Measurements of CFC-11, CFC-12, and HCFC-22 total columns in the atmosphere at the St. Petersburg site in 2009–2019

Alexander Polyakov,Anatoly Poberovsky,Yuri Timofeyev,Yana Virolainen,Maria Makarova,Anastasiia Nikulina

doi:10.5194/amt-14-5349-2021

Abstract

Abstract. Monitoring atmospheric anthropogenic halocarbons plays an important role in tracking their atmospheric concentrations in accordance with international agreements on emissions of ozone-depleting substances and, thus, in estimating the ozone layer recovery. Within the Network for the Detection of Atmospheric Composition Change (NDACC), regular Fourier transform infrared (FTIR) measurements can provide information on the abundancies of halocarbons on a global scale. We improved retrieval strategies for deriving the CFC-11 (CCl3F), CFC-12 (CCl2F2), and HCFC-22 (CHClF2) atmospheric columns from IR solar radiation spectra measured by the Bruker IFS125HR spectrometer at the St. Petersburg site (Russia). We used the Tikhonov–Phillips regularization approach for solving the inverse problem with optimized values of regularization parameters. We tested the strategies developed by comparison of the FTIR measurements with independent data. The analysis of the time series of column-averaged dry air mole fractions (Xgas) measured in 2009–2019 gives mean values of 225 pptv (parts per trillion by volume; CFC-11), 493 pptv (CFC-12), and 238 pptv (HCFC-22). Trend values total −0.40 % yr−1 (CFC-11), −0.49 % yr−1 (CFC-12), and 2.12 % yr−1 (HCFC-22). We compared the means, trends, and seasonal variability in XCFC-11, XCFC-12, and XHCFC-22 to that of (1) near-ground volume mixing ratios (VMRs), measured at the observational site Mace Head, Ireland (GVMR), (2) the mean in the 8–12 km layer VMRs, measured by ACE-FTS and averaged over 55–65∘ N latitudes (SVMR), and (3) Xgas values of the Whole Atmosphere Community Climate Model (WACCM) for the St. Petersburg site (WXgas). In general, the comparison of Xgas with the independent data showed a good agreement of their means within the systematic errors of the measurements considered. The trends observed over the St. Petersburg site demonstrate the smaller decrease rates for XCFC-11 and XCFC-12 than that of the independent data and the same increase rate for XHCFC-22. As a whole, Xgas, SVMR, and WXgas showed qualitatively similar seasonal variations, while the GVMR variability is significantly less, and only the WXHCFC-22 variations are essentially smaller than that of XHCFC-22 and SVMRHCFC-22.

Highlights

Since the middle of the 20th century, anthropogenic trace gases, the molecules of which contain halogens, due to their specific physical and chemical properties, have been actively used in the climatic and refrigeration industry, as well as in various propellants. Molina and Rowland (1974) have shown that these gases play an important role in the destruction of stratospheric ozone
The photolysis of CCl3F and CCl2F2 in the stratosphere leads to the appearance of active chlorine, which is involved in ozone depletion reactions
The techniques described above were applied to processing the entire archive of spectral measurements at the NDACC site of St

Summary

Introduction

Since the middle of the 20th century, anthropogenic trace gases, the molecules of which contain halogens, due to their specific physical and chemical properties, have been actively used in the climatic and refrigeration industry, as well as in various propellants. Molina and Rowland (1974) have shown that these gases play an important role in the destruction of stratospheric ozone. Since the middle of the 20th century, anthropogenic trace gases, the molecules of which contain halogens, due to their specific physical and chemical properties, have been actively used in the climatic and refrigeration industry, as well as in various propellants. The photolysis of CCl3F (trichlorofluoromethane; CFC-11) and CCl2F2 (dichlorodifluoromethane; CFC-12) in the stratosphere leads to the appearance of active chlorine, which is involved in ozone depletion reactions. The WMO (2018, Appendix A) estimates the ozone depletion potential (ODP) of CFC-12 as being 0.73– 0.81 (the ODP of CFC-11, chosen as a reference, equals 1). The major content of these gases is concentrated in the troposphere, in the equatorial region, the global circulation moves them out into the lower and middle stratosphere and transports them to high-latitude regions.

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Results

Conclusion