Fractional release factors of long-lived halogenated organic compounds in the tropical stratosphere

Abstract

Abstract. Fractional release factors (FRFs) of organic trace gases are time-independent quantities that influence the calculation of Global Warming Potentials and Ozone Depletion Potentials. We present the first set of vertically resolved FRFs for 15 long-lived halocarbons in the tropical stratosphere up to 34 km altitude. They were calculated from measurements on air samples collected on board balloons and a high altitude aircraft. We compare the derived dependencies of FRFs on the mean stratospheric transit times (the socalled mean ages of air) with similarly derived FRFs originating from measurements at higher latitudes and find significant differences. Moreover a comparison with averaged FRFs currently used by the World Meteorological Organisation revealed the limitations of these measures due to their observed vertical and latitudinal variability. The presented data set could be used to improve future ozone level and climate projections.

Long-term tropospheric trend of octafluorocyclobutane (c-C<sub>4</sub>F<sub>8</sub> or PFC-318)

“…the mean stratospheric transport time of a given air parcel) by using a long-lived tracer which is growing in the atmosphere at a well defined rate. As recently described by Laube et al (2010b), the approach of Engel et al (2002) has been used to derive mean ages of the Geophysica samples based on concurrent measurements of SF 6 . The tropospheric trend of SF 6 was taken from the NOAA-ESRL records which were obtained from http://www.esrl.noaa.gov/gmd/ (updated from Geller et al, 1997).…”

Evidence for heterogeneous chlorine activation in the tropical UTLS

“…For TROCCINOX and SCOUT-O 3 , only the long-lived CFC-11 and CFC-12, with respective lifetimes of 45 and 100 years (WMO, 2006), were measured with adequate time resolution by the HAGAR in-situ gas chromatograph. The fractional release of chlorine from these two gases is small (<5%) for young air typically found in the tropical UTLS (Laube et al, 2010), with a much larger fraction of Cl y coming from CH 3 Cl, CCl 4 and very short lived species (VSLS) in these air masses (Laube et al, 2008).…”

Continued increase of CFC-113a (CCl&lt;sub&gt;3&lt;/sub&gt;CF&lt;sub&gt;3&lt;/sub&gt;) mixing ratios in the global atmosphere: emissions, occurrence and potential sources

“…Various pumps were used for the different sampling activities, all of which have been thoroughly tested for a large range of trace gases (Brenninkmeijer et al, 2007;Laube et al, 2010a;Allin et al, 2015 andOram et al, 2017). After collection, the samples were transported to the University of East Anglia (UEA) to be analysed on a high-sensitivity gas chromatograph coupled to a Waters AutoSpec magnetic sector mass spectrometer (GC-MS).…”