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| Titel |
Quantifying global terrestrial methanol emissions using observations from the TES satellite sensor |
| VerfasserIn |
K. C. Wells, D. B. Millet, K. E. Cady-Pereira, M. W. Shephard, D. K. Henze, N. Bousserez, E. C. Apel, J. de Gouw, C. Warneke, H. B. Singh |
| 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. 5 ; Nr. 14, no. 5 (2014-03-13), S.2555-2570 |
| Datensatznummer |
250118477
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| Publikation (Nr.) |
 copernicus.org/acp-14-2555-2014.pdf |
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| Zusammenfassung |
| We employ new global space-based measurements of atmospheric methanol from
the Tropospheric Emission Spectrometer (TES) with the adjoint of
the GEOS-Chem chemical transport model to quantify terrestrial emissions of
methanol to the atmosphere. Biogenic methanol emissions in the model are
based on version 2.1 of the Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1), using leaf area data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and GEOS-5
assimilated meteorological fields. We first carry out a pseudo observation
test to validate the overall approach, and find that the TES sampling
density is sufficient to accurately quantify regional- to continental-scale
methanol emissions using this method. A global inversion of two years of TES
data yields an optimized annual global surface flux of 122 Tg yr−1
(including biogenic, pyrogenic, and anthropogenic sources), an increase of
60% from the a priori global flux of 76 Tg yr−1. Global terrestrial
methanol emissions are thus nearly 25% those of isoprene (~540 Tg yr−1),
and are comparable to the combined emissions of all anthropogenic
volatile organic compounds (~100–200 Tg yr−1). Our a posteriori
terrestrial methanol source leads to a strong improvement of the simulation
relative to an ensemble of airborne observations, and corroborates two other
recent top-down estimates (114–120 Tg yr−1) derived using in situ and
space-based measurements. Inversions testing the sensitivity of optimized
fluxes to model errors in OH, dry deposition, and oceanic uptake of
methanol, as well as to the assumed a priori constraint, lead to global
fluxes ranging from 118 to 126 Tg yr−1. The TES data imply a relatively
modest revision of model emissions over most of the tropics, but a
significant upward revision in midlatitudes, particularly over Europe and
North America. We interpret the inversion results in terms of specific
source types using the methanol : CO correlations measured by TES, and find
that biogenic emissions are overestimated relative to biomass burning and
anthropogenic emissions in central Africa and southeastern China, while they
are underestimated in regions such as Brazil and the US. Based on our
optimized emissions, methanol accounts for > 25% of the
photochemical source of CO and HCHO over many parts of the northern
extratropics during springtime, and contributes ~6% of the
global secondary source of those compounds annually. |
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