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Estimating Bulk Entrainment With Unaggregated and Aggregated Convection
Author(s) -
Becker Tobias,
Bretherton Christopher S.,
Hohenegger Cathy,
Stevens Bjorn
Publication year - 2018
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 - 10.1002/2017gl076640
Subject(s) - convection , entrainment (biomusicology) , buoyancy , mechanics , turbulence , environmental science , mesoscale meteorology , atmospheric sciences , materials science , meteorology , physics , rhythm , acoustics
To investigate how entrainment is influenced by convective organization, we use the ICON (ICOsahedral Nonhydrostatic) model in a radiative‐convective equilibrium framework, with a 1 km spatial grid mesh covering a 600 by 520 km 2 domain. We analyze two simulations, with unaggregated and aggregated convection, and find that, in the lower free troposphere, the bulk entrainment rate increases when convection aggregates. The increase of entrainment rate with aggregation is caused by a strong increase of turbulence in the close environment of updrafts, masking other effects like the increase of updraft size and of static stability with aggregation. Even though entrainment rate increases with aggregation, updraft buoyancy reduction through entrainment decreases because aggregated updrafts are protected by a moist shell. Parameterizations that wish to represent mesoscale convective organization would need to model this moist shell.