Satellite observations of atmospheric HCFC-142b and the recent decline in its rate of increase

The presence of hydrochlorofluorocarbons (HCFCs) in the atmosphere is entirely the consequence of human activity. Over the past couple decades, HCFCs have been the "intermediate" refrigerants/foam-blowing agents used to replace CFCs as non-chlorinated alternatives are developed and phased in. The Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS) is the only space-based instrument that measures height resolved concentrations of multiple chlorine containing species, including HCFCs, in the upper troposphere - lower stratosphere (UTLS), and ACE-FTS has been doing so for the past 15 years. Due to the success of the Montreal Protocol, concentrations of atmospheric CFCs are on the decline, and as per the treaty, HCFCs are currently being phased out. This study analyzes the changes in concentrations of ACE-FTS HCFC-142b, and other chlorinated species, and preliminary results show that, in the UTLS, the rate of increase in HCFC-142b concentrations has started to decline. These results are in relatively good agreement with NOAA ground based measurements of HCFC-142b. Model simulations will also be performed to see if these can capture the HCFC-142b variations that the ACE-FTS data exhibit, given the concentrations measured at the surface.