Hydrophobic particles can activate at lower relative humidity than slightly hygroscopic ones: a Kohler theory incorporating surface fixed charge

Anthony S. Wexler, Zhaozhu Ge

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

A number of laboratory experiments indicate that hydrophobic carbonaceous particles activate at lower supersaturations than is predicted by Kohler theory. Since a significant fraction of the global energy balance uncertainty is due to the so-called indirect effect, that of clouds, quantifying which particles activate is crucial to accurate prediction of climate. Most material surfaces obtain a fixed charge in water, and this is the case for many materials found in atmospheric aerosols. This fixed charge generates a charge double layer near the material surface which lowers the water activity. In the presence of this surface fixed charge, hydrophobic particles activate at low supersaturations. Since a small number of soluble ions in the particles causes them to only activate at higher supersaturations, surface charge activation is not relevant to activation of particles in the atmosphere. Thus laboratory experiments that measure the growth and activation of hydrophobic particles are measuring an effect, the surface charge effect, that is probably not relevant to the atmosphere.

Original languageEnglish (US)
Pages (from-to)6083-6088
Number of pages6
JournalJournal of Geophysical Research: Atmospheres
Volume103
Issue numberD6
StatePublished - Mar 27 1998
Externally publishedYes

Fingerprint

Supersaturation
humidity
relative humidity
Atmospheric humidity
Chemical activation
Surface charge
supersaturation
Atmospheric aerosols
Water
activation
Energy balance
Experiments
Ions
atmospheres
atmosphere
aerosols
water activity
energy balance
water
climate

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

Cite this

Hydrophobic particles can activate at lower relative humidity than slightly hygroscopic ones : a Kohler theory incorporating surface fixed charge. / Wexler, Anthony S.; Ge, Zhaozhu.

In: Journal of Geophysical Research: Atmospheres, Vol. 103, No. D6, 27.03.1998, p. 6083-6088.

Research output: Contribution to journalArticle

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