Retrieval of atmospheric CFC-11 and CFC-12 from high-resolution FTIR observations at Hefei and comparisons with other independent datasets
<p>Synthetic halogenated organic chlorofluorocarbons (CFCs) play an important role in stratospheric ozone depletion and contribute significantly to the greenhouse effect. In this work, the mid-infrared solar spectra measured by ground-based high-resolution Fourier transform infrared spectrosco...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-11-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/15/6739/2022/amt-15-6739-2022.pdf |
| Summary: | <p>Synthetic halogenated organic chlorofluorocarbons (CFCs) play an
important role in stratospheric ozone depletion and contribute significantly
to the greenhouse effect. In this work, the mid-infrared solar spectra
measured by ground-based high-resolution Fourier transform infrared
spectroscopy (FTIR) were used to retrieve atmospheric CFC-11 (CCl<span class="inline-formula"><sub>3</sub></span>F)
and CFC-12 (CCl<span class="inline-formula"><sub>2</sub></span>F<span class="inline-formula"><sub>2</sub></span>) at Hefei, China. The CFC-11 columns observed
from January 2017 to December 2020 and CFC-12 columns from September 2015 to
December 2020 show a similar annual decreasing trend and seasonal cycle,
with an annual rate of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.47</mn><mo>±</mo><mn mathvariant="normal">0.06</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="a806b63420daa298ff93df3a88ef1a58"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00001.svg" width="64pt" height="10pt" src="amt-15-6739-2022-ie00001.png"/></svg:svg></span></span> % yr<span class="inline-formula"><sup>−1</sup></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.68</mn><mo>±</mo><mn mathvariant="normal">0.03</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="05a558580ff3f283368b6ee9f0c86d63"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00002.svg" width="64pt" height="10pt" src="amt-15-6739-2022-ie00002.png"/></svg:svg></span></span> % yr<span class="inline-formula"><sup>−1</sup></span>, respectively. So the decline rate of CFC-11 is
significantly lower than that of CFC-12. CFC-11 total columns were higher in
summer, and CFC-12 total columns were higher in summer and autumn. Both
CFC-11 and CFC-12 total columns reached the lowest in spring. Further, FTIR
data of NDACC (Network for the Detection of Atmospheric Composition Change)
candidate station Hefei were compared with the ACE-FTS (Atmospheric Chemistry Experiment Fourier transform spectrometer) satellite data, WACCM
(Whole Atmosphere Community Climate Model) data, and the data from other
NDACC-IRWG (InfraRed Working Group) stations (St. Petersburg, Jungfraujoch, and Réunion). The
mean relative difference between the vertical profiles observed by FTIR and
ACE-FTS is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">5.6</mn><mo>±</mo><mn mathvariant="normal">3.3</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="a056c058674d3805ebe51300b5b3cb4c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00003.svg" width="52pt" height="10pt" src="amt-15-6739-2022-ie00003.png"/></svg:svg></span></span> % and <span class="inline-formula">4.8±0.9</span> % for CFC-11 and CFC-12 for an altitude of 5.5 to 17.5 km, respectively. The results demonstrate that our FTIR data agree relatively well with the ACE-FTS satellite data. The annual decreasing rate of CFC-11 measured from ACE-FTS and calculated by WACCM is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">1.15</mn><mo>±</mo><mn mathvariant="normal">0.22</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="292a4f5bd3790f82523c868d6a58eb39"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00004.svg" width="64pt" height="10pt" src="amt-15-6739-2022-ie00004.png"/></svg:svg></span></span> % yr<span class="inline-formula"><sup>−1</sup></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">1.68</mn><mo>±</mo><mn mathvariant="normal">0.18</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="fa5c9799570899d317ba42a3aa74e8e2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00005.svg" width="64pt" height="10pt" src="amt-15-6739-2022-ie00005.png"/></svg:svg></span></span> % yr<span class="inline-formula"><sup>−1</sup></span>, respectively. The interannual decreasing rates
of atmospheric CFC-11 obtained from ACE-FTS and WACCM data are higher than
that from FTIR observations. Also, the annual decreasing rate of CFC-12 from
ACE-FTS and WACCM is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.85</mn><mo>±</mo><mn mathvariant="normal">0.15</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="2294670ac25a512326edc7e3d1cf5ace"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00006.svg" width="64pt" height="10pt" src="amt-15-6739-2022-ie00006.png"/></svg:svg></span></span> % yr<span class="inline-formula"><sup>−1</sup></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.81</mn><mo>±</mo><mn mathvariant="normal">0.05</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="cc8aa34009771a0ee6ba2211bc2cb1d7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-6739-2022-ie00007.svg" width="64pt" height="10pt" src="amt-15-6739-2022-ie00007.png"/></svg:svg></span></span> % yr<span class="inline-formula"><sup>−1</sup></span>, respectively, close to the corresponding values from the FTIR measurements. The total columns of CFC-11 and CFC-12 at the Hefei and St. Petersburg stations are significantly higher than those at the Jungfraujoch and Réunion (Maïdo) stations, and the two values reached the maximum in local summer or autumn and the minimum in local spring or winter at the four stations. The seasonal variability at the three stations in the Northern Hemisphere is higher than that at the station in the Southern Hemisphere.</p> |
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| ISSN: | 1867-1381 1867-8548 |