Stratospheric lifetimes of CFC-12, CCl<sub>4</sub>, CH<sub>4</sub>, CH<sub>3</sub>Cl and N<sub>2</sub>O from measurements made by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS)
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...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2013-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/13/6921/2013/acp-13-6921-2013.pdf |
| Summary: | 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, CCl<sub>4</sub>, CH<sub>4</sub>, CH<sub>3</sub>Cl and N<sub>2</sub>O. 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 <i>Geophysica</i> 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 (CCl<sub>4</sub>), 69 + (−) 65 (23) yr (CH<sub>3</sub>Cl), 123 + (−) 53 (28) yr (N<sub>2</sub>O) and 195 + (−) 75 (42) yr (CH<sub>4</sub>). 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 N<sub>2</sub>O, 195 + (−) 139 (57) for CH<sub>4</sub>, 35 + (−) 14 (8) for CCl<sub>4</sub> and 69 + (−) 2119 (34) yr for CH<sub>3</sub>Cl. For CH<sub>3</sub>Cl & CH<sub>4</sub> this represents the first calculation of the stratospheric lifetime using data from a space based instrument. |
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| ISSN: | 1680-7316 1680-7324 |