DOI

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 225pptv (parts per trillion by volume; CFC-11), 493pptv (CFC-12), and 238pptv (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 8-12km 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.

Original languageEnglish
Pages (from-to)5349–5368
Number of pages20
JournalAtmospheric Measurement Techniques
Volume14
Issue number8
DOIs
StatePublished - 4 Aug 2021

    Scopus subject areas

  • Environmental Science(all)

    Research areas

  • LONG-TERM TREND, HIGH-RESOLUTION, SPECTROSCOPIC MEASUREMENTS, CCL2F2 MEASUREMENTS, FTIR MEASUREMENTS, IN-SITU, ACE-FTS, RETRIEVAL, CCL3F, VALIDATION

ID: 84477897