5:15 PM - 6:45 PM
[AAS09-P22] Observation and analysis of HFC-134a with a ground-based FTIR in Tsukuba, Japan
Keywords:ozone destruction, FTIR, freon, HFC, SFIT4
After the discovery of the ozone hole in Antarctica in 1980s, it was discovered that artificial refrigerants which contain CFCs (Chloro-Fluoro-Carbons) is the cause of Antarctic ozone destruction. Consequently, the Vienna Convention for the Protection of the Ozone Layer, and the Montreal Protocol on Substances that Deplete the Ozone Layer were adopted in March 1985 and in September 1987, respectively. The use of CFCs has been substituted by HCFCs (Hydro-Chloro-Fluoro-Carbons), and further by HFCs (Hydro-Fluoro-Carbons). CFCs has already banned in all countries by 2010, and the production and consumption of HCFCs has also banned in developed countries by 2020. Now, HFCs is mainly used for refrigerants and foaming agents, and atmospheric amount of HFCs has been increasing recently. Among them, HFC-134a (CH2FCF3) is the most abundant HFCs, which has atmospheric lifetime of 14 years and has 100-year Global Warming Potential of 1470. We tried to retrieve atmospheric amount of HFC-134a from ground-based FTIR spectra taken at Tsukuba.
In this analysis, spectrum fitting tool of SFIT4 Ver. 1.0.18 was used. For the analysis of HFC-134a, two spectral windows of 1104-1106 cm-1 and 1182-1187 cm-1 in MCT detector region were used. Pseudo line list of HFC-134a produced by one of the co-author G. C. Toon was used for fitting line parameter. For other gases, HITRAN-2000 and ATM-2000 line parameters were used. Initial profile of HFC-134a was taken from 2018 ACE-FTS L2 v4.0 data (Harrison et al., 2021). We analyzed Tsukuba FTIR data from 2014 to 2023.
Figure 1 shows trend of analyzed HFC-134a with two fitting procedures, i.e., Tikhonov regularization method and Optimal Estimation Method (OEM). HFC-134a has a peak in spring and a bottom in fall. This annual variation may reflect the change in tropopause heights. The increase rate in Tsukuba between 2018 and 2023 are +5.9 %/y by Tikhonov, and +5.3 %/y by OEM method, respectively. These trends are comparable or a bit larger than the trends of FTIR (+4.65 %/y), TOMCAT CTM (+4.42 %/y), or ACE-FTS satellite measurement (+4.81 %/y) at Jungfraujoch, Switzerland. We will analyze the HFC-134a from FTIR spectra taken at Syowa Station, or at Rikubetsu, Japan to compare the difference in hemispheres in future.
In this analysis, spectrum fitting tool of SFIT4 Ver. 1.0.18 was used. For the analysis of HFC-134a, two spectral windows of 1104-1106 cm-1 and 1182-1187 cm-1 in MCT detector region were used. Pseudo line list of HFC-134a produced by one of the co-author G. C. Toon was used for fitting line parameter. For other gases, HITRAN-2000 and ATM-2000 line parameters were used. Initial profile of HFC-134a was taken from 2018 ACE-FTS L2 v4.0 data (Harrison et al., 2021). We analyzed Tsukuba FTIR data from 2014 to 2023.
Figure 1 shows trend of analyzed HFC-134a with two fitting procedures, i.e., Tikhonov regularization method and Optimal Estimation Method (OEM). HFC-134a has a peak in spring and a bottom in fall. This annual variation may reflect the change in tropopause heights. The increase rate in Tsukuba between 2018 and 2023 are +5.9 %/y by Tikhonov, and +5.3 %/y by OEM method, respectively. These trends are comparable or a bit larger than the trends of FTIR (+4.65 %/y), TOMCAT CTM (+4.42 %/y), or ACE-FTS satellite measurement (+4.81 %/y) at Jungfraujoch, Switzerland. We will analyze the HFC-134a from FTIR spectra taken at Syowa Station, or at Rikubetsu, Japan to compare the difference in hemispheres in future.