ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-6037-2008 On interpreting studies of tracer transport by deep cumulus convection and its effects on atmospheric chemistry Lawrence M. G. 1 Salzmann M. 1 2 Max-Planck-Institut für Chemie, Mainz, Germany Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, New Jersey, USA 21 10 2008 8 20 6037 6050 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/8/6037/2008/acp-8-6037-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/6037/2008/acp-8-6037-2008.pdf

Global chemistry-transport models (CTMs) and chemistry-GCMs (CGCMs) generally simulate vertical tracer transport by deep convection separately from the advective transport by the mean winds, even though a component of the mean transport, for instance in the Hadley and Walker cells, occurs in deep convective updrafts. This split treatment of vertical transport has various implications for CTM simulations. In particular, it has led to a misinterpretation of several sensitivity simulations in previous studies in which the parameterized convective transport of one or more tracers is neglected. We describe this issue in terms of simulated fluxes and fractions of these fluxes representing various physical and non-physical processes. We then show that there is a significant overlap between the convective and large-scale mean advective vertical air mass fluxes in the CTM MATCH, and discuss the implications which this has for interpreting previous and future sensitivity simulations, as well as briefly noting other related implications such as numerical diffusion.

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