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High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the southeast US

Kaiser, Jennifer and Jacob, Daniel J. and Zhu, Lei and Travis, Katherine R. and Fisher, Jenny A. and Abad, Gonzalo González and Zhang, Lin and Zhang, Xuesong and Fried, Alan and Crounse, John D. and St. Clair, Jason M. and Wisthaler, Armin (2018) High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the southeast US. Atmospheric Chemistry and Physics, 18 (8). pp. 5483-5497. ISSN 1680-7324. doi:10.5194/acp-18-5483-2018.

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Isoprene emissions from vegetation have a large effect on atmospheric chemistry and air quality. Bottom-up isoprene emission inventories used in atmospheric models are based on limited vegetation information and uncertain land cover data, leading to potentially large errors. Satellite observations of atmospheric formaldehyde (HCHO), a high-yield isoprene oxidation product, provide top-down information to evaluate isoprene emission inventories through inverse analyses. Past inverse analyses have however been hampered by uncertainty in the HCHO satellite data, uncertainty in the time- and NO_x-dependent yield of HCHO from isoprene oxidation, and coarse resolution of the atmospheric models used for the inversion. Here we demonstrate the ability to use HCHO satellite data from OMI in a high-resolution inversion to constrain isoprene emissions on ecosystem-relevant scales. The inversion uses the adjoint of the GEOS-Chem chemical transport model at 0.25° × 0.3125° horizontal resolution to interpret observations over the southeast US in August–September 2013. It takes advantage of concurrent NASA SEAC4RS aircraft observations of isoprene and its oxidation products including HCHO to validate the OMI HCHO data over the region, test the GEOS-Chem isoprene oxidation mechanism and NO_x environment, and independently evaluate the inversion. This evaluation shows in particular that local model errors in NOx concentrations propagate to biases in inferring isoprene emissions from HCHO data. It is thus essential to correct model NO_x biases, which was done here using SEAC^4RS observations but can be done more generally using satellite NO_2 data concurrently with HCHO. We find in our inversion that isoprene emissions from the widely used MEGAN v2.1 inventory are biased high over the southeast US by 40 % on average, although the broad-scale distributions are correct including maximum emissions in Arkansas/Louisiana and high base emission factors in the oak-covered Ozarks of southeast Missouri. A particularly large discrepancy is in the Edwards Plateau of central Texas where MEGAN v2.1 is too high by a factor of 3, possibly reflecting errors in land cover. The lower isoprene emissions inferred from our inversion, when implemented into GEOS-Chem, decrease surface ozone over the southeast US by 1–3 ppb and decrease the isoprene contribution to organic aerosol from 40 to 20 %.

Item Type:Article
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URLURL TypeDescription
Jacob, Daniel J.0000-0002-6373-3100
Travis, Katherine R.0000-0003-1628-0353
Abad, Gonzalo González0000-0002-8090-6480
Crounse, John D.0000-0001-5443-729X
St. Clair, Jason M.0000-0002-9367-5749
Additional Information:© Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 06 Dec 2017 – Discussion started: 19 Dec 2017. Revised: 03 Apr 2018 – Accepted: 10 Apr 2018 – Published: 23 Apr 2018. We are grateful for the contributions from all members of the SEAC^4RS flight and science teams. We acknowledge Thomas B. Ryerson for his contribution of the NO_x measurements. Tomas Mikoviny is acknowledged for his support with the PTR-MS data acquisition and analysis. PTR-MS measurements during SEAC^4RS were supported by the Austrian Federal Ministry for Transport, Innovation and Technology (bmvit) through the Austrian Space Applications Programme (ASAP) of the Austrian Research Promotion Agency (FFG). Funding was provided by the NASA Aura Science Team.
Funding AgencyGrant Number
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)UNSPECIFIED
Österreichische Forschungsförderungsgesellschaft (FFG)UNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:20180509-092250734
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Official Citation:Kaiser, J., Jacob, D. J., Zhu, L., Travis, K. R., Fisher, J. A., González Abad, G., Zhang, L., Zhang, X., Fried, A., Crounse, J. D., St. Clair, J. M., and Wisthaler, A.: High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the southeast US, Atmos. Chem. Phys., 18, 5483-5497,, 2018
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86306
Deposited By: Tony Diaz
Deposited On:09 May 2018 16:45
Last Modified:15 Nov 2021 20:37

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