title: New observational constraints for atmospheric hydroxyl on global and hemispheric scales
abstract: Dramatic declines in emissions of methyl chloroform (1,1, 1-trichloroethane) resulting from the Montreal Protocol provide an unprecedented opportunity to improve our understanding of the oxidizing power of Earth's atmosphere. Atmospheric observations of this industrial gas during the late 1990s yield new insights into the global burden and distribution of the hydroxyl radical. Our results set firm upper limits on the global and Southern Hemispheric lifetimes of methyl chloroform and confirm the predominance of hydroxyl in the tropics. Our analysis suggests a global lifetime for methyl chloroform of 5.2 (+0.2, -0.3) years, a Southern Hemispheric lifetime of 4.9 (+0.2, -0.3) years, and mean annual concentrations of OH that are 15 +/- 10% higher south of the intertropical convergence zone than those north of this natural mixing boundary between the hemispheres.
authors.affiliation: National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80303, USA. Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard Univ.
authors.initials: SA
authors.lastname: Montzka
authors.initials: CM
authors.lastname: Spivakovsky
authors.initials: JH
authors.lastname: Butler
authors.initials: JW
authors.lastname: Elkins
authors.initials: LT
authors.lastname: Lock
authors.initials: DJ
authors.lastname: Mondeel