Abstract
Abstract. Fluorine-containing species can be extremely effective atmospheric greenhouse gases. We present fluorine budgets using organic and inorganic species retrieved by the ACE-FTS satellite instrument supplemented with output from the SLIMCAT 3-D chemical transport model. The budgets are calculated between 2004 and 2009 for a number of latitude bands: 70–30° N, 30–00° N, 00° N–30° S, and 30–70° S. At lower altitudes total fluorine profiles are dominated by the contribution from CFC-12, up to an altitude of 20 km in the extra-tropics and 29 km in the tropics; above these altitudes the profiles are dominated by hydrogen fluoride (HF). Our data show that total fluorine profiles at all locations have a negative slope with altitude, providing evidence that overall fluorine emissions (measured by their F content) have been increasing with time. Total stratospheric fluorine is increasing at a similar rate in the tropics: 32.5 ± 4.9 ppt yr−1 (1.31 ± 0.20% per year) in the Northern Hemisphere (NH) and 29.8 ± 5.3 ppt yr−1 (1.21 ± 0.22% per year) in the Southern Hemisphere (SH). Extra-tropical total stratospheric fluorine is also increasing at a similar rate in both the NH and SH: 28.3 ± 2.7 ppt per year (1.12 ± 0.11% per year) in the NH and 24.3 ± 3.1 ppt per year (0.96 ± 0.12% per year) in the SH. The calculation of radiative efficiency-weighted total fluorine allows the changes in radiative forcing between 2004 and 2009 to be calculated. These results show an increase in radiative forcing of between 0.23 ± 0.11% per year and 0.45 ± 0.11% per year, due to the increase in fluorine-containing species during this time. The decreasing trends in the mixing ratios of halons and chlorofluorocarbons (CFCs), due to their prohibition under the Montreal Protocol, have suppressed an increase in total fluorine caused by increasing mixing ratios of hydrofluorocarbons (HFCs). This has reduced the impact of fluorine-containing species on global warming.
Highlights
Many fluorine-containing chemicals are widely used in industry and elsewhere because they are chemically inert, nontoxic and odourless
This paper presents fluorine budgets calculated from Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-Fourier Transform Spectrometer (FTS)) measurements supplemented with output from the SLIMCAT 3-D chemical transport model (CTM)
Atmospheric Chemistry Experiment (ACE)-FTS retrievals were again compared once more to HALOE, these results showed that ACE-FTS retrievals were larger by between 5–20 % (Mahieu et al, 2008)
Summary
Many fluorine-containing chemicals are widely used in industry and elsewhere because they are chemically inert, nontoxic and odourless. The most recent fluorine budget was carried out using data from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) (Nassar et al, 2006b) This budget used version 2.2 ACE-FTS retrievals of CF4, CFC-11, CFC-12, CFC-113, COClF, COF2, HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HF and SF6. Previous studies from ACE data from this period have shown that the rate of decrease in the VMRs of CFC-11, CFC-12 and CFC-113 is significantly smaller than the rate of increase in the VMRs of the three most common HCFCs, HCFC-22, HCFC-141b and HCFC-142b (Brown et al, 2011) The effect that these changes in the atmospheric VMRs of particular species will have on the total fluorine budget will be dependent on the number of fluorine atoms contained by each species.
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