Constraining Emissions of Volatile Organic Compounds Over the Indian Subcontinent Using Space-Based Formaldehyde Measurements

Sreelekha Chaliyakunnel, Dylan B. Millet, Xin Chen

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

India is an air pollution mortality hot spot, but regional emissions are poorly understood. We present a high-resolution nested chemical transport model (GEOS-Chem) simulation for the Indian subcontinent and use it to interpret formaldehyde (HCHO) observations from two satellite sensors (OMI and GOME-2A) in terms of constraints on regional volatile organic compound (VOC) emissions. We find modeled biogenic VOC emissions to be overestimated by ~30–60% for most locations and seasons, and derive a best estimate biogenic flux of 16 Tg C/year subcontinent-wide for year 2009. Terrestrial vegetation provides approximately half the total VOC flux in our base-case inversions (full uncertainty range: 44–65%). This differs from prior understanding, in which biogenic emissions represent >70% of the total. Our derived anthropogenic VOC emissions increase slightly (13–16% in the base case, for a subcontinent total of 15 Tg C/year in 2009) over RETRO year 2000 values, with some larger regional discrepancies. The optimized anthropogenic emissions agree well with the more recent CEDS inventory, both subcontinent-wide (within 2%) and regionally. An exception is the Indo-Gangetic Plain, where we find an underestimate for both RETRO and CEDS. Anthropogenic emissions thus constitute 37–50% of the annual regional VOC source in our base-case inversions and exceed biogenic emissions over the Indo-Gangetic Plain, West India, and South India, and over the entire subcontinent during winter and post-monsoon. Fires are a minor fraction (<7%) of the total regional VOC source in the prior and optimized model. However, evidence suggests that VOC emissions in the fire inventory used here (GFEDv4) are too low over the Indian subcontinent.

Original languageEnglish (US)
Pages (from-to)10525-10545
Number of pages21
JournalJournal of Geophysical Research Atmospheres
Volume124
Issue number19
DOIs
StatePublished - Oct 16 2019

Bibliographical note

Funding Information:
http://www.qa4ecv.eu/ecv/hcho‐p/ https://acdisc.gsfc.nasa.gov/data/Aura_OMI_Level3/OMAERUVd.003/ This work was supported by NASA (NNX14AP89G), NSF (AGS‐1148951), University of Minnesota Doctoral Dissertation Fellowship and by the Minnesota Supercomputing Institute. The authors thank Isabelle De Smedt and the Belgian Institute for Space Aeronomy (BIRA‐IASB) for generating the HCHO retrievals and Christine Wiedinmyer for helpful discussions on biomass burning emission uncertainties. Satellite data used here is publicly available online ( and ). GEOS‐Chem model code is available for download at the GEOS‐Chem website(www.geos‐chem.org).

Funding Information:
This work was supported by NASA (NNX14AP89G), NSF (AGS-1148951), University of Minnesota Doctoral Dissertation Fellowship and by the Minnesota Supercomputing Institute. The authors thank Isabelle De Smedt and the Belgian Institute for Space Aeronomy (BIRA-IASB) for generating the HCHO retrievals and Christine Wiedinmyer for helpful discussions on biomass burning emission uncertainties. Satellite data used here is publicly available online (http://www.qa4ecv.eu/ecv/hcho-p/ and https://acdisc.gsfc.nasa.gov/data/Aura_OMI_Level3/OMAERUVd.003/). GEOS-Chem model code is available for download at the GEOS-Chem website(www.geos-chem.org).

Publisher Copyright:
© 2019. American Geophysical Union. All Rights Reserved.

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