Ground-based measurements of HF and HCl total columns in atmosphere near Saint Petersburg (2009–2023)

Abstract

ABSTRACT Monitoring of the ozonosphere requires observing the concentration of gases involved in the formation and depletion processes of stratospheric ozone. This study focuses on optimization the ground-based Fourier transform infrared (FTIR) method of retrieving total columns of halogen-containing gases hydrogen chloride (HCl) and hydrogen fluoride (HF). The work describes generally the procedure for selecting parameters to update the technique for deriving their atmospheric contents. Using parameters of the optimized methods, we obtained temporal variability of daily mean values of HCl and HF total columns above St. Petersburg from March 2009 to March 2023 by ground-based measurements of direct solar radiation spectra with a Bruker IFS 125 HR (IR Fourier spectrometer). The linear trends amount to (0.59 ± 0.27) %/year and (−0.26 ± 0.21) %/year for HF and HCl, respectively. The seasonal variability of both gases content was also calculated. The peak of HF total column occurred in March, while the low was observed in November. April showed the maximum of HCl content annually, and the lowest HCl total column appeared in the mid-winter. The results were compared with datasets from the nearest NDACC sites Harestua and Kiruna. Trends and seasonal cycles at the sites are consistent. The analysis of the variability of HCl to HF contents ratio demonstrated the time periods of decrease in HCl content caused by the chemical activity in the stratosphere. Finally, we analysed the ozone layer state over St. Petersburg at the beginning of 2023 using ground-based FTIR-measurements of HCl and HF total columns and satellite measurements of ozone total columns.