ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-9791-2012 Tropical convective transport and the Walker circulation Hosking J. S. 1 3 Russo M. R. 1 2 Braesicke P. 1 2 Pyle J. A. 1 2 Centre for Atmospheric Science, University of Cambridge, Cambridge, UK National Centre for Atmospheric Science, University of Cambridge, Cambridge, UK now at: British Antarctic Survey, Cambridge, UK 29 10 2012 12 20 9791 9797 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/12/9791/2012/acp-12-9791-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/9791/2012/acp-12-9791-2012.pdf

We introduce a methodology to visualise rapid vertical and zonal tropical transport pathways. Using prescribed sea-surface temperatures in four monthly model integrations for 2005, we characterise preferred transport routes from the troposphere to the stratosphere in a high resolution climate model. Most efficient transport is modelled over the Maritime Continent (MC) in November and February, i.e., boreal winter. In these months, the ascending branch of the Walker Circulation over the MC is formed in conjunction with strong deep convection, allowing fast transport into the stratosphere. In the model the upper tropospheric zonal winds associated with the Walker Circulation are also greatest in these months in agreement with ERA-Interim reanalysis data. We conclude that the Walker circulation plays an important role in the seasonality of fast tropical transport from the lower and middle troposphere to the upper troposphere and so impacts at the same time the potential supply of surface emissions to the tropical tropopause layer (TTL) and subsequently to the stratosphere.

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