Stratospheric Turbulence and Vertical Effective Diffusion Coefficients PDF Download
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Author: N. W. Rosenberg
Publisher:
ISBN:
Category : Atmosphere, Upper
Languages : en
Pages : 20
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Book Description
Author: N. W. Rosenberg
Publisher:
ISBN:
Category : Atmosphere, Upper
Languages : en
Pages : 20
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Book Description
Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Atmospheric models
Languages : en
Pages : 36
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Book Description
Vertical transport in the stratosphere occurs by many processes and the question of the relative importance of stratified turbulence is considered in the context of a 'vertical stack model' described in a previous report. The 'vertical stack model' was designed to estimate the effect of intermittent turbulent layers (separated by essentially laminar flow) and it is here examined in some detail. In particular, a number of less obvious implications are discussed and a list of experimental tests of the model is suggested. It is concluded that the rate of turbulence for vertical transport in the stratosphere remains an open question.
Author: S. P. Zimmerman
Publisher:
ISBN:
Category : Atmospheric models
Languages : en
Pages : 22
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Book Description
The determination of winds and temperature by rawinsonde allows us to calculate the Richardson number, a measure of atmospheric instability. From this, we can then determine the turbulent atmospheric parameters, diffusivity (K), rate of heat deposition (epsilon), and the vertical turbulent intensity (w2). Comparison of these data, for the spring periods, with contours of residual stratospheric radioactivity demonstrate that, at the tropopause, the isocountours of turbulent diffusivity accurately follow the isodensity contours of the residual radioactivity. We also demonstrate that the rapid cessation of the turbulent diffusivity accurately predicts the level of the tropopause. (Author).
Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Stratosphere
Languages : en
Pages : 36
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Book Description
Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Atmospheric circulation
Languages : en
Pages : 36
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Book Description
This paper reviews the estimates to date of the vertical 'effective diffusion coefficient' for stratospheric small scale turbulence transport, KB. These estimates range (in order of magnitude) from 1.0 sq. meter/s to 0.01 sq. meter/s, that is to say from a value which would make turbulence a dominant factor in stratospheric transport to a value which would make it totally insignificant. Such a large range implies much ignorance in this subject. The various techniques are closely examined and the unanswered experimental questions are exhibited. The conclusion is reached that more experimental work needs to be done before one has a reliable estimate for KB.
Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Computer simulation
Languages : en
Pages : 54
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Book Description
A self-consistent method of characterizing vertical turbulent transport by means of a diffusion parameter is demonstrated for the extremely inhomogeneous case of layered turbulence in a stratified fluid. Between the horizontal turbulent layers, horizontal laminar flow is assumed to occur, and molecular diffusion is ignored. The layers are assumed to occur at random heights with random thickness. An analogy is made between the process of random mixing layers and the finite difference representation of the diffusion equation. It is demonstrated by means of a series of digital computer experiments that, in the case where total mixing takes place within the turbulent layers, the diffusion parameter herein developed is the valid one to use (in contrast to 'eddy diffusivity'). The relation between this inhomogeneous diffusion parameter and practical experimental measurements is given. The motive behind this investigation involves vertical transport of pollution in the environment in general and in the stratosphere in particular.
Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 58
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Book Description
This paper is motivated by the requirement to improve understanding of vertical motion of pollutants in the stratosphere. One method to estimate vertical transport due to the effects of turbulence is by means of the effective diffusivity coefficient. To calculate this parameter, it is often necessary to know the value of epsilon, the rate of turbulent dissipation. This parameter, epsilon, is also important to know in the context of the global numerical stratospheric simulation models now being created for environmental assessment purposes.
Author: Anthony J. Broderick
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 684
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Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 76
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Book Description
This report is a tutorial on the effects of atmospheric turbulence upon systems which rely upon the propagation of LASER beams. In addition to providing a simplified presentation of turbulence theory and optical effects, it describes the state of the art of the new technique of radiosonde estimation of index of refraction fluctuations. Suggestions are given for future research which will help to answer current Air Force needs. The feasibility of some laser systems will depend upon the value of r0, the coherence length (which is related to “C2n” which in turn is related to the degree of turbulence). At present, the statistics of “r0” are inadequate.
Author: Edmond M. Dewan
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 44
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Book Description
What are the theoretical and experimental physical differences between waves and turbulence? The motivation behind this question is related to the practical problems associated with laser beam propagation and pollution transport in the atmosphere. Because turbulence causes mixing and waves do not, one must not regard turbulence as a field of random waves. The power density spectrum of velocity fluctuations, when taken along, cannot be used to distinguish between waves and turbulence. Its physical interpretation can differ radically depending upon which type of motion is involved. Two approaches are used here to differentiate theoretically and experimentally between waves and turbulence. The first involves the degree of interaction between modes. The second approach depends on the mixing property of turbulence.
