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| Titel |
The effects of turbulent collision–coalescence on precipitation formation and precipitation-dynamical feedbacks in simulations of stratocumulus and shallow cumulus convection |
| VerfasserIn |
C. N. Franklin |
| 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 ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-01), S.6557-6570 |
| Datensatznummer |
250118850
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| Publikation (Nr.) |
 copernicus.org/acp-14-6557-2014.pdf |
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| Zusammenfassung |
| A double moment warm rain scheme that includes the effects of turbulence on
droplet collision rates has been implemented in a large-eddy model to
investigate the impact of turbulence effects on clouds and precipitation.
Simulations of shallow cumulus and stratocumulus show that different
precipitation-dynamical feedbacks occur in these regimes when the effects of
turbulence are included in the microphysical processes. In both cases
inclusion of turbulent microphysics increases precipitation due to a more
rapid conversion of cloud water to rain. In the shallow convection case, the
greater water loading in the upper cloud levels reduces the buoyancy
production of turbulent kinetic energy and the entrainment. The
stratocumulus case on the other hand shows a weak positive precipitation
feedback, with enhanced rainwater producing greater evaporation, stronger
circulations and more turbulence. Sensitivity studies in which the cloud
droplet number was varied show that greater number concentrations suppress
the stratocumulus precipitation leading to larger liquid water paths. This
positive second indirect aerosol effect shows no sensitivity to whether or
not the effects of turbulence on droplet collision rates are included. While
the sign of the second indirect effect is negative in the shallow convection
case whether the effects of turbulence are considered or not, the magnitude
of the effect is doubled when the turbulent microphysics are used. It is
found that for these two different cloud regimes turbulence has a larger
effect than cloud droplet number and the use of a different bulk
microphysics scheme on producing rainfall in shallow cumuli. However, for
the stratocumulus case examined here, the effects of turbulence on rainfall
are not statistically significant and instead it is the cloud droplet number
concentration or the choice of bulk microphysics scheme that has the largest
control on the rain water. |
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