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
Author:
Park S.,Atlas E. L.,Jiménez R.,Daube B. C.,Gottlieb E. W.,Nan J.,Jones D. B. A.,Pfister L.,Conway T. J.,Bui T. P.,Gao R.-S.,Wofsy S. C.
Abstract
Abstract. Rates for large-scale vertical transport of air in the Tropical Tropopause Layer (TTL) were determined using high-resolution, in situ observations of CO2 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 CHCl3, CH2Cl2, and CH2Br2 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.
Publisher
Copernicus GmbH
Reference37 articles.
1. Andrews, A. E., Boering, K. A., Daube, B. C., Wofsy, S. C., Hintsa, E. J., Weinstock, E. M., and Bui, T. P.: Empirical age spectra for the lower tropical stratosphere from in situ observations of CO2: Implications for stratospheric transport, J. Geophys. Res., 104(D21), 26581–26596, 1999. 2. Andrews, A. E., Boering, K. A., Daube, B. C., Wofsy, S. C., Loewenstein, M., Jost, H., Podolske, J. R., Webster, C. R., Herman, R. L., Scott, D. C., Flesch, G. J., Moyer, E. J., Elkins, J. W., Dutton, G. S., Hurst, D. F., Moore, F. L., Ray, E. A., Romashkin, P. A., and Strahan, S. E.: Mean ages of stratospheric air derived from in situ observations of CO2, CH4, and N2O, J. Geophys. Res., 106(D23), 32295–32314, 2001a. 3. Andrews, A. E., Boering, K. A., Wofsy, S. C., Daube, B. C., Jones, D. B., Alex, S., Loewenstein, M., Podolske, J. R., and Strahan, S. E.: Empirical age spectra for the midlatitude lower stratosphere from in situ observations of CO2: Quantitative evidence for a subtropical "barrier" to horizontal transport, J. Geophys. Res., 106(D10), 10257–10274, 2001b. 4. Boering, K. A., Dessler, A. E., Loewenstein, M., McCormick, M. P., Podolske, J. R., Weinstock, E. M., and Yue, G. K.: Measurements of stratospheric carbon dioxide and water vapor at northern midlatitudes: Implications for troposphere-to-stratosphere transport, Geophys. Res. Lett., 22(20), 2737–2740, 1995. 5. Boering, K. A., Wofsy, S. C., Daube, B. C., Schneider, H. R., Loewenstein, M., and Podolske, J. R.: Stratospheric mean ages and transport rates from observations of carbon dioxide and nitrous oxide, Science, 274(5291), 1340–1343, 1996.
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