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| Titel |
First long-term observations of SF6 and N2O in the extra-tropical tropopause region |
| VerfasserIn |
Tanja Schuck, Carl Brenninkmeijer, Andreas Zahn, Peter van Velthoven |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048217
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| Zusammenfassung |
| Sulfur hexafluoride (SF6) and nitrous oxide (N2O) are greenhouse gases with continuously
increasing atmospheric mixing ratios. While SF6 is an entirely industrial gas, N2O is emitted
from both natural and anthropogenic sources, including the use of fertilizers. Several
monitoring networks have included SF6 and N2O in their measurement program, and
time-series of atmospheric observations reach back to the 1970s, but have been restricted to
ground-based measurements.
In 1997, the CARIBIC project (Civil Aircraft for the Regular Investigation of the
Atmosphere Based on an Instrument Container, www.caribic-atmospheric.com) started to
provide regular aircraft based observations of various atmospheric constituents. Once per
month an instrumented air freight container is deployed during flights of a passenger aircraft.
Besides a wide range of high resolution measurements being performed in-flight, whole air
samples are collected and analyzed for greenhouse gases, including SF6 and N2O. At cruise
altitudes between 9 and 12.5 km the aircraft frequently crosses the tropopause, and in the
extra-tropics about 40% of the flight time is spent in the transition layer above the
tropopause. SF6 and N2O both only have sinks in the stratosphere and therefore exhibit
pronounced gradients across the tropopause. This in combination with their continuous
increase makes them ideal indicators of stratospheric air. Especially SF6 with its long
atmospheric lifetime of ~ 3200 years has frequently been used as a tracer for atmospheric
transport.
The CARIBIC record represents the first long-term time-series of regular SF6 and N2O
measurements in the upper troposphere and lowermost stratosphere, covering the periods
1998–2002 and 2006–present. Focusing on the northern hemisphere mid-latitudes we will
present upper tropospheric trends in SF6 and N2O mixing ratios, and we will also analyze
gradients across the extra-tropical tropopause. |
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