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A numerical model of cumulonimbus convection generating a protected core
Author(s) -
Berson F. A.,
Baird G.
Publication year - 1975
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.49710143014
Subject(s) - buoyancy , hydrostatic equilibrium , mechanics , turbulence , convection , lapse rate , meteorology , geology , environmental science , physics , quantum mechanics
The theory of buoyant motion in a turbulent environment due to Priestley (1953) is applied to steady‐state Cb updraught. An axisymmetric numerical model of columnar convection is modified to allow for radial cloud structure and internal turbulence. In this model the net vertical body force on a fluid element is the buoyancy relative to adjacent elements, and represents a residual of environment‐referred buoyancy and non‐hydrostatic pressure gradient. Moisture exchange and lateral transfer of momentum and heat by mass exchange with the environment on the scale of the cloud are disregarded, yet the model gives realistic updraught velocities and cloud depth. It simulates such features as a dome rising from a protected core of the cloud, oscillating motion of cloud tops and penetration of the tropopause. In some respects the predicted behaviour compares favourably with actual measurements. An incidental result concerns the generating gross buoyancy which is determined by the ambient and pseudo‐adiabatic temperature lapse rates. It appears that the values of the latter rate published in Smithonian Meteorological Tables and incorporated in pseudo‐adiabats on aerological diagrams, are in error.