Atmospheric convective boundary layer (CBL) entrainment is the downward mixing of free atmospheric air into the CBL as the CBL grows. Primarily, the CBL entrainment is driven by the buoyancy production of turbulence kinetic energy (TKE) due to heating of the lower surface or cooling at the CBL top. The effects of shear-generated turbulence in the CBL are secondary. However, cases of a purely bu...

A convection scheme for climate model is developed based on Tiedtke’s (Mon Weather Rev 117:1779–1800, 1989) bulk mass flux framework and is evaluated with observational data and cloud resolving model simulation data. The main differences between the present parameterization and Tiedtke’s parameterization are the convection trigger, fractional entrainment and detrainment rate formulations, and c...

the baroclinic adjustment is defined as the neutralization of the mean flow by eddies. with the amplitude growth of the baroclinic waves generated by an unstable mean flow, the eddy fluxes increase and act to reduce the meridional temperature gradient or vertical wind shear of the mean flow to subcritical value. this is believed to constitute the basic mechanism of baroclinic adjustment. the co...

Gravity currents are a ubiquitous fluid dynamical phenomenon which involve the horizontal spreading of fluid masses under their own weight or buoyancy. A theoretical model is developed to account for the effects of bulk cooling on the dynamics and morphology of geological gravity currents, with particular focus on mantle plume heads spreading beneath the lithosphere. As many geological gravity ...

This paper formulates a model of mixing in a stratified and turbulent fluid. The model uses the horizontally averaged vertical buoyancy gradient and the density of turbulent kinetic energy as variables. Heuristic ‘mixing-length’ arguments lead to a coupled set of parabolic differential equations. A particular form of mechanical forcing is proposed; for certain parameter values the relationship ...

Coarse resolution numerical ocean models must typically include a parameterisation for mesoscale turbulence. A common recipe for such parameterisations is to invoke mixing of some tracer quantity, such as potential vorticity or buoyancy. However, it is well known that eddy fluxes include large rotational components which necessarily do not lead to any mixing; eddy diffusivities diagnosed from u...

A steady source of buoyancy creates a plume. Experi­ mental and theoretical studies of plumes have been mainly concerned with the far-field (self-similar) velocity and den­ sity profiles. •-3 Yet in many practical situations, knowledge regarding the rate of molecular scale mixing of the buoyant fluid with its environment is needed. This is especially true in the context of atmospheric studies, ...

Direct numerical simulations of stably stratified homogeneous turbulence, with and without mean shear, are used to investigate the three-dimensional structure, evolution and energetic significance of density overturns. Although the flow conditions are idealized, examination of the full-field simulation data provides insight into flow energetics and mixing which may assist in the interpretation ...

Using a linear stability analysis and two and three-dimensional nonlinear simulations, we study the physics of buoyancy instabilities in a combined thermal and relativistic (cosmic ray) plasma, motivated by the application to clusters of galaxies. We argue that cosmic ray diffusion is likely to be slow compared to the buoyancy time on large length scales, so that cosmic rays are effectively adi...