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RISS 인기검색어
- 검색키워드
- 저자 : Christopher Chan Miller (검색결과 4 건)
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Chan Miller, Christopher,Jacob, Daniel J.,Marais, Eloise A.,Yu, Karen,Travis, Katherine R.,Kim, Patrick S.,Fisher, Jenny A.,Zhu, Lei,Wolfe, Glenn M.,Hanisco, Thomas F.,Keutsch, Frank N.,Kaiser, Jennif Copernicus GmbH 2017 Atmospheric Chemistry and Physics Vol.17 No.14
<P>Abstract. Glyoxal (CHOCHO) is produced in the atmosphere by the oxidation of volatile organic compounds (VOCs). Like formaldehyde (HCHO), another VOC oxidation product, it is measurable from space by solar backscatter. Isoprene emitted by vegetation is the dominant source of CHOCHO and HCHO in most of the world. We use aircraft observations of CHOCHO and HCHO from the SENEX campaign over the southeast US in summer 2013 to better understand the CHOCHO time-dependent yield from isoprene oxidation, its dependence on nitrogen oxides (NOx ≡ NO + NO2), the behavior of the CHOCHO-HCHO relationship, the quality of OMI CHOCHO satellite observations, and the implications for using CHOCHO observations from space as constraints on isoprene emissions. We simulate the SENEX and OMI observations with the Goddard Earth Observing System chemical transport model (GEOS-Chem) featuring a new chemical mechanism for CHOCHO formation from isoprene. The mechanism includes prompt CHOCHO formation under low-NOx conditions following the isomerization of the isoprene peroxy radical (ISOPO2). The SENEX observations provide support for this prompt CHOCHO formation pathway, and are generally consistent with the GEOS-Chem mechanism. Boundary layer CHOCHO and HCHO are strongly correlated in the observations and the model, with some departure under low-NOx conditions due to prompt CHOCHO formation. SENEX vertical profiles indicate a free-tropospheric CHOCHO background that is absent from the model. The OMI CHOCHO data provide some support for this free-tropospheric background and show southeast US enhancements consistent with the isoprene source but a factor of 2 too low. Part of this OMI bias is due to excessive surface reflectivities assumed in the retrieval. The OMI CHOCHO and HCHO seasonal data over the southeast US are tightly correlated and provide redundant proxies of isoprene emissions. Higher temporal resolution in future geostationary satellite observations may enable detection of the prompt CHOCHO production under low-NOx conditions apparent in the SENEX data. </P>
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Cao, Hansen,Fu, Tzung-May,Zhang, Lin,Henze, Daven K.,Miller, Christopher Chan,Lerot, Christophe,Abad, Gonzalo Gonzá,lez,De Smedt, Isabelle,Zhang, Qiang,van Roozendael, Michel,Hendrick, Fran&cced Copernicus GmbH 2018 Atmospheric Chemistry and Physics Vol.18 No.20
<P><p><strong>Abstract.</strong> 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<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span>, including 16.4 to 23.6 (average 20.2) Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span> from anthropogenic sources, 12.2 to 22.8 (average 19.2) Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span> from biogenic sources, and 2.08 to 3.13 (average 2.48) Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span> from biomass burning. In comparison, the a priori estimate for Chinese annual total NMVOC emissions was 38.3<span class='thinspace'></span>Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span>, including 18.8<span class='thinspace'></span>Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span> from anthropogenic sources, 17.3<span class='thinspace'></span>Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span> from biogenic sources, and 2.27<span class='thinspace'></span>Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span> 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<span class='thinspace'></span>Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup></span>, 2<span class='thinspace'></span>% to 46<span class='thinspace'></span>% larger than the estimate of the a priori emission inventory (5.4<span class='thinspace'></span>Tg<span class='thinspace'></span>yr<span class='inline-formula'><sup>−1</sup>)</span>. 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<span class='thinspace'></span>ppb in June and decreased by 1-10<span class='thinspace'></span>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.</p> </P>
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