Atmos. Chem. Phys. Discuss., 11, 32423-32453, 2011
www.atmos-chem-phys-discuss.net/11/32423/2011/
doi:10.5194/acpd-11-32423-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Geographic and seasonal distributions of CO transport pathways and their roles in determining CO centers in the upper troposphere
L. Huang1, R. Fu1, J. H. Jiang2, J. S. Wright1, and M. Luo2
1Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USA
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Abstract. Past studies have identified various pathways along which carbon monoxide (CO) in the tropical upper troposphere (UT) may have been transported from the surface. However, the roles that these transport pathways play in determining the locations and seasonality of CO in the tropical UT remain unclear. In particular, UT CO peaks during the spring and fall seasons when surface CO emission and deep atmospheric convection are moderate relative to those observed during winter and summer. We have developed a method to automate the identification of three pathways that transport CO to the UT, which makes joint use of several A-Train satellite measurements. We use this method to show that the locations and seasonality of the major UT CO centers in the tropics during 2007 were largely determined by local convective transport. On average, the "local convection" pathway, in which convection occurred within a fire region, transported significantly more CO to the UT than the "LT advection → convection" pathway, in which CO was advected within the lower troposphere from a fire region to a convective region prior to convection. To leading order, the seasonality of CO concentrations in the tropical UT followed the seasonality of the "local convection" transport pathway. The centers of highest CO peaked over Central Africa during boreal spring and over South America during austral spring, when the "local convection" transport pathway was most prevalent. During boreal winter and summer, surface CO emission and convection were located in opposite hemispheres, limiting the effectiveness of transport to the UT. In these seasons, CO was mainly transported to the UT via the "LT advection → convection" pathway, in which CO was advected within the lower troposphere from fire source regions in the winter hemisphere to convective regions in the summer hemisphere, or via the "UT advection" pathway, in which UT CO was redistributed from the summer hemisphere to the winter hemisphere.

Citation: Huang, L., Fu, R., Jiang, J. H., Wright, J. S., and Luo, M.: Geographic and seasonal distributions of CO transport pathways and their roles in determining CO centers in the upper troposphere, Atmos. Chem. Phys. Discuss., 11, 32423-32453, doi:10.5194/acpd-11-32423-2011, 2011.
 
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