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| Titel |
Vertically-resolved particle size distribution within and above the mixing layer over the Milan metropolitan area |
| VerfasserIn |
L. Ferrero, M. G. Perrone, S. Petraccone, G. Sangiorgi, B. S. Ferrini, C. Porto, Z. Lazzati, D. Cocchi, F. Bruno, F. Greco, A. Riccio, E. Bolzacchini |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 8 ; Nr. 10, no. 8 (2010-04-27), S.3915-3932 |
| Datensatznummer |
250008381
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| Publikation (Nr.) |
 copernicus.org/acp-10-3915-2010.pdf |
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| Zusammenfassung |
Vertical aerosol profiles were directly measured over the city of Milan
during three years (2005–2008) of field campaigns. An optical particle
counter, a portable meteorological station and a miniaturized cascade
impactor were deployed on a tethered balloon. More than 300 vertical
profiles were measured, both in winter and summer, mainly in conditions of
clear, dry skies.
The mixing height was determined from the observed vertical aerosol
concentration gradient, and from potential temperature and relative humidity
profiles. Results show that inter-consistent mixing heights can be retrieved
highlighting good correlations between particle dispersion in the atmosphere
and meteorological parameters. Mixing height growth speed was calculated for
both winter and summer showing the low potential atmospheric dispersion in
winter.
Aerosol number size distribution and chemical composition profiles allowed
us to investigate particle behaviour along height. Aerosol measurements
showed changes in size distribution according to mixing height. Coarse
particle profiles (dp>1.6 μm) were distributed differently than
the fine ones (dp<1.6 μm) were, at different heights of the
mixing layer. The sedimentation process influenced the coarse particle
profiles, and led to a reduction in mean particle diameter for those
particles observed by comparing data above the mixing height with ground
data (−14.9±0.6% in winter and −10.7±1.0% in summer).
Conversely, the mean particle diameter of fine particles increased above the
mixing height under stable atmospheric conditions; the average increase,
observed by comparing data above the mixing height with ground data, was
+2.1±0.1% in winter and +3.9±0.3% in summer. A
hierarchical statistical model was created to describe the changes in the
size distribution of fine particles along height. The proposed model can be
used to estimate the typical vertical profile characterising launches within
pre-specified groups starting from: aerosol size and meteorological
conditions measured at ground-level, and a mixing height estimation. The
average increase of fine particle diameter, estimated on the basis of the
model, was +1.9±0.5% in winter and +6.1±1.2% in summer,
in keeping with experimental findings. |
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