Effect of biomass burning on surface ozone: A case study in 2010 over Northern Sub-Saharan Africa (NSSA)

Abstract:

One of the major sources of tropospheric ozone (O₃) precursors such as nitrogen oxides (NO_x), carbon monoxides (CO), and non-methane volatile organic compounds (NMVOCs) is biomass burning. The emissions from the burning do not only affect air quality and climate locally, but also on a continental to hemispheric scales through long-range transport. We have used NASA’s Global Modeling Initiative Chemistry and Transport Model (GMI-CTM), to quantify the changes in surface ozone over Northern Sub-Saharan Africa (NSSA: 0 – 20N, 20W – 55E), as triggered by biomass burning from different regions.

During the winter months (e.g. January), most of the burning is concentrated in the NSSA region while in summer it shifts southward outside the NSSA region. Our analysis reveals that out of the total contribution to surface ozone from biomass burning emissions in the NSSA region, 92 % is due to NSSA biomass burning while the remaining 8 % is from outside the NSSA. In fact, most (~75 %) of the 8 % comes from outside the African continent because little to no biomass burning occurs in Africa outside of the NSSA region during this time of year. However, during the summer months (e.g. July), most of the contribution to NSSA surface ozone (96 %) is due to burning from outside NSSA. Only 10 % of the 96 % comes from outside the African continent because during this time most of the burning is from outside the NSSA but within the African continent. In spring (e.g. April) approximately equal percentages of contributions come from within and outside the NSSA region.