Insight into global trends in aerosol composition from 2005 to 2015 inferred from the OMI Ultraviolet Aerosol Index
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 I...
Main Authors: | , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-06-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/18/8097/2018/acp-18-8097-2018.pdf |
Summary: | 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) from 2005 to 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 resolves observed negative UVAI trends well
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. |
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ISSN: | 1680-7316 1680-7324 |