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Trend of lower stratospheric methane (CH4) from atmospheric chemistry experiment (ACE) and atmospheric trace molecule spectroscopy (ATMOS) measurements |
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| Authors: | Curtis P Rinsland Linda Chiou Emmanuel Mahieu |
| Institution: | a NASA Langley Research Center, Hampton, VA, USA b Science Systems and Applications, Inc., Hampton, VA, USA c Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 d Department of Chemistry, University of York, Heslington, York YO10 5DD, UK e Institute of Astrophysics and Geophysics, University of Liège, Allée du 6 Août, 17, B-4000 Liège, Belgium |
| Abstract: | The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985-2008 time period by combining spaceborne solar occultation measurements recorded with high spectral resolution Fourier transform spectrometers (FTSs). Volume mixing ratio (VMR) FTS measurements from the ATMOS (atmospheric trace molecule spectroscopy) FTS covering 120-10 hPa (∼16-30 km altitude) at 25°N-35°N latitude from 1985 and 1994 have been combined with Atmospheric Chemistry Experiment (ACE) SCISAT-1 FTS measurements covering the same latitude and pressure range from 2004 to 2008. The CH4 trend was estimated by referencing the VMRs to those measured for the long-lived constituent N2O to account for the dynamic history of the sampled airmasses. The combined measurement set shows that the VMR increase measured by ATMOS has been replaced by a leveling off during the ACE measurement time period. Our conclusion is consistent with both remote sensing and in situ measurements of the CH4 trend obtained over the same time span. |
| Keywords: | Methane Remote sensing Atmospheric chemistry Composition Trends |
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