Global Chemistry simulations in the AMMA-Model Intercomparison project

Here we present results obtained during the chemistry-transport modelling (CTM) component of the AMMA Multi-model Intercomparison Project (AMMA-MIP) using the recently developed L3JRCv2 emission dataset for Africa, where we place emphasis on the summer of 2006. With the use of passive tracers we show that the application of different parameterizations to describe both advection, vertical diffusion and convective mixing in a suite of state-of-the-art Global CTM’s results in significantly different transport mechanisms westwards of the African Continent. Moreover, we identify that the atmospheric composition over the Southern Atlantic is governed by air masses originating from southern Africa for this period resulting in maximal concentrations around 5°S. Comparisons with ozonesondes measurements at Cotonou (6.2°N, 2.2°E) indicate that the models generally over predict surface ozone and under predict ozone in the upper troposphere. Moreover, using recent aircraft measurements we show that the high ozone concentrations which occur around 700hPa around 5°N are not captured by any of the models indicating shortcomings in either the description of transport, the magnitude and/or location of emissions or the in-situ chemical ozone production by the various chemical mechanisms employed.