Abstract
Abstract. Biogenic non-methane volatile organic compounds (NMVOCs) emitted from vegetation are a primary source for the chemical production of carbon monoxide (CO) in the atmosphere, and these biogenic emissions account for about 18 % of the global CO burden. Partitioning CO fluxes to different source types in top-down inversion methods is challenging; typically a simple scaling of the posterior flux to prior flux values for fossil fuel, biogenic and biomass burning sources is used. Here we show top-down estimates of biogenic CO fluxes using a Bayesian inference approach, which explicitly accounts for both posterior and a priori CO flux uncertainties. This approach re-partitions CO fluxes following inversion of Measurements Of Pollution In The Troposphere (MOPITT) CO observations with the GEOS-Chem model, a global chemical transport model driven by assimilated meteorology from the NASA Goddard Earth Observing System (GEOS). We compare these results to the prior information for CO used to represent biogenic NMVOCs from GEOS-Chem, which uses the Model of Emissions of Gases and Aerosols from Nature (MEGAN) for biogenic emissions. We evaluate the a posteriori biogenic CO fluxes against top-down estimates of isoprene fluxes using Ozone Monitoring Instrument (OMI) formaldehyde observations. We find similar seasonality and spatial consistency in the posterior CO and top-down isoprene estimates globally. For the African savanna region, both top-down CO and isoprene seasonality vary significantly from the MEGAN a priori inventory. This method for estimating biogenic sources of CO will provide an independent constraint on modeled biogenic emissions and has the potential for diagnosing decadal-scale changes in emissions due to land-use change and climate variability.
Highlights
Carbon monoxide (CO) plays a critical role in tropospheric chemistry and climate as a precursor to the greenhouse gases ozone (O3) and carbon dioxide (CO2) and through its influence on methane (CH4) lifetime via its destruction by the hydroxyl radical (OH) (e.g., IPCC AR5: IPCC, 2014; Gaubert et al, 2017)
Biogenic non-methane volatile organic compounds (NMVOCs) emitted from vegetation represent a significant source of precursors that oxidize and produce CO, accounting for around 18 % of the global CO budget (e.g., Folberth et al, 2006, Table 8, not including anthropogenic VOCs)
Previous efforts to estimate the amount of atmospheric CO that is produced chemically from biogenic NMVOC emissions have used Measurements Of Pollution In The Troposphere (MOPITT) (Measurements of Pollution in The Troposphere) satellite observations as a “top-down” constraint while estimating CO fluxes from different sectors such as fossil fuels, biomass burning and biogenic NMVOCs (Fortems-Cheiney et al, 2011; Hooghiemstra et al, 2011, 2012; Yin et al, 2015; Jiang et al, 2017)
Summary
Carbon monoxide (CO) plays a critical role in tropospheric chemistry and climate as a precursor to the greenhouse gases ozone (O3) and carbon dioxide (CO2) and through its influence on methane (CH4) lifetime via its destruction by the hydroxyl radical (OH) (e.g., IPCC AR5: IPCC, 2014; Gaubert et al, 2017). Previous efforts to estimate the amount of atmospheric CO that is produced chemically from biogenic NMVOC emissions have used MOPITT (Measurements of Pollution in The Troposphere) satellite observations as a “top-down” constraint while estimating CO fluxes from different sectors such as fossil fuels, biomass burning and biogenic NMVOCs (Fortems-Cheiney et al, 2011; Hooghiemstra et al, 2011, 2012; Yin et al, 2015; Jiang et al, 2017). These estimates have updated the prior fluxes in these sectors. The results presented here for CO from biogenic NMVOC sources give additional, independent information from global satellite observations that can be used to constrain biogenic emissions in areas that are not well monitored with other measurements
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