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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1183
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Insight into Global Trends in Aerosol Composition over 2005–2015 Inferred from the OMI Ultraviolet Aerosol Index
Melanie S. Hammer1, Randall V. Martin1,2, Chi Li1, Omar Torres3, Max Manning1, and Brian L. Boys1 1Department of Physics and Atmospheric Science, Dalhousie University, Canada
2Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
3Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, 20770, USA
Abstract. Observations of aerosol scattering and absorption offer valuable information about aerosol composition. We apply a simulation of the Ultraviolet Aerosol Index (UVAI), a method of detecting aerosol absorption from satellite observations, to interpret UVAI values observed by the Ozone Monitoring Instrument (OMI) over 2005–2015 to understand global trends in aerosol composition. We conduct our simulation using the vector radiative transfer model VLIDORT with aerosol fields from the global chemical transport model GEOS-Chem. We examine the 2005–2015 trends in individual aerosol species from GEOS-Chem, and apply these trends to the UVAI simulation to calculate the change in simulated UVAI due to the trends in individual aerosol species. We find that global trends in the UVAI are largely explained by trends in absorption by mineral dust, absorption by brown carbon, and scattering by secondary inorganic aerosol. Trends in absorption by mineral dust dominate the simulated UVAI trends over North Africa, the Middle-East, East Asia, and Australia. The UVAI simulation well resolves observed negative UVAI trends over Australia, but underestimates positive UVAI trends over North Africa and Central Asia near the Aral Sea, and underestimates negative UVAI trends over East Asia. We find evidence of an increasing dust source from the desiccating Aral Sea, that may not be well represented by the current generation of models. Trends in absorption by brown carbon dominate the simulated UVAI trends over biomass burning regions. The UVAI simulation reproduces observed negative trends over central South America and West Africa, but underestimates observed UVAI trends over boreal forests. Trends in scattering by secondary inorganic aerosol dominate the simulated UVAI trends over the eastern United States and eastern India. The UVAI simulation slightly overestimates the observed positive UVAI trends over the eastern United States, and underestimates the observed negative UVAI trends over India. Quantitative simulation of the OMI UVAI offers new insight into global trends in aerosol composition.
Citation: Hammer, M. S., Martin, R. V., Li, C., Torres, O., Manning, M., and Boys, B. L.: Insight into Global Trends in Aerosol Composition over 2005–2015 Inferred from the OMI Ultraviolet Aerosol Index, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1183, in review, 2018.
Melanie S. Hammer et al.
Melanie S. Hammer et al.
Melanie S. Hammer et al.

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We apply a simulation of the Ultraviolet Aerosol Index (UVAI), a method of detecting aerosol absorption from satellite observations, to interpret UVAI values observed by the Ozone Monitoring Instrument (OMI) over 2005–2015 to understand global trends in aerosol composition. We find that global trends in the UVAI are largely explained by trends in absorption by mineral dust, absorption by brown carbon, and scattering by secondary inorganic aerosol.
We apply a simulation of the Ultraviolet Aerosol Index (UVAI), a method of detecting aerosol...
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