Atmos. Chem. Phys. Discuss., 10, 453-489, 2010
www.atmos-chem-phys-discuss.net/10/453/2010/
doi:10.5194/acpd-10-453-2010
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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.
Atmospheric transport of persistent semi-volatile organic chemicals to the Arctic and cold condensation at the mid-troposphere – Part 1: 2-D modeling in mean atmosphere
J. Ma
Air Quality Research Division, Environment Canada. 4905 Dufferin Street, Toronto, Ontario M3H 5T4, Canada

Abstract. In the first part of this study for revisiting the cold condensation effect on global distribution of semi-volatile organic chemicals (SVOCs), the atmospheric transport of SVOCs to the Arctic at the mid-troposphere in a mean meridional atmospheric circulation over Northern Hemisphere was simulated by a two-dimensional atmospheric transport model. Results show that under the mean meridional atmosphere the long-range atmospheric transport of SVOCs from warm latitudes to the Arctic occurs primarily at the mid-troposphere. Accordingly, the cold condensation of the chemicals is likely also to take place at the mid-troposphere over a source region of the chemicals in warm low latitudes. We demonstrate that the temperature dependent vapour pressure and atmospheric degradation rate of SVOCs exhibit similarities between lower atmosphere over the Arctic and the mid-troposphere over a tropical region. Frequent occurrence of atmospheric ascending motion and convection over warm latitudes carry the chemicals to a higher altitude where some of these chemicals may condense/partition to particle or aqueous phase through the interaction with atmospheric aerosols, cloud water droplets and ice particles, and become more persistence in the lower temperatures. Stronger winds at the mid-troposphere then convey the condensed chemicals to the Arctic where they are brought down to the surface by large-scale descending motion and wet deposition. Using calculated water droplet-air partitioning coefficient of several persistent organic semi-volatile chemicals under a mean air temperature profile from the equator to the North Pole we propose that clouds are likely important sorbing media for SVOCs and pathway of the cold condensation effect and poleward atmospheric transport. The role of deposition and atmospheric descending motion in the cold condensation effect over the Arctic was also discussed.

Citation: Ma, J.: Atmospheric transport of persistent semi-volatile organic chemicals to the Arctic and cold condensation at the mid-troposphere – Part 1: 2-D modeling in mean atmosphere, Atmos. Chem. Phys. Discuss., 10, 453-489, doi:10.5194/acpd-10-453-2010, 2010.
 
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