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| Titel |
The 2007–2011 evolution of tropical methane in the mid-troposphere as seen from space by MetOp-A/IASI |
| VerfasserIn |
C. Crevoisier, D. Nobileau, R. Armante, L. Crépeau, T. Machida, Y. Sawa, H. Matsueda, T. Schuck, T. Thonat, J. Pernin, N. A. Scott, A. Chédin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 8 ; Nr. 13, no. 8 (2013-04-25), S.4279-4289 |
| Datensatznummer |
250018607
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| Publikation (Nr.) |
 copernicus.org/acp-13-4279-2013.pdf |
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| Zusammenfassung |
| Since July 2007, monthly averages of mid-tropospheric methane have been
retrieved in the tropics over land and sea, by day and night, from IASI
onboard MetOp-A, yielding a complete view of the geographical distribution,
seasonality and long-term tendency of methane in the mid-troposphere.
Retrieved methane displays a clear seasonal cycle of ~25 ppbv in the
northern tropics, with a maximum in November and a minimum in April–May, a
more complex cycle of ~15 ppbv in the southern tropics, and a
south-to-north latitudinal variation of ~30 ppbv – in good agreement
with regular aircraft measurements of the CONTRAIL program. Comparisons with
CARIBIC aircraft measurements made at ~11 km yield an averaged
difference between collocated IASI estimates and CARIBIC measurements of
7.2 ppbv with a standard deviation of 13.1 ppbv. Comparisons with aircraft
measurements made above 6 km during five HIPPO campaigns give an averaged
difference between collocated IASI estimates and HIPPO measurements of
5.1 ppbv with a standard deviation of 16.3 ppbv. These comparisons show
that IASI captures well the evolution of mid-tropospheric methane. In
particular, in 2007 and 2008, IASI shows an increase of mid-tropospheric
methane in the tropical region of 9.5 ± 2.8 and
6.3 ± 1.7 ppbv yr−1, respectively – in excellent agreement with
the rate of increase measured at the surface after almost a decade of
near-zero growth. IASI also indicates a slowing down of this increase in the
following years to ~2 ppbv yr−1, with the highest increase in
2010. Assuming that the recent evolution of methane is mostly due to an
increase in surface emissions, IASI might indicate a decrease in tropical
wetland emissions for the period 2009–2011 compared to 2007–2008, in
agreement with decreasing tropical precipitation over this period, together
with an increase in biomass burning emissions in 2010 in the southern
tropics. |
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