Drop size-dependent chemical composition of clouds and fogs. Part II: Relevance to interpreting the aerosol/trace gas/fog system

Size-resolved fog drop chemical composition measurements were obtained during a radiation fog campaign near Davis, California in December 1998/January 1999 (reported in Reilly et al., Atmos. Environ. 35(33) (2001) 5717; Moore et al., Atmos. Environ. this issue). Here we explore how knowledge of this...

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Bibliographic Details
Published in:Atmospheric environment (1994) 2004-03, Vol.38 (10), p.1403-1415
Main Authors: Moore, Katharine F., Eli Sherman, D., Reilly, Jill E., Hannigan, Michael P., Lee, Taehyoung, Collett, Jeffrey L.
Format: Article
Language:English
Subjects:
Deposition velocity
Earth, ocean, space
Exact sciences and technology
External geophysics
Fog chemistry
Meteorology
Nitrous acid
Occult deposition
Phase equilibrium
Radiation fog
Sacramento Valley
Water in the atmosphere (humidity, clouds, evaporation, precipitation)
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Summary:Size-resolved fog drop chemical composition measurements were obtained during a radiation fog campaign near Davis, California in December 1998/January 1999 (reported in Reilly et al., Atmos. Environ. 35(33) (2001) 5717; Moore et al., Atmos. Environ. this issue). Here we explore how knowledge of this size-dependent drop composition—particularly from the newly developed Colorado State University 5-Stage cloud water collector—helps to explain additional observations in the fog environment. Size-resolved aerosol measurements before and after fog events indicate relative depletion of large (>2 μm in diameter) particles during fog accompanied by a relative increase in smaller aerosol particle concentrations. Fog equivalent air concentrations suggest that entrainment of additional particles and in-fog sedimentation contributed to observed changes in the aerosol size distribution. Calculated deposition velocities indicate that sedimentation was an important atmospheric removal mechanism for some species. For example, nitrite typically has a larger net deposition velocity than water and its mass is found preferentially in the largest drops most likely to sediment rapidly. Gas–liquid equilibria in fog for NO 3 −/HNO 3, NH 4 +/NH 3, and NO 2 −/HONO were examined. While these systems appear to be close to equilibrium or relative equilibrium during many time periods, divergences are observed, particularly for low liquid water content (
ISSN:1352-2310
1873-2844
DOI:10.1016/j.atmosenv.2003.12.014