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21st Century Change in Global Small-Size Aerosols from Combustion Emissions
  • +9
  • Meemong Lee,
  • John Worden,
  • Rebecca Bucholz,
  • Helen Worden,
  • Mijeong Park,
  • Yuan Wang,
  • Jiani Yang,
  • Marcin Witek,
  • Hui Su,
  • Brendan Byrne,
  • Kazu Miyazaki,
  • Jonathan Jiang
Meemong Lee
Jet Propulsion Laboratory
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John Worden
Jet Propulsion Laboratory

Corresponding Author:[email protected]

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Rebecca Bucholz
National Center for Atmospheric Research, Boulder, CO
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Helen Worden
National Center for Atmospheric Research, Boulder, CO
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Mijeong Park
National Center for Atmospheric Research, Boulder, CO
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Yuan Wang
California Institute of Technology, Pasadena, CA
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Jiani Yang
California Institute of Technology, Pasadena, CA
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Marcin Witek
Jet propulsion Laboratory, California Institute of Technology, Pasadena, CA
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Hui Su
Jet Propulsion Laboratory
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Brendan Byrne
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
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Kazu Miyazaki
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
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Jonathan Jiang
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
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Abstract

Changes in aerosol optical depth, both positive and negative, are observed across the globe during the 21rst Century. However, attribution of these changes to specific sources is largely uncertain as there are multiple contributing natural and anthropogenic sources that produce aerosols either directly or through secondary chemical reactions. Here we show that satellite-based changes in small-mode AOD between 2002 and 2019 observed in data from MISR can primarily be explained by changes, either directly or indirectly, in combustion emissions. We quantify combustion emissions using MOPITT total column CO observations and the adjoint of the GEOS-Chem global chemistry and transport model. The a priori fire emissions are taken from the Global Fire Emission Data base with small fires (GFED4s) but with fixed a priori for non-fire emissions. Aerosol precursor and direct emissions are updated by re-scaling them with the monthly ratio of the CO posterior to prior emissions. The correlation between modeled and observed AOD improves from a mean of 0.15 to 0.81 for the four industrial regions considered and from 0.52 to 0.75 for the four wildfire-dominant regions considered. Using these updated emissions in the GEOS-Chem global chemistry transport model, our results indicate that surface PM2.5 have declined across many regions of the globe during the 21rst century. For example, PM2.5 over China has declined by ~30% with smaller fractional declines in E. USA and Europe (from fossil emissions) and in S. America (from fires). These results highlight the importance of forest management and cleaner combustion sources in improving air-quality.