Atmos. Chem. Phys. Discuss., 8, 12197-12225, 2008
© Author(s) 2008. This work is distributed
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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.
Mechanisms for synoptic transport of atmospheric CO2 in the midlatitudes and tropics
N. Parazoo1, A. Denning1, S. Kawa2, K. Corbin1, R. Lokupitiya1, and I. Baker1
1Atmospheric Science Department, Colorado State University, Fort Collins, Colorado, USA
2NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

Abstract. Synoptic variations of CO2 mixing ratio produced by interactions between weather and surface fluxes are investigated mechanistically and quantitatively in midlatitude and tropical regions using continuous in-situ CO2 observations in North America, South America and Europe and forward chemical transport model simulations with the Parameterized Chemistry Transport Model. Frontal CO2 climatologies show consistently strong, characteristic frontal CO2 signals throughout the midlatitudes of North America and Europe. Transitions between synoptically identifiable CO2 air masses or transient spikes along the frontal boundary typically characterize these signals. One case study of a summer cold front shows that CO2 gradients organize with deformational flow along weather fronts producing strong and spatially coherent variations. A boundary layer budget equation is constructed in order to determine contributions to boundary layer CO2 tendencies by horizontal and vertical advection, moist convection, and biological and anthropogenic surface fluxes. Analysis of this equation suggests that, in midlatitudes, advection is responsible for 50–90% of the amplitude of frontal variations in the summer, depending on upstream influences, and 50% of all day-to-day variations throughout the year. Simulations testing sensitivity to local cloud and surface fluxes further suggest that horizontal advection is a major source of CO2 variability in midlatitudes. In the tropics, coupling between convective transport and surface CO2 flux is most important. Due to the scarcity of tropical observations available at the time of this study, future work should extend such mechanistic analysis to additional tropical locations.

Citation: Parazoo, N., Denning, A., Kawa, S., Corbin, K., Lokupitiya, R., and Baker, I.: Mechanisms for synoptic transport of atmospheric CO2 in the midlatitudes and tropics, Atmos. Chem. Phys. Discuss., 8, 12197-12225, doi:10.5194/acpd-8-12197-2008, 2008.
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