Abstract
Abstract. Chlorofluorocarbons (CFCs) play a key role in stratospheric ozone loss and are strong infrared absorbers that contribute to global warming. The stratospheric lifetimes of CFCs are a measure of their stratospheric loss rates that are needed to determine global warming and ozone depletion potentials. We applied the tracer–tracer correlation approach to zonal mean climatologies from satellite measurements and model data to assess the lifetimes of CFCl3 (CFC-11) and CF2Cl2 (CFC-12). We present estimates of the CFC-11/CFC-12 lifetime ratio and the absolute lifetime of CFC-12, based on a reference lifetime of 52 years for CFC-11. We analyzed climatologies from three satellite missions, the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), the HIgh Resolution Dynamics Limb Sounder (HIRDLS), and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). We found a CFC-11/CFC-12 lifetime ratio of 0.47±0.08 and a CFC-12 lifetime of 112(96–133) years for ACE-FTS, a ratio of 0.46±0.07 and a lifetime of 113(97–134) years for HIRDLS, and a ratio of 0.46±0.08 and a lifetime of 114(98–136) years for MIPAS. The error-weighted, combined CFC-11/CFC-12 lifetime ratio is 0.46±0.04 and the CFC-12 lifetime estimate is 113(103–124) years. These results agree with the recent Stratosphere-troposphere Processes And their Role in Climate (SPARC) reassessment, which recommends lifetimes of 52(43–67) years and 102(88–122) years, respectively. Having smaller uncertainties than the results from other recent studies, our estimates can help to better constrain CFC-11 and CFC-12 lifetime recommendations in future scientific studies and assessments. Furthermore, the satellite observations were used to validate first simulation results from a new coupled model system, which integrates a Lagrangian chemistry transport model into a climate model. For the coupled model we found a CFC-11/CFC-12 lifetime ratio of 0.48±0.07 and a CFC-12 lifetime of 110(95–129) years, based on a 10-year perpetual run. Closely reproducing the satellite observations, the new model system will likely become a useful tool to assess the impact of advective transport, mixing, and photochemistry as well as climatological variability on the stratospheric lifetimes of long-lived tracers.
Highlights
Monitoring the global distributions of chlorofluorocarbons (CFCs) is important for various reasons
We present our estimates of the stratospheric lifetime ratio of CFC-11 and CFC-12 and the absolute lifetime of CFC-12 for the three satellite missions and the model
We here did not take the uncertainty of the CFC-11 reference lifetime into account when we estimated the error of the CFC-12 lifetime
Summary
Monitoring the global distributions of chlorofluorocarbons (CFCs) is important for various reasons. The chlorine released by photolytic decomposition of CFCs plays a key role in ozone depletion both in the upper stratosphere and in the polar regions (Molina and Rowland, 1974; Solomon, 1999). Tracer–tracer relations of long-lived trace gases, such as CFCs, are frequently examined to study dynamical processes in the stratosphere, in particular the mixing of air masses near the subtropical and polar vortex transport barriers (Volk et al, 1996; Waugh, 1997; Plumb et al, 2000; Müller et al, 2001; Morgenstern et al, 2002). Continuous, global measurements of CFCs are useful assets to validate the representation of transport, mixing, and photochemistry in atmospheric models (Eyring et al, 2005; Rind et al, 2007; Hoppe et al, 2014). We focus on CFCl3 (CFC-11) and CF2Cl2 (CFC-12), which are the CFCs with the largest atmospheric abundances
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