Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign
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Authors
Hammer, Emanuel
Roberts, Greg
Elias, Thierry
Hofer, Julian
Hoyle, Christopher R.
Bukowiecki, Nicolas
Dupont, Jean-Charles
Burnet, Frederic
Baltensperger, Urs
Author (Corporation)
Publication date
2014
Typ of student thesis
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Type
01A - Journal article
Editors
Editor (Corporation)
Supervisor
Parent work
Atmospheric Chemistry and Physics
Special issue
DOI of the original publication
Link
Series
Series number
Volume
14
Issue / Number
19
Pages / Duration
10517–10533
Patent number
Publisher / Publishing institution
Copernicus
Place of publication / Event location
Göttingen
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Abstract
Fog-induced visibility reduction is responsible for a variety of hazards in the transport sector. Therefore there is a large demand for an improved understanding of fog formation and thus improved forecasts. Improved fog forecasts require a better understanding of the numerous complex mechanisms during the fog life cycle. During winter 2012/13 a field campaign called ParisFog aiming at fog research took place at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research). SIRTA is located about 20 km southwest of the Paris city center, France, in a semi-urban environment. In situ activation properties of the prevailing fog were investigated by measuring (1) total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems; (2) interstitial hydrated aerosol and fog droplet size distributions at ambient conditions; and (3) cloud condensation nuclei (CCN) number concentration at different supersaturations (SS) with a CCN counter. The aerosol particles were characterized regarding their hygroscopic properties, fog droplet activation behavior and contribution to light scattering for 17 developed fog events. Low particle hygroscopicity with an overall median of the hygroscopicity parameter, κ, of 0.14 was found, likely caused by substantial influence from local traffic and wood burning emissions. Measurements of the aerosol size distribution at ambient RH revealed that the critical wet diameter, above which the hydrated aerosols activate to fog droplets, is rather large (with a median value of 2.6μm) and is highly variable (ranging from 1 to 5μm) between the different fog events. Thus, the number of activated fog droplets was very small and the non-activated hydrated particles were found to contribute significantly to the observed light scattering and thus to the reduction in visibility. Combining all experimental data, the effective peak supersaturation, SSpeak, a measure of the peak supersaturation during the fog formation, was determined. The median SSpeak value was estimated to be in the range from 0.031 to 0.046% (upper and lower limit estimations), which is in good agreement with previous experimental and modeling studies of fog.
Keywords
Subject (DDC)
550 - Geowissenschaften
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ISBN
ISSN
1680-7324
1680-7316
1680-7316
Language
English
Created during FHNW affiliation
No
Strategic action fields FHNW
Publication status
Published
Review
Peer review of the complete publication
Open access category
Gold
License
Citation
HAMMER, Emanuel, Martin GYSEL, Greg ROBERTS, Thierry ELIAS, Julian HOFER, Christopher R. HOYLE, Nicolas BUKOWIECKI, Jean-Charles DUPONT, Frederic BURNET, Urs BALTENSPERGER und Ernest WEINGARTNER, 2014. Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign. Atmospheric Chemistry and Physics. 2014. Bd. 14, Nr. 19, S. 10517–10533. DOI 10.5194/acp-14-10517-2014. Verfügbar unter: https://doi.org/10.26041/fhnw-8130