1Department of Physics, University of York, Heslington, YO10 5DD, UK
2Department of Physics, University of Wuppertal, 42119 Wuppertal, Germany
3Science and Technology Corporation, Lanham, Maryland, 20706, USA
4Department of Chemistry, University of Waterloo, Ontario, Canada
5Department of Chemistry and Biochemistry, Old Dominion University, Virginia, USA
6Department of Chemistry, University of York, Heslington, YO10 5DD, UK
Received: 24 Jan 2013 – Discussion started: 14 Feb 2013
Abstract. Long lived halogen-containing compounds are important atmospheric constituents since they can act both as a source of chlorine radicals, which go on to catalyse ozone loss, and as powerful greenhouse gases. The long-term impact of these species on the ozone layer is dependent on their stratospheric lifetimes. Using observations from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) we present calculations of the stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O. The lifetimes were calculated using the slope of the tracer–tracer correlation of these species with CFC-11 at the tropopause. The correlation slopes were corrected for the changing atmospheric concentrations of each species based on age of air and CFC-11 measurements from samples taken aboard the Geophysica aircraft – along with the effective linear trend of the volume mixing ratio (VMR) from tropical ground based AGAGE (Advanced Global Atmospheric Gases Experiment) sites. Stratospheric lifetimes were calculated using a CFC-11 lifetime of 45 yr. These calculations produced values of 113 + (−) 26 (18) yr (CFC-12), 35 + (−) 11 (7) yr (CCl4), 69 + (−) 65 (23) yr (CH3Cl), 123 + (−) 53 (28) yr (N2O) and 195 + (−) 75 (42) yr (CH4). The errors on these values are the weighted 1σ non-systematic errors. Systematic errors were estimated by recalculating lifetimes using VMRs which had been modified to reflect differences between ACE-FTS retrieved VMRs and those from other instruments. The results of these calculations, including systematic errors, were as follows: 113 + (−) 32 (20) for CFC-12, 123 + (−) 83 (35) for N2O, 195 + (−) 139 (57) for CH4, 35 + (−) 14 (8) for CCl4 and 69 + (−) 2119 (34) yr for CH3Cl. For CH3Cl & CH4 this represents the first calculation of the stratospheric lifetime using data from a space based instrument.
Revised: 05 Jun 2013 – Accepted: 17 Jun 2013 – Published: 23 Jul 2013
Brown, A. T., Volk, C. M., Schoeberl, M. R., Boone, C. D., and Bernath, P. F.: Stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O from measurements made by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), Atmos. Chem. Phys., 13, 6921-6950, doi:10.5194/acp-13-6921-2013, 2013.