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| Titel |
Impact of the Asian monsoon anticyclone on the variability of mid-to-upper tropospheric methane above the Mediterranean Basin |
| VerfasserIn |
P. Ricaud, B. Sič, L. El Amraoui, J.-L. Attié, R. Zbinden, P. Huszar, S. Szopa, J. Parmentier, N. Jaidan, M. Michou, R. Abida, F. Carminati, D. Hauglustaine, T. August, J. Warner, R. Imasu, N. Saitoh, V.-H. Peuch |
| 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 ; 14, no. 20 ; Nr. 14, no. 20 (2014-10-29), S.11427-11446 |
| Datensatznummer |
250119129
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| Publikation (Nr.) |
 copernicus.org/acp-14-11427-2014.pdf |
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| Zusammenfassung |
| The space and time variabilities of methane (CH4) total column and upper
tropospheric mixing ratios are analysed above the Mediterranean Basin (MB) as
part of the Chemical and Aerosol Mediterranean Experiment (ChArMEx)
programme. Since the analysis of the mid-to-upper tropospheric CH4
distribution from spaceborne sensors and model outputs is challenging, we
have adopted a climatological approach and have used a wide variety of
data sets. We have combined spaceborne measurements from the Thermal And Near
infrared Sensor for carbon Observations – Fourier Transform Spectrometer
(TANSO-FTS) instrument on the Greenhouse gases Observing SATellite (GOSAT)
satellite, the Atmospheric InfraRed Spectrometer (AIRS) on the AURA platform
and the Infrared Atmospheric Sounder Interferometer (IASI) instrument aboard
the MetOp-A platform with model results from the Chemical Transport Model
(CTM) MOCAGE, and the Chemical Climate Models (CCMs) CNRM-AOCCM and
LMDz-OR-INCA (according to different emission scenarios). In order to
minimize systematic errors in the spaceborne measurements, we have only
considered maritime pixels over the MB. The period of interest spans from
2008 to 2011 considering satellite and MOCAGE data and, regarding the CCMs,
from 2001 to 2010. Although CH4 is a long-lived tracer with lifetime of
~12 years and is supposed to be well mixed in the troposphere, an
east–west gradient in CH4 is observed and modelled in the mid-to-upper
troposphere with a maximum in the Western MB in all seasons except in summer
when CH4 accumulates above the Eastern MB. The peak-to-peak amplitude of
the east–west seasonal variation in CH4 above the MB in the upper
troposphere (300 hPa) is weak but almost twice as great in the satellite
measurements (~25 ppbv) as in the model data (~15 ppbv).
The maximum of CH4 in summer above the eastern MB can be explained by a
series of dynamical processes only occurring in summer. The Asian monsoon
traps and uplifts high amounts of CH4 to the upper troposphere where
they build up. The Asian Monsoon Anticyclone redistributes these elevated
CH4 amounts towards North Africa and the Middle East to finally reach and
descend in the eastern MB. In the lower troposphere, the CH4 variability
is mainly driven by the local sources of emission in the vicinity of the MB. |
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