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Atmos Chem Phys

Title:		Quantifying global terrestrial methanol emissions using observations from the TES satellite sensor
Author(s):		Wells KC; Millet DB; Cady-Pereira KE; Shephard MW; Henze DK; Bousserez N; Apel EC; de Gouw J; Warneke C; Singh HB;
Address:		"Department of Soil, Water, and Climate, University of Minnesota, St. Paul, Minnesota, USA. Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA. Environment Canada, Downsview, Ontario, Canada. Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado, USA. Atmospheric Chemistry Division, NCAR, Boulder, Colorado, USA. Earth System Research Laboratory, NOAA, Boulder, Colorado, USA. CIRES, University of Colorado, Boulder, Colorado, USA. NASA Ames Research Center, Moffett Field, California, USA"
Journal Title:		Atmos Chem Phys
Year:		2014
Volume:		20140313
Issue:		5
Page Number:		2555 - 2570
DOI:		10.5194/acp-14-2555-2014
ISSN/ISBN:		1680-7316 (Print) 1680-7324 (Electronic) 1680-7316 (Linking)
Abstract:		"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"
Keywords:
Notes:		"PubMed-not-MEDLINEWells, K C Millet, D B Cady-Pereira, K E Shephard, M W Henze, D K Bousserez, N Apel, E C de Gouw, J Warneke, C Singh, H B eng NNX10AG65G/NASA/NASA/ Germany 2014/03/01 Atmos Chem Phys. 2014 Mar; 14(5):2555-2570. doi: 10.5194/acp-14-2555-2014. Epub 2014 Mar 13"