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| Titel |
Studying an effect of salt powder seeding used for precipitation enhancement from convective clouds |
| VerfasserIn |
A. S. Drofa, V. N. Ivanov, D. Rosenfeld, A. G. Shilin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 16 ; Nr. 10, no. 16 (2010-08-27), S.8011-8023 |
| Datensatznummer |
250008734
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| Publikation (Nr.) |
 copernicus.org/acp-10-8011-2010.pdf |
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| Zusammenfassung |
Experimental and theoretical studies of cloud microstructure modification
with hygroscopic particles for obtaining additional precipitation amounts
from convective clouds are performed. The experiment used salt powder with
the particle sizes that gave the greatest effectiveness according to the
simulations of Segal et al. (2004). The experiments were carried out in a
cloud chamber at the conditions corresponding to the formation of convective
clouds. The results have shown that the introduction of the salt powder
before a cloud medium is formed in the chamber results in the formation on a
"tail" of additional large drops. In this case seeding with the salt
powder leads also to enlargement of the whole population of cloud drops and
to a decrease of their total concentration as compared to a cloud medium
that is formed on background aerosols. These results are the positive
factors for stimulating coagulation processes in clouds and for subsequent
formation of precipitation in them. An overseeding effect, which is
characterized by increased droplet concentration and decreased droplet size,
was not observed even at high salt powder concentrations.
The results of numerical simulations have shown that the transformation of
cloud drop spectra induced by the introduction of the salt powder results in
more intense coagulation processes in clouds as compared to the case of
cloud modification with hygroscopic particles with relatively narrow
particle size distributions, and for the distribution of the South African
hygroscopic flares. The calculation results obtained with a one-dimensional
model of a warm convective cloud demonstrated that the effect of salt powder
on clouds (total amounts of additional precipitation) is significantly
higher than the effect caused by the use of hygroscopic particles with
narrow particle size distributions at comparable consumptions of seeding
agents, or with respect to the hygroscopic flares. Here we show that seeding
at rather low consumption rate of the salt powder initiates precipitation
from otherwise non precipitating warm convective clouds, mainly by the
effect of adding large cloud drops to the tail of the distribution. |
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