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Turbulence effects on warm‐rain autoconversion in precipitating shallow convection
Author(s) -
Seifert Axel,
Nuijens Louise,
Stevens Bjorn
Publication year - 2010
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.684
Subject(s) - parametrization (atmospheric modeling) , turbulence , environmental science , dissipation , atmospheric sciences , meteorology , convection , turbulence kinetic energy , drizzle , cloud computing , geology , physics , precipitation , radiative transfer , thermodynamics , computer science , operating system , quantum mechanics
A parametrization of the rain formation in warm clouds is developed which includes the effects of turbulence on the collision rate of droplets in a cloud. It is shown that already moderate turbulence with dissipation rates of 400 cm 2 s −3 can lead to a significant speed‐up of the rain formation corresponding to an increase in the autoconversion rate by a factor of 4–6 depending on the size of the droplets. Large‐eddy simulations of trade wind cumuli also produce a significant enhancement of rain formation through turbulence effects on cloud microphysics. In small cumulus clouds, the highest turbulent dissipation rates occur near cloud‐top, which is also the decisive region of the cloud for the initial rain formation. Copyright © 2010 Royal Meteorological Society