Abstract
Abstract. We used the GEOS-Chem model and its adjoint to quantify Chinese non-methane volatile organic compound (NMVOC) emissions for the year 2007, using the tropospheric column concentrations of formaldehyde and glyoxal observed by the Global Ozone Monitoring Experiment 2A (GOME-2A) instrument and the Ozone Monitoring Instrument (OMI) as quantitative constraints. We conducted a series of inversion experiments using different combinations of satellite observations to explore their impacts on the top-down emission estimates. Our top-down estimates for Chinese annual total NMVOC emissions were 30.7 to 49.5 (average 41.9) Tg yr−1, including 16.4 to 23.6 (average 20.2) Tg yr−1 from anthropogenic sources, 12.2 to 22.8 (average 19.2) Tg yr−1 from biogenic sources, and 2.08 to 3.13 (average 2.48) Tg yr−1 from biomass burning. In comparison, the a priori estimate for Chinese annual total NMVOC emissions was 38.3 Tg yr−1, including 18.8 Tg yr−1 from anthropogenic sources, 17.3 Tg yr−1 from biogenic sources, and 2.27 Tg yr−1 from biomass burning. The simultaneous use of glyoxal and formaldehyde observations helped distinguish the NMVOC species from different sources and was essential in constraining anthropogenic emissions. Our four inversion experiments consistently showed that the Chinese anthropogenic emissions of NMVOC precursors of glyoxal were larger than the a priori estimates. Our top-down estimates for Chinese annual emission of anthropogenic aromatics (benzene, toluene, and xylene) ranged from 5.5 to 7.9 Tg yr−1, 2 % to 46 % larger than the estimate of the a priori emission inventory (5.4 Tg yr−1). Three out of our four inversion experiments indicated that the seasonal variation in Chinese NMVOC emissions was significantly stronger than indicated in the a priori inventory. Model simulations driven by the average of our top-down NMVOC emission estimates (which had a stronger seasonal variation than the a priori) showed that surface afternoon ozone concentrations over eastern China increased by 1–8 ppb in June and decreased by 1–10 ppb in December relative to the simulations using the a priori emissions and were in better agreement with measurements. We concluded that the satellite observations of formaldehyde and glyoxal together provided quantitative constraints on the emissions and source types of NMVOCs over China and improved our understanding on regional chemistry.
Highlights
Non-methane volatile organic compounds (NMVOCs) are emitted into the atmosphere from surface anthropogenic, biogenic, and biomass burning sources
These findings offered some support for using the Global Ozone Monitoring Experiment (GOME)-2A formaldehyde vertical column densities (VCDs) scaled by 1.7 as an upperbound constraint for Chinese NMVOC emissions
The a priori NMVOC emission estimates from biogenic, anthropogenic, and biomass burning sources were taken from the inventories developed by Guenther et al (2006), Li et al (2014, 2017), and Huang et al (2012), respectively, as well as van der Werf et al (2010)
Summary
Non-methane volatile organic compounds (NMVOCs) are emitted into the atmosphere from surface anthropogenic, biogenic, and biomass burning sources. Fu et al (2007) analyzed the spatial and seasonal variation in the formaldehyde column observations from the Global Ozone Monitoring Experiment (GOME) over East and South Asia They showed that, during the early 2000s, Chinese reactive NMVOC fluxes from biogenic, anthropogenic, and biomass burning sources were 3, 1.2, and 8.8 times their respective bottom-up estimates at that time. Stavrakou et al (2009a) pioneered a two-compound inversion using tropospheric glyoxal and formaldehyde column observations from the Scanning Imaging Absorption spectrometer for Atmospheric CHartographY (SCIAMACHY) satellite instrument to constrain the global sources of glyoxal They estimated that the anthropogenic NMVOC fluxes over East Asia for the year 2005 were a factor of 2 to 3 larger than the bottom-up estimates of the Emission Database for Global Atmospheric Research (EDGAR, v3.3) inventory (Olivier et al, 2001, 2002) and the REanalysis TROpospheric (RETRO) emission inventory (Schultz et al, 2007). We examined the impacts of our top-down NMVOC emission estimates on surface air quality over China
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