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Tropospheric transport differences between models using the same large-scale...

Orbe, C., D. Waugh, H. Yang, J. Lamarque, S. Tilmes, and D. Kinnison (2016), Tropospheric transport differences between models using the same large-scale meteorological fields, Geophys. Res. Lett., 44, doi:10.1002/2016GL071339.

The transport of chemicals is a major uncertainty in the modeling of tropospheric composition. A common approach is to transport gases using the winds from meteorological analyses, either using them directly in a chemical transport model or by constraining the flow in a general circulation model. Here we compare the transport of idealized tracers in several different models that use the same meteorological fields taken from Modern-Era Retrospective analysis for Research and Applications (MERRA). We show that, even though the models use the same meteorological fields, there are substantial differences in their global-scale tropospheric transport related to large differences in parameterized convection between the simulations. Furthermore, we find that the transport differences between simulations constrained with the same-large scale flow are larger than differences between free-running simulations, which have differing large-scale flow but much more similar convective mass fluxes. Our results indicate that more attention needs to be paid to convective parameterizations in order to understand large-scale tropospheric transport in models, particularly in simulations constrained with analyzed winds.

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Atmospheric Composition Modeling and Analysis Program (ACMAP)