen ic, and lightning emissions account for 16, 19, 12, and 27%, respectively, while stratospheric ozone input accounts for 26%. In the planetary boundary layer over Africa, the contribution by biomass burning is similar to 24%. A large fraction of the African biomass-burning-related ozone is transporte d away from the continent. On a global scale, biomass burning contributes s imilar to 9% to tropospheric ozone. Our model calculations suggest that Afr ica is the single most important region for biomass-burning-related troposp heric ozone, accounting for similar to 35% of the global annual pyrogenic o zone enhancement of 29 Tg in 1993.