IX.—On some Causes of the Formation of Anticyclonic Stratus as observed from Aeroplanes

1918 ◽  
Vol 37 ◽  
pp. 137-148 ◽  
Author(s):  
C. K. M. Douglas
Keyword(s):  
Temperature Gradient ◽  
Adiabatic Temperature ◽  
Large Area ◽  
Stratus Clouds ◽  
Adiabatic Temperature Gradient

SUMMARYThe following is a summary of the more important conclusions which have been put forward in this paper:—1. The Nature and Distribution of Stratus in Anticyclones.(1) Stratus clouds have an adiabatic temperature gradient below them, and a reversed gradient above them; within the cloud the gradient is usually adiabatic. The same relations hold for well-defined layers of haze.(2) On the northern and eastern sides of anticyclones there is nearly always a layer of stratus, or of haze with cloud patches; the height of this layer varies between 3000 and 6000 feet above the surface, but the level is usually the same over a very large area.(3) Stratus is common in winter on the southern sides of anticyclones.

scholarly journals 19. Convection Zones and Coronae of White Dwarfs

1971 ◽  
Vol 42 ◽  
pp. 130-135 ◽  
Author(s):  
K. H. Böhm ◽  
J. Cassinelli
Keyword(s):  
Chemical Composition ◽  
Temperature Gradient ◽  
White Dwarf ◽  
White Dwarfs ◽  
Convection Zone ◽  
Adiabatic Temperature ◽  
Turbulent Convection ◽  
Cool White Dwarfs ◽  
Adiabatic Temperature Gradient

Outer convection zones of white dwarfs in the range 5800 K ≤ Teff ≤ 30000 K have been studied assuming that they have the same chemical composition as determined by Weidemann (1960) for van Maanen 2. Convection is important in all these stars. In white dwarfs Teff < 8000 K the adiabatic temperature gradient is strongly influenced by the pressure ionization of H, HeI and HeII which occurs within the convection zone. Partial degeneracy is also important.Convective velocities are very small for cool white dwarfs but they reach considerable values for hotter objects. For a white dwarf of Teff = 30000 K a velocity of 6.05 km/sec and an acoustic flux (generated by the turbulent convection) of 1.5 × 1011 erg cm−2 sec−1 is reached. The formation of white dwarf coronae is briefly discussed.

Influence of viscous dissipation on Bénard convection

1974 ◽  
Vol 64 (2) ◽  
pp. 369-374 ◽  
Author(s):  
D. L. Turcotte ◽  
A. T. Hsui ◽  
K. E. Torrance ◽  
G. Schubert
Keyword(s):  
Temperature Gradient ◽  
Viscous Dissipation ◽  
Dimensionless Parameter ◽  
Finite Amplitude ◽  
Adiabatic Temperature ◽  
Numerical Calculations ◽  
Bénard Convection ◽  
Benard Convection ◽  
Adiabatic Temperature Gradient ◽  
Flow Velocities

The approximations implicit in Bénard convection have been modified to include viscous dissipation. It is shown that both the influence of an adiabatic temperature gradient and of viscous dissipation are governed by the same dimensionless parameter Di = αgh/cp. Numerical calculations of finite amplitude convection are given for finite values of Di. It is found that increasing Di decreases flow velocities and finally stabilizes the flow.

scholarly journals Self-Consistent Thermodynamic Parameters of Diopside at High Temperatures and High Pressures: Implications for the Adiabatic Geotherm of an Eclogitic Upper Mantle

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1322
Author(s):  
Chang Su ◽  
Dawei Fan ◽  
Jiyi Jiang ◽  
Zhenjun Sun ◽  
Yonggang Liu ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Thermodynamic Parameters ◽  
Upper Mantle ◽  
High Pressures ◽  
Potential Temperature ◽  
Theoretical Data ◽  
Adiabatic Temperature ◽  
Depth Range ◽  
Self Consistent ◽  
Adiabatic Temperature Gradient

