Twenty years of global stratospheric fluorine inventories from Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements

We present fluorine inventories calculated for twenty years (2004–2023) and five latitude bands (82–60°N, 60–30°N, 30°N–30°S, 30–60°S, and 60–82°S) at altitudes from the surface up to 55 km. The inventories were calculated using the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) version 5.2 retrievals of the volume mixing ratios (VMRs) of 15 fluorine-containing species. Of these 15 species, 3 are product gases: HF, COF2, COClF, and 12 are source gases: SF6, PFC-14 (CF4), CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CClF2CCl2F), HCFC-22 (CHF2Cl), HCFC-141b (C2H3Cl2F), HCFC-142b (C2H3ClF2), HFC-23 (CHF3), HFC-32 (CH2F2), HFC-125 (C2HF5), and HFC-134a (C2H2F4). As necessary, ACE-FTS data was supplemented with data from the TOMCAT 3-D chemical transport model and ground-based measurements from the National Oceanic and Atmospheric Administration (NOAA) & the Advanced Global Atmospheric Gases Experiment (AGAGE). The total fluorine (Ftot) profiles are dominated by source gas contributions in the troposphere and lower stratosphere; up to 35 km in the tropics (30°N–30°S), 30 km in mid-latitudes (60–30°N/30–60°S), and 24 km near the poles (82–60°N/60–82°S). In this atmospheric region the primary contributions come from CFCs, HCFCs, carbon tetrafluoride (CF4), and increasingly in recent years HFCs. Above these altitudes HF increasingly dominates the Ftot profile, reaching as much as 79% of Ftot at 55 km. The 2004–2023 time series of the mean Ftot inventories shows a global increase of 48.9 ± 0.7 ppt/year or 1.68 ± 0.02 %/year resulting in a mean Ftot approaching 3.5 ppb in 2023.