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dc.contributor.advisorJacob, Daniel J.
dc.contributor.authorZhu, Lei
dc.date.accessioned2018-12-20T08:11:07Z
dc.date.created2017-03
dc.date.issued2017-01-06
dc.date.submitted2017
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:37944975*
dc.description.abstractFormaldehyde (HCHO) column data from satellites are widely used as a proxy for emissions of volatile organic compounds (VOCs), but validation of the data has been extremely limited. Here I use highly accurate HCHO aircraft observations from the NASA SEAC4RS campaign over the Southeast US in 2013 summer to validate and intercompare currently available HCHO retrievals. All retrievals feature a HCHO maximum over Arkansas and Louisiana, consistent with the aircraft observations and GEOS-Chem model results, and reflecting high emissions of biogenic isoprene. The retrievals are also broadly consistent in their spatial (r = 0.4–0.8 on a 0.5° × 0.5° grid) and daily variability (r = 0.5–0.8) over the Southeast US in 2013 summer. Validation results show that HCHO column data provide a reliable proxy for isoprene emission variability but with a low mean bias (20–51%) due both to the spectral fitting and the scattering weights. I apply the corrected OMI data in the following studies. First, I show that temporal oversampling of OMI HCHO column data for 2005–2008 enables detection of urban and industrial plumes in eastern Texas including Houston, Port Arthur, and Dallas/Fort Worth. By spatially integrating the HCHO enhancement in the Houston plume observed by OMI, I estimate an anthropogenic HCHO source of 250 ± 140 kmol h-1, implying that anthropogenic highly reactive VOC emissions in Houston are 4.8 ± 2.7 times higher than reported by the US Environmental Protection Agency inventory (EPA). I then examine the interannual variability of temperature-independent HCHO columns over North America from 2005 to 2014. Significant trends are found to be likely driven by tightening emission controls over the Houston-Galveston-Brazoria area (-2.2% 0.7% a-1), by oil/gas extraction activities over the Floyd shale in Alabama (-1.8% 0.7% a-1) and the Athabasca oil sands in Alberta (4.7% 1.1% a-1), and by reforestation over the northwestern US (4.7% 1.0% a-1). Variation in HCHO columns may also be associated with changing crop cover in the midwest US and with changing wildfire activity in California. Finally, I use 2005–2015 OMI HCHO column data to map surface air HCHO concentrations across the contiguous US. Results are in good agreement with high-quality observations from urban sites and a factor of 2 lower than data from the EPA network. I estimate that up to 6600–13200 people in the US will develop cancer over their lifetimes by exposure to outdoor HCHO. I also find out that NOx emission controls to improve ozone air quality have a co-benefit in reducing HCHO-related cancer risks.
dc.description.sponsorshipEngineering and Applied Sciences - Engineering Sciences
dc.format.mimetypeapplication/pdf
dc.language.isoen
dash.licenseLAA
dc.subjectAtmospheric Sciences
dc.subjectEnvironmental Sciences
dc.titleObserving atmospheric formaldehyde from space: validation and implications
dc.typeThesis or Dissertation
dash.depositing.authorZhu, Lei
dc.date.available2018-12-20T08:11:07Z
thesis.degree.date2017
thesis.degree.grantorGraduate School of Arts & Sciences
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy
dc.contributor.committeeMemberMickley, Loretta J.
dc.contributor.committeeMemberChance, Kelly V.
dc.contributor.committeeMemberWofsy, Steven C.
dc.type.materialtext
thesis.degree.departmentEngineering and Applied Sciences - Engineering Sciences
dash.identifier.vireohttp://etds.lib.harvard.edu/gsas/admin/view/1329
dc.description.keywordsFormaldehyde; Satellite; VOCs; Trend; Validation
dash.author.emailforleizhu@gmail.com


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