Recent Decreases in the Growth Rate of Atmospheric HCFC‐22 Column Derived From the Ground‐Based FTIR Harmonized Retrievals at 16 NDACC Sites

Abstract

HCFC-22 is an ozone-depleting substance with a greenhouse effect. The atmospheric mole fractions of HCFC-22 have been increasing since the 1950s. Within the NDACC-IRWG network, HCFC-22 mol fractions can be retrieved from solar absorption spectra measured by ground-based FTIR. However, only a few sites have provided HCFC-22 data sets. Here, we demonstrate a harmonized FTIR HCFC-22 retrieval strategy and generate a new global NDACC-IRWG HCFC-22 data set at 16 FTIR sites. The systematic and random uncertainties are 5.3%–8.7% and 3.2%–8.0%, respectively. A maximum HCFC-22 column annual growth rate was observed in 2009 with a mean of 7.65 ± 1.39 ppt/year, and the HCFC-22 annual growth rate decreased to 3.57 ± 1.39 ppt/year (2016–2020) and 2.15 ± 2.09 ppt/year (2021–2023). The annual growth rates derived from the FTIR measurements are compared to the ones derived from NOAA surface flask samplings and ACE-FTS satellite measurements, and the three independent data sets show a good agreement.