The influence of biomass burning on tropospheric composition over the tropical Atlantic Ocean and Equatorial Africa during the West African monsoon in 2006

The long range transport and chemical processing of such emissions thus has the potential to exert a dominant influence on the composition of the tropical troposphere over Equatorial Africa (EA) and the Tropical Atlantic Ocean (TAO). We have performed simulations using a three-dimensional global chemistry-transport model (CTM) to quantify the effect that continental transport of such BB plumes has on the EA region.

BB emissions from southern Africa were found to exert a significant influence over the TAO and EA between 10° S - 20° N. The maximum concentrations in CO and O₃ occur between 0 - 5° S near the position of the African Easterly Jet - South as placed by the European Centre for Medium range Weather Forecasts (ECMWF) meteorological analysis data. By comparing co-located model output with in-situ measurements we show that the CTM fails to capture the tropospheric profile of CO in southern Africa near the main source region of the BB emissions, as well as the "extreme" concentrations of both CO and O₃ seen between 600-700 hPa over EA around 6° N. For more northerly locations the model exhibits high background concentrations in both CO and O₃ related to BB emissions from southern Africa.