Fog chemical composition and its feedback to fog water fluxes, water vapor fluxes, and microphysical evolution of two events near Paris

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Title:	Fog chemical composition and its feedback to fog water fluxes, water vapor fluxes, and microphysical evolution of two events near Paris
Authors:	柯奧圖;Degefie, D.T.;El-Madany, T.-S.;Held, M.;Hejkal, J.;Hammer, E.;Dupont, J.-C.;Haeffelin, M.;Fleischer, E.;Klemm, O.
Contributors:	地球科學學院大氣科學學系
Keywords:	air;ammonium compounds;calcium;Chemical composition;droplets;fog (meteorology);France;ions;nitrates;polytetrafluoroethylene;Radiation fog;Sciences of the Universe;Stratus lowering fog;sulfates;Turbulent fluxes;water vapor
Date:	2015-10-01
Issue Date:	2026-04-21 14:08:00 (UTC+8)
Publisher:	Elsevier BV;Elsevier B.V
Abstract:	摘要： The chemical composition of collected fog water and its temporal evolution was studied during the PARISFOG campaign in winter 2012/2013 at the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphéric) atmospheric observatory outside Paris, France. A further development of the caltech active fog collector was applied, in which the collected fog water gets into contact with Teflon and polyether ether ketone (PEEK) material exclusively. The collector was operational whenever the visibility was below 1000m. In addition, the turbulent and gravitational fluxes of fog water and water vapor flux were used to examine in detail the temporal evolution the chemical composition of two fogs. The technique was applied to two fog events, one representing a radiation fog and the other one representing a stratus lowering fog. The result revealed that the dominant inorganic species in the fog water were NH4+, NO3−, Ca2+ and SO42−, which accounted for more than 85% of the ion balance. The pH ranged from 3.7 to 6.2. In the evolution the two fog events, the interaction among the turbulent fog water flux, gravitational fog water flux and water vapor flux controlled the major ion loads (amount of ions, dissolved in fog droplets per volume of air) and ion concentrations (amount dissolved per volume of liquid water) of the fog water. In the radiation fog event, an increase of ion loads and ion concentrations occurred when the direction of water vapor flux towards to the place where the condensation process occurred. A decrease of ion loads and ion concentrations mainly happened by gravitational fog water flux with a minor contribution from turbulent fog water flux. However, when the turbulent water vapor flux was oriented downward, it turned the turbulent fog water flux upward and offset the removal of ions in the fog. In the stratus lowering fog event, the turbulent fog water flux and the gravitational water flux together mainly contributed to the fog water deposition and removal of ions. Increases of ion loads and ion concentrations occurred in response to slight downward water vapor flux. This study also indicates that the turbulent transport of fog droplets contributed to the preferential deposition of certain sizes fog droplets such that it affected the chemical composition of the fog water. For instance, both the NO3− concentration and load decreased fast as compared to NH4+ and SO42− during the deposition period. This suggested that the chemical composition was dependent on fog droplets size. •Fog chemical composition is influenced by turbulence processes.•Upward turbulent fog water flux maintains ion loads in radiation fog.•Downward turbulent fog water flux removes ions from fog together with gravitational flux.•Fog droplets turbulent flux influence ion concentrations differently for different ions.•Fog chemical composition dependent on fog droplets size. 出版者： Elsevier B.V 出版日期： 2015-10-01 出處： Atmospheric research, 2015-10, Vol.164-165, p.328-338 資源來源： Elsevier ScienceDirect Journals Complete 版權： 2015 Elsevier B.V. 版權： licence_http://creativecommons.org/publicdomain/zero 識別號： ISSN: 0169-8095 識別號： EISSN: 1873-2895 識別號： DOI: 10.1016/j.atmosres.2015.05.002
Appears in Collections:	[Department of Atmospheric Sciences] journal & Dissertation

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