Using an iterative numerical approach, we have obtained the self-consistent thermal expansion, heat capacity, and Grüneisen parameters of diopside (MgCaSi2O6) over wide pressure and temperature ranges based on experimental data from the literature. Our results agree well with the published experimental and theoretical data. The determined thermodynamic parameters exhibit nonlinear dependences with increasing pressure. Compared with other minerals in the upper mantle, we found that the adiabatic temperature gradient obtained using the thermodynamic data of diopside is larger than that of garnet while lower than that of olivine, when ignoring the Fe incorporation. Combining our results with thermodynamic parameters of garnet obtained in previous studies, we have estimated the adiabatic temperature gradient and geotherm of an eclogitic upper mantle in a depth range of 200–450 km. The results show that the estimated adiabatic temperature gradient of the eclogite model is ~16% and ~3% lower than that of the pyrolite model at a depth of 200 km and 410 km, respectively. However, the high mantle potential temperature of the eclogite model leads to a similar temperature as the pyrolite model in a depth range of 200–410 km.

scholarly journals Boussinesq convection in a gaseous spherical shell

2019 ◽  
Vol 82 ◽  
pp. 373-382
Author(s):  
L. Korre ◽  
N. Brummell ◽  
P. Garaud
Keyword(s):  
Temperature Gradient ◽  
Boundary Conditions ◽  
Spherical Shell ◽  
Mixed Boundary ◽  
Mixed Boundary Conditions ◽  
Boussinesq Approximation ◽  
Fixed Temperature ◽  
Planetary Interiors ◽  
Adiabatic Temperature Gradient ◽  
Relevant Quantity

In this paper, we investigate the dynamics of convection in a spherical shell under the Boussinesq approximation but considering the compressibility which arises from a non zero adiabatic temperature gradient, a relevant quantity for gaseous objects such as stellar or planetary interiors. We find that depth-dependent superiadiabaticity, combined with the use of mixed boundary conditions (fixed flux/fixed temperature), gives rise to unexpected dynamics that were not previously reported.

Convective Overshooting in Extreme Horizontal-branch Stars Using MESA with the k-omega Model*

2021 ◽  
Vol 923 (2) ◽  
pp. 166
Author(s):  
Zhi Li ◽  
Yan Li
Keyword(s):  
Temperature Gradient ◽  
Outer Boundary ◽  
Horizontal Branch ◽  
Convective Boundary ◽  
Sdb Stars ◽  
Horizontal Branch Stars ◽  
Convective Core ◽  
Three Stages ◽  
Omega Model ◽  
Adiabatic Temperature Gradient

Abstract To explore overshoot mixing beyond the convective core in core helium-burning stars, we use the k−ω model, which is incorporated into the Modules of Experiments in Stellar Astrophysics to investigate overshoot mixing in the evolution of subdwarf B (sdB) stars. Our results show that the development of the convective core can be divided into three stages. The mass of the convective core increases monotonically when the radiative temperature gradient, ∇rad, monotonically decreases outwardly, and overshoot mixing presents an exponential decay similar to Herwig. The splitting of the convective core occurs repeatedly when the minimum value of ∇rad near the convective boundary is smaller than the adiabatic temperature gradient, ∇ad. The mass at the outer boundary of the convective shell M sc can exceed 0.2 M ⊙ after the central helium abundance drops to about Y c ≈ 0.45. It is close to the convective core masses derived by asteroseismology for younger models (0.22 to ∼0.28 M ⊙). In the final stage, “core breathing pulses” occurred two or three times. Helium was injected into the convective core by overshoot mixing and increased the lifetime of sdB stars. The mass of the mixed region M mixed can rise to 0.303 M ⊙ by the end. The oxygen content in the central core of our g-mode sdB models is about 80% by mass. The high amounts of oxygen deduced from asteroseismology may be evidence supporting the existence of core breathing pulses.

Sign in / Sign up

Export Citation Format

Share Document