Atmospheric Turbulence Parameters Research Articles

Oxidation of nitric oxide controlled by turbulent mixing in plumes from oil sands extraction plants

Results are presented of airborne measurements taken in oil sands extraction plant plumes in Fort McMurray, Alberta, Canada. Measurements with fast response monitors at a high sampling rate illustrate the narrow reaction zone in the plume caused by a turbulent diffusion reaction of NO to NO 2 as suggested by theoretical and laboratory studies. The measured conversion rates of NO to NO 2 varied considerably from day to day, from 0.2 to 21.4% min −. Analysis of the oxidation rate of NO to NO 2 and of the atmospheric turbulence parameter reveals that, over the distances and time scales within which the plumes are distinguishable from the background, the nitrogen oxides chemistry in the plumes is controlled by the rates at which the plumes mix with the ambient air (containing ozone), rather than by chemical kinetics.

Measurement and modeling of scintillation intensity to estimate turbulence parameters in an Earth-space path

The theoretical and experimental aspects of the analysis of amplitude scintillations as a possible practical remote-sensing tool of atmospheric turbulence parameters with special emphasis on earth-space paths are explored. Theoretical studies and experimentation reveal that the scintillation variance when complemented with spectral analysis and suitable modeling of the path leads to realistic values of the parameters. A layered turbulent structure has been studied in particular, the strategy of data analysis is given in detail, and the limitations due to the cross-path wind profile are discussed.

Use of Doppler radar for the measurement of atmospheric turbulence parameters from the intensity of clear‐air echoes

Doppler radars measure the refractivity turbulence structure constant Cn2 in a straightforward manner. In this paper we explore the relationship between Cn2 and the intensity of atmospheric turbulence as parameterized by the eddy dissipation rate ε. We develop some tentative relations between mean Cn2 and mean ε within the framework of inertial range turbulence theory, taking into account the intermittent nature of atmospheric turbulence. These relations permit the estimation of mean ε from radar observations alone. The analysis is applied to the determination from Sunset radar data of vertical profiles and time‐height contours of mean ε.

Atmospheric Turbulence Parameters Deduced from Radiosonde Measurements and Spectral Analysis of Los Fading

The paper presents evaluation of atmospheric turbulence parameters (necessary for the design of tropospheric-scatter communication links and radar target identification and imaging resolution) from two different-indirect techniques. One method utilizes routine radiosonde observations: an empirical correlation between Vāisālā—Brunt frequency (a measure of thermal atmospheric stability and so deduced from radiosonde measurements) and refractive index fluctuations-spectral shape (slope) has been developed by Gjessing et al. It has been used to compute spectral slope over-different regions of the Indian sub-continent. The other method is through spectral analysis of tropospheric propagated signal fading. Spectral analysis of fading on a line-of-sight link between Delhi and Sonepat (LOS path ~42 km, frequency ~7.6 GHz) has been performed under varied meteorological conditions. Spectral slope is observed to be a characteristic representation of atmospheric structures present in the medium, and spectral intensity enables to determine Tatarskii's structure parameter Cnn2.

Sodar studies of the thermal structure of the lower Troposphere at Delhi

The monostatic sodar system set up at National Physical Laboratory has been operating continuously to study the thermal structure of the lower troposphere upto a vertical height of 350 m. The results obtained from December 1914 through April 1975 a-re presented. The observed structures showing thermal plumes, inversions, instabilities, turbulences etc developing in the atmosphere as a function of space and time have been indexed to indicate the type of meteorological conditions expected for anyone of these indices. To examine if the sodar can be used for 24 hours monitoring of atmospheric refractivity gradients, the intensity of the received echo signal a-t a fixed height of 150 m ha-s been measured using a microphotometer and compared with the refractivity gradient number obtained from radiosonde data. The results show that the two techniques have a good correlation within the limits of the experimental error. These relative values of received intensity have also been used to calculate thermal structure function CT. The computed values of a p have been found to compare well with Panofsky observations, showing, thereby the utility of the sodar echograms to derive information of the atmospheric turbulence parameter.

Monsoon squalls over Thumba during the year 1966

In this paper monsoon squall is considered as distinct from thunder squall of low wind speed and is defined as the sudden increase in wind speed to 15kt or more with less than 25° change indirection. The main features of such squalls recorded at Thumba by the electrical anemographs at three different altitudes (58,136 and 200ft)during the monsoon season of 1966 are discussed with reference to their diurnal variation, duration, speed and direction.
 
 The monsoon squall data has been analysed and scatter diagrams of mean squall wind profiles upto 200 ft height have been constructed, The mean vertical wind shears in two different layer3 136-58 ft and 200-136 ft under squally weather conditions are described with the help of shear vector diagrams. The mean vertical shear does not exceed 5 kt/30m. Monsoon squall wind veers with height.
 
 The wind in the layer 58-200 ft is found to obey the power law-
 u/u1 = (z/z1)p
 
 under squally weather conditions. The computed values of power index p=0.115 and the atmospheric turbulence parameter n=0.2 are described briefly.

Measurements of the propagation component of radar tracking noise at a wavelength of 3cm

Measurements have been made of the angular propagation noise and amplitude scintillations on a 15km overland path at 1° elevation in northern England. They indicate r.m.s. deviations in angle of arrival ranging between 1" and 10" (4.8–48μrad) for aerials of 2m aperture during one year's observations. The propagation noise (short-term angle-of-arrival fluctuation) spectrum falls rapidly with increasing frequency and is negligible at frequencies above 1 Hz for this aerial aperture. Little correlation is apparent between the magnitude of the effects and changes in atmospheric humidity, but the r.m.s. level is approximately proportional to mean air temperature (in degC). Autocorrelation analysis on a single path, and crosscorrelation analysis on two adjacent paths, indicate a mean scale of turbulence of about 15m for an inclined path extending from 5 to 300m above the surface. Amplitude scintillations of the received signal give a similar power spectrum to that of angular propagation noise, and a general level of power change of the order of 0.1 dB is observed. The results are similar to those obtained by workers in the USA, and are in fair agreement with theory, although the scarcity of information on atmospheric-turbulence parameters at heights below 300m, and the use of an inclined path, make accurate comparison with theory difficult.

Turbulent Atmospheric Parameters by Contaminant Deposition

Abstract Many contaminant or smoke-puff experiments have been performed in the atmosphere to determine certain significant parameters of atmospheric turbulence. This paper presents a reanalysis of some of these experiments, using a technique suggested by Frenkiel and Katz. The results show that the similarity theory of Batchelor, as suggested by Gifford, and the, subsequent theory of Lin, explain atmospheric turbulence for the case of low wind shears. Turbulent dispersion in the presence of high wind shears, however, follows the diffusion relation theorized by Tchen. Values for ϵ, the rate of eddy-energy density dissipation per unit mass, are measured, substantiating some of Gifford's estimates; also measured are the universal and absolute constants C1, and α respectively, of Batchelor, and u2 the turbulent energy density per unit mass, which are compared to some measurements of Frenkiel and Katz, and of Kellogg.