Geographic and seasonal distributions of CO transport pathways and their roles in determining CO centers in the upper troposphere 1Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USA
30 May 2012
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Received: 19 Oct 2011 – Published in Atmos. Chem. Phys. Discuss.: 09 Dec 2011Abstract. Past studies have identified a variety of pathways by which carbon monoxide
(CO) may be transported from the surface to the tropical upper troposphere
(UT); however, the relative roles that these transport pathways play in
determining the distribution and seasonality of CO in the tropical UT remain
unclear. We have developed a method to automate the identification of two
pathways ("local convection" and "advection within the lower troposphere
(LT) followed by convective vertical transport") involved in CO transport
from the surface to the UT. This method is based on the joint application of
instantaneous along-track, co-located, A-Train satellite measurements. Using
this method, we find that the locations and seasonality of the UT CO maxima
in the tropics were strongly correlated with the frequency of local
convective transport during 2007. We also find that the "local convection"
pathway (convective transport that occurred within a fire region) typically
transported significantly more CO to the UT than the "LT advection →
convection" pathway (advection of CO within the LT from a fire region to a
convective region prior to convective transport). To leading order, the
seasonality of CO concentrations in the tropical UT reflected the
seasonality of the "local convection" transport pathway during 2007. The
UT CO maxima occurred over Central Africa during boreal spring and over
South America during austral spring. Occurrence of the "local convection"
transport pathway in these two regions also peaked during these seasons.
During boreal winter and summer, surface CO emission and convection were
located in opposite hemispheres, which limited the effectiveness of
transport to the UT. During these seasons, CO transport from the surface to
the UT typically occurred via the "LT advection → convection"
Revised: 08 May 2012 – Accepted: 08 May 2012 – Published: 30 May 2012
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., 12, 4683-4698, doi:10.5194/acp-12-4683-2012, 2012.