First HFC-134a retrievals from ground-based FTIR solar absorption spectra, comparison with TOMCAT model simulations, in-situ AGAGE observations, and ACE-FTS satellite data for the Jungfraujoch station

Abstract

Successive regulations on the production and consumption of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) have led to the use of hydrofluorocarbons (HFCs) as substitution products. Consequently, these potent greenhouse gases are now controlled under the Kigali Amendment (2016) to the Montreal Protocol. HFC-134a is the preferred substitute to CFC-12 as a refrigerant and is the most abundant HFC in the atmosphere today. This work presents the first retrievals from ground-based Fourier Transform InfraRed (FTIR) high-resolution solar absorption spectra, recorded at the Jungfraujoch station as part of the Network for the Detection of Atmospheric Composition Change (NDACC). To verify these retrievals, the FTIR time series was compared to three other datasets: a simulation of the TOMCAT 3-D chemical transport model, the Fourier Transform Spectrometer on board the Atmospheric Chemistry Experiment (ACE-FTS) L2 v5.2 retrievals, and the Jungfraujoch in-situ surface observations conducted within the Advanced Global Atmospheric Gases Experiment (AGAGE) network. The overall trends of HFC-134a (2004–2022) were analyzed to assess the relative growth rates of this atmospheric compound. These trends are 7.34 ± 0.16 %/year (FTIR), 7.12 ± 0.05 %/year (TOMCAT), 7.29 ± 0.16 %/year (ACE-FTS), and 6.61 ± 0.05 %/year (in-situ). The relative trends are in good agreement, so these novel FTIR retrievals are validated. Consequently, this strategy could be implemented at other NDACC sites to achieve a quasi-global detection of this species using the FTIR remote sensing technique.