scholarly journals Turbulence and diffusion in the lower atmosphere

1946 ◽  
Vol 186 (1004) ◽  
pp. 20-35 ◽  
Keyword(s):  
Water Vapour ◽  
Atmospheric Turbulence ◽  
Classical Theory ◽  
Quantitative Approach ◽  
Lower Atmosphere ◽  
Mixing Length ◽  
Self Consistent ◽  
Consistent Treatment ◽  
And Diffusion ◽  
Turbulence And Diffusion

The only existing theory of atmospheric turbulence which is capable of giving a quantitative approach to the complex problems of diffusion in the lower atmosphere is the classical theory in which it is generally assumed that the effect of eddies in the atmosphere is completely analogous to that of molecules in a gas apart from a difference of scale. This assumption, which later evidence has shown to be incorrect, is not essential to the theory, and in the present paper is replaced by the assumption that the mixing length of an eddy increases with both height above and nature of the earth’s surface . With this assumption a self-consistent treatment of diffusion is developed which is able to account quantitatively for such meteorological phenomena as the distribution of water vapour over land and sea (including evaporation from the oceans) and the diffusion of smoke near the ground. The treatment is mainly confined to diffusion in an adiabatic atmosphere.

scholarly journals Turbulence and diffusion in the lower atmosphere with particular reference to the lateral effect

1947 ◽  
Vol 190 (1021) ◽  
pp. 232-244 ◽  
Keyword(s):  
Atmospheric Turbulence ◽  
Lower Atmosphere ◽  
Saturated Liquid ◽  
Lateral Component ◽  
Vapour Concentration ◽  
Parabolic Shape ◽  
Rate Of Decay ◽  
Experimental Values ◽  
And Diffusion ◽  
Turbulence And Diffusion

It has been established experimentally by Pasquill that the theory of atmospheric turbulence put forward by O. G. Sutton in 1934 leads to satisfactory theoretical rates of evaporation from plane, saturated, liquid surfaces. The theory, however, overestimates the vapour concentration at any point and underestimates the rate of decay of concentration with height above such evaporating surfaces of finite lateral dimensions. In the present paper it is suggested that one of the reasons for this discrepancy lies in the neglect of the lateral component of turbulence. The aim of the present investigation is to estimate quantitatively the effect on the values of the theoretical vapour concentration produced by the introduction of a lateral component of turbulence. It is shown that the theoretical evaporation is not appreciably affected by the modification introduced but that the concentration of vapour, and the rate of decay of concentration with height, are much nearer the experimental values, which, however, are very scanty. The investigation deals with a saturated area of parabolic shape. Extensions of the theory are contemplated.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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