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Dependence of entrainment in shallow cumulus convection on vertical velocity and distance to cloud edge
Author(s) -
Tian Yang,
Kuang Zhiming
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl069005
Subject(s) - plume , buoyancy , entrainment (biomusicology) , convection , atmospheric sciences , richardson number , mechanics , stratification (seeds) , meteorology , amplitude , neutral buoyancy , perturbation (astronomy) , geology , vertical velocity , environmental science , physics , optics , seed dormancy , germination , botany , dormancy , rhythm , acoustics , biology , quantum mechanics
The dependence of entrainment rate on environmental conditions and cloud characteristics is investigated using large eddy simulations (LES) of the response of shallow cumulus convection to a small‐amplitude temperature perturbation that is horizontally uniform and localized in height. The simulated cumulus fields are analyzed in the framework of an ensemble of entraining plumes by tracking a large number of Lagrangian parcels embedded in the LES and grouping them into different plumes based on their detrainment heights. The results show that fractional entrainment rate per unit height of a plume is inversely proportional to the plume's vertical velocity and its distance to the cloud edge, while changes in environmental stratification and relative humidity, the plume's buoyancy, or the vertical gradient of its buoyancy due to the temperature perturbation have little effect on the plume's entrainment rate.