Studying the vertical aerosol extinction coefficient by comparing in situ airborne data and elastic backscatter lidar
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Authors
Rosati, Bernadette
Herrmann, Erik
Bucci, Silvia
Fierli, Federico
Cairo, Francesco
Tillmann, Ralf
Größ, Johannes
Gobbi, Gian Paolo
Di Liberto, Luca
Author (Corporation)
Publication date
2016
Typ of student thesis
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Collections
Type
01A - Journal article
Editors
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Parent work
Atmospheric Chemistry and Physics
Special issue
DOI of the original publication
Link
Series
Series number
Volume
16
Issue / Number
7
Pages / Duration
4539–4554
Patent number
Publisher / Publishing institution
Copernicus
Place of publication / Event location
Göttingen
Edition
Version
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Abstract
Vertical profiles of aerosol particle optical properties were explored in a case study near the San Pietro Capofiume (SPC) ground station during the PEGASOS Po Valley campaign in the summer of 2012. A Zeppelin NT airship was employed to investigate the effect of the dynamics of the planetary boundary layer at altitudes between ∼ 50 and 800 m above ground. Determined properties included the aerosol particle size distribution, the hygroscopic growth factor, the effective index of refraction and the light absorption coefficient. The first three parameters were used to retrieve the light scattering coefficient. Simultaneously, direct measurements of both the scattering and absorption coefficient were carried out at the SPC ground station. Additionally, a single wavelength polarization diversity elastic lidar system provided estimates of aerosol extinction coefficients using the Klett method to accomplish the inversion of the signal, for a vertically resolved comparison between in situ and remote-sensing results. Note, however, that the comparison was for the most part done in the altitude range where the overlap function is incomplete and accordingly uncertainties are larger. First, the airborne results at low altitudes were validated with the ground measurements. Agreement within approximately ±25 and ±20 % was found for the dry scattering and absorption coefficient, respectively. The single scattering albedo, ranged between 0.83 and 0.95, indicating the importance of the absorbing particles in the Po Valley region. A clear layering of the atmosphere was observed during the beginning of the flight (until ∼ 10:00 LT – local time) before the mixing layer (ML) was fully developed. Highest extinction coefficients were found at low altitudes, in the new ML, while values in the residual layer, which could be probed at the beginning of the flight at elevated altitudes, were lower. At the end of the flight (after ∼ 12:00 LT) the ML was fully developed, resulting in constant extinction coefficients at all altitudes measured on the Zeppelin NT. Lidar estimates captured these dynamic features well and good agreement was found for the extinction coefficients compared to the in situ results, using fixed lidar ratios (LR) between 30 and 70 sr for the altitudes probed with the Zeppelin. These LR are consistent with values for continental aerosol particles that can be expected in this region.
Keywords
Subject (DDC)
620 - Ingenieurwissenschaften und Maschinenbau
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ISBN
ISSN
1680-7324
1680-7316
1680-7316
Language
English
Created during FHNW affiliation
Yes
Strategic action fields FHNW
Publication status
Published
Review
Peer review of the complete publication
Open access category
Gold
License
Citation
ROSATI, Bernadette, Erik HERRMANN, Silvia BUCCI, Federico FIERLI, Francesco CAIRO, Martin GYSEL, Ralf TILLMANN, Johannes GRÖSS, Gian Paolo GOBBI, Luca DI LIBERTO, Guido DI DONFRANCESCO, Alfred WIEDENSOHLER, Ernest WEINGARTNER, Annele VIRTANEN, Thomas F. MENTEL und Urs BALTENSPERGER, 2016. Studying the vertical aerosol extinction coefficient by comparing in situ airborne data and elastic backscatter lidar. Atmospheric Chemistry and Physics. 2016. Bd. 16, Nr. 7, S. 4539–4554. DOI 10.5194/acp-16-4539-2016. Verfügbar unter: https://doi.org/10.26041/fhnw-8060