Spectral composition of temperature turbulence for various stratification types of the surface air layer
D.A. Marakasov, A.L. Afanasiev, E.V. Gordeev
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: non-Kolmogorov turbulence, energy spectrum, stratification, Monin