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| Titel |
Impact of black carbon aerosol over Italian basin valleys: high-resolution measurements along vertical profiles, radiative forcing and heating rate |
| VerfasserIn |
L. Ferrero, M. Castelli, B. S. Ferrini, M. Moscatelli, M. G. Perrone, G. Sangiorgi, L. D'Angelo, G. Rovelli, B. Moroni, F. Scardazza, G. Mocnik, E. Bolzacchini, M. Petitta, D. Cappelletti |
| 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 ; 14, no. 18 ; Nr. 14, no. 18 (2014-09-16), S.9641-9664 |
| Datensatznummer |
250119033
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| Publikation (Nr.) |
 copernicus.org/acp-14-9641-2014.pdf |
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| Zusammenfassung |
A systematic study of black carbon (BC) vertical profiles measured at
high-resolution over three Italian basin valleys (Terni Valley, Po Valley and
Passiria Valley) is presented. BC vertical profiles are scarcely available in
literature. The campaign lasted 45 days and resulted in 120 measured vertical
profiles. Besides the BC mass concentration, measurements along the vertical
profiles also included aerosol size distributions in the optical particle
counter range, chemical analysis of filter samples and a full set of
meteorological parameters. Using the collected experimental data, we
performed calculations of aerosol optical properties along the vertical
profiles. The results, validated with AERONET data, were used as inputs to a
radiative transfer model (libRadtran). The latter allowed an estimation of
vertical profiles of the aerosol direct radiative effect, the atmospheric
absorption and the heating rate in the lower troposphere.
The present measurements revealed some common behaviors over the studied
basin valleys. Specifically, at the mixing height, marked concentration drops
of both BC (range: from −48.4 ± 5.3 to −69.1 ± 5.5%) and
aerosols (range: from −23.9 ± 4.3 to −46.5 ± 7.3%) were
found. The measured percentage decrease of BC was higher
than that of aerosols: therefore, the BC aerosol fraction decreased upwards.
Correspondingly, both the absorption and scattering coefficients decreased
strongly across the mixing layer (range: from −47.6 ± 2.5 to
−71.3 ± 3.0% and from −23.5 ± 0.8 to
−61.2 ± 3.1%, respectively) resulting in a single-scattering
albedo increase along height (range: from +4.9 ± 2.2 to
+7.4 ± 1.0%).
This behavior influenced the vertical distribution of the aerosol direct
radiative effect and of the heating rate. In this respect, the highest
atmospheric absorption of radiation was predicted below the mixing height
(~ 2–3 times larger than above it) resulting in a heating rate characterized
by a vertical negative gradient (range: from −2.6 ± 0.2 to
−8.3 ± 1.2 K day−1 km−1). In conclusion, the present results suggest
that the BC below the mixing height has the potential to promote a negative feedback on the atmospheric stability over basin valleys,
weakening the ground-based thermal inversions and increasing the dispersal
conditions. |
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