Twenty years of global stratospheric fluorine inventories from
Atmospheric Chemistry Experiment Fourier Transform Spectrometer
(ACE-FTS) measurements
Abstract
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 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). 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
chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon
tetrafluoride (CF4), and increasingly in recent years hydrofluorocarbons
(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 1.6% per
year, suggesting that the Ftot VMR is increasing with time.