Please use this identifier to cite or link to this item: https://oar.tib.eu/jspui/handle/123456789/5667
Files in This Item:
File SizeFormat 
Hammer2014.pdf5,61 MBAdobe PDFView/Open
Title: Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign
Authors: Hammer, E.Gysel, M.Roberts, G.C.Elias, T.Hofer, J.Hoyle, C.R.Bukowiecki, N.Dupont, J.-C.Burnet, F.Baltensperger, U.Weingartner, E.
Publishers Version: https://doi.org/10.5194/acp-14-10517-2014
Issue Date: 2014
Published in: Atmospheric Chemistry and Physics Vol. 14 (2014), No. 19
Publisher: Göttingen : Copernicus
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: aerosol; cloud condensation nucleus; cloud droplet; fog; forecasting method; hygroscopicity; particle size; size distribution; winter; France; Ile de France; Paris; Ville de Paris
DDC: 550
License: CC BY 3.0 Unported
Link to License: https://creativecommons.org/licenses/by/3.0/
Appears in Collections:Umweltwissenschaften



This item is licensed under a Creative Commons License Creative Commons