Observations and regional modeling of aerosol optical properties, speciation and size distribution over Northern Africa and western Europe
The aerosol speciation and size distribution is modeled during the summer 2013 and over a large area encompassing Africa, Mediterranean and western Europe. The modeled aerosol is compared to available measurements such as the AERONET aerosol optical depth (AOD) and aerosol size distribution (ASD)...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/12961/2016/acp-16-12961-2016.pdf |
| Summary: | The aerosol speciation and size distribution is modeled during the summer
2013 and over a large area encompassing Africa, Mediterranean and western
Europe. The modeled aerosol is compared to available measurements such as the
AERONET aerosol optical depth (AOD) and aerosol size distribution (ASD) and
the EMEP network for surface concentrations of particulate matter PM<sub>2.5</sub>,
PM<sub>10</sub> and inorganic species (nitrate, sulfate and ammonium). The main
goal of this study is to quantify the model ability to realistically model
the speciation and size distribution of the aerosol. Results first showed
that the long-range transport pathways are well reproduced and mainly
constituted by mineral dust: spatial correlation is ≈ 0.9 for AOD
and Ångström exponent, when temporal correlations show that the day-to-day
variability is more difficult to reproduce. Over Europe, PM<sub>2.5</sub> and
PM<sub>10</sub> have a mean temporal correlation of ≈ 0.4 but the lowest
spatial correlation ( ≈ 0.25 and 0.62, respectively), showing that
the fine particles are not well localized or transported. Being short-lived
species, the uncertainties on meteorology and emissions induce these
lowest scores. However, time series of PM<sub>2.5</sub> with the speciation show a
good agreement between model and measurements and are useful for
discriminating
the aerosol composition. Using a classification from the south (Africa) to
the north (northern Europe), it is shown that mineral dust relative mass
contribution decreases from 50 to 10 % when nitrate increases from 0
to 20 % and all other species, sulfate, sea salt, ammonium, elemental carbon,
primary organic matter, are constant. The secondary organic aerosol
contribution is between 10 and 20 % with a maximum at the latitude of the
Mediterranean Sea (Spanish stations). For inorganic species, it is shown that
nitrate, sulfate and ammonium have a mean temporal correlation of 0.25, 0.37
and 0.17, respectively. The spatial correlation is better (0.25, 0.5 and
0.87), showing that the mean values may be biased but the spatial localization
of sulfate and ammonium is well reproduced. The size distribution is compared
to the AERONET product and it is shown that the model fairly reproduces the
main values for the fine and coarse mode. In particular, for the fine mode,
the model overestimates the aerosol mass in Africa and underestimates it in
Europe. |
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| ISSN: | 1680-7316 1680-7324 |