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The Role of Small Soluble Aerosols in the Microphysics of Deep Maritime Clouds

Khain, A. P.; Phillips, Vaughan LU ; Benmoshe, N. and Pokrovsky, A. (2012) In Journal of Atmospheric Sciences 69(9). p.2787-2807
Abstract
Some observational evidence-such as bimodal drop size distributions, comparatively high concentrations of supercooled drops at upper levels, high concentrations of small ice crystals in cloud anvils leading to high optical depth, and lightning in the eyewalls of hurricanes-indicates that the traditional view of the microphysics of deep tropical maritime clouds requires, possibly, some revisions. In the present study it is shown that the observed phenomena listed above can be attributed to the presence of small cloud condensation nuclei (CCN) with diameters less than about 0.05 mu m. An increase in vertical velocity above cloud base can lead to an increase in supersaturation and to activation of the smallest CCN, resulting in production of... (More)
Some observational evidence-such as bimodal drop size distributions, comparatively high concentrations of supercooled drops at upper levels, high concentrations of small ice crystals in cloud anvils leading to high optical depth, and lightning in the eyewalls of hurricanes-indicates that the traditional view of the microphysics of deep tropical maritime clouds requires, possibly, some revisions. In the present study it is shown that the observed phenomena listed above can be attributed to the presence of small cloud condensation nuclei (CCN) with diameters less than about 0.05 mu m. An increase in vertical velocity above cloud base can lead to an increase in supersaturation and to activation of the smallest CCN, resulting in production of new droplets several kilometers above the cloud base. A significant increase in supersaturation can be also caused by a decrease in droplet concentration during intense warm rain formation accompanied by an intense vertical velocity. This increase in supersaturation also can trigger in-cloud nucleation and formation of small droplets. Another reason for an increase in supersaturation and in-cloud nucleation can be riming, resulting in a decrease in droplet concentration. It has been shown that successive growth of new nucleated droplets increases supercooled water content and leads to significant ice crystal concentrations aloft. The analysis of the synergetic effect of the smallest CCN and giant CCN on production of supercooled water and ice crystals in cloud anvils allows reconsideration of the role of giant CCN. Significant effects of small aerosols on precipitation and cloud updrafts have been found. The possible role of these small aerosols as well as small aerosols with combination of giant CCN in creating conditions favorable for lightning in deep maritime clouds is discussed. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Atmospheric Sciences
volume
69
issue
9
pages
2787 - 2807
publisher
Amer Meteorological Soc
external identifiers
  • wos:000308280400010
  • scopus:84867934206
ISSN
1520-0469
DOI
10.1175/2011JAS3649.1
language
English
LU publication?
no
id
84779524-86f8-47c5-9ac0-a7d6f233b92f (old id 4587449)
date added to LUP
2014-08-15 10:30:05
date last changed
2017-10-22 03:14:14
@article{84779524-86f8-47c5-9ac0-a7d6f233b92f,
  abstract     = {Some observational evidence-such as bimodal drop size distributions, comparatively high concentrations of supercooled drops at upper levels, high concentrations of small ice crystals in cloud anvils leading to high optical depth, and lightning in the eyewalls of hurricanes-indicates that the traditional view of the microphysics of deep tropical maritime clouds requires, possibly, some revisions. In the present study it is shown that the observed phenomena listed above can be attributed to the presence of small cloud condensation nuclei (CCN) with diameters less than about 0.05 mu m. An increase in vertical velocity above cloud base can lead to an increase in supersaturation and to activation of the smallest CCN, resulting in production of new droplets several kilometers above the cloud base. A significant increase in supersaturation can be also caused by a decrease in droplet concentration during intense warm rain formation accompanied by an intense vertical velocity. This increase in supersaturation also can trigger in-cloud nucleation and formation of small droplets. Another reason for an increase in supersaturation and in-cloud nucleation can be riming, resulting in a decrease in droplet concentration. It has been shown that successive growth of new nucleated droplets increases supercooled water content and leads to significant ice crystal concentrations aloft. The analysis of the synergetic effect of the smallest CCN and giant CCN on production of supercooled water and ice crystals in cloud anvils allows reconsideration of the role of giant CCN. Significant effects of small aerosols on precipitation and cloud updrafts have been found. The possible role of these small aerosols as well as small aerosols with combination of giant CCN in creating conditions favorable for lightning in deep maritime clouds is discussed.},
  author       = {Khain, A. P. and Phillips, Vaughan and Benmoshe, N. and Pokrovsky, A.},
  issn         = {1520-0469},
  language     = {eng},
  number       = {9},
  pages        = {2787--2807},
  publisher    = {Amer Meteorological Soc},
  series       = {Journal of Atmospheric Sciences},
  title        = {The Role of Small Soluble Aerosols in the Microphysics of Deep Maritime Clouds},
  url          = {http://dx.doi.org/10.1175/2011JAS3649.1},
  volume       = {69},
  year         = {2012},
}