ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-6669-2010 Vertical transport rates and concentrations of OH and Cl radicals in the Tropical Tropopause Layer from observations of CO<sub>2</sub> and halocarbons: implications for distributions of long- and short-lived chemical species Park S. 1 Atlas E. L. 2 Jiménez R. 1 Daube B. C. 1 Gottlieb E. W. 1 Nan J. 1 Jones D. B. A. 3 Pfister L. 4 Conway T. J. 5 Bui T. P. 4 Gao R.-S. 5 Wofsy S. C. 1 Dept. of Earth and Planetary Sciences and the School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, FL, USA Dept. of Physics, University of Toronto, Toronto, Ontario, Canada NASA, Ames Research Center, Moffett Field, CA, USA NOAA, Earth System Research Laboratory, Boulder, CO, USA 21 07 2010 10 14 6669 6684 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/10/6669/2010/acp-10-6669-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/6669/2010/acp-10-6669-2010.pdf

Rates for large-scale vertical transport of air in the Tropical Tropopause Layer (TTL) were determined using high-resolution, in situ observations of CO<sub>2</sub> concentrations in the tropical upper troposphere and lower stratosphere during the NASA Tropical Composition, Cloud and Climate Coupling (TC4) campaign in August 2007. Upward movement of trace gases in the deep tropics was notably slower in TC4 than during the Costa Rica AURA Validation Experiment (CR-AVE), in January 2006. Transport rates in the TTL were combined with in situ measurements of chlorinated and brominated organic compounds from whole air samples to determine chemical loss rates for reactive chemical species, providing empirical vertical profiles for 24-h mean concentrations of hydroxyl radicals (OH) and chlorine atoms in the TTL. The analysis shows that important short-lived species such as CHCl<sub>3</sub>, CH<sub>2</sub>Cl<sub>2</sub>, and CH<sub>2</sub>Br<sub>2</sub> have longer chemical lifetimes than the time for transit of the TTL, implying that these species, which are not included in most models, could readily reach the stratosphere and make significant contributions of chlorine and/or bromine to stratospheric loading.

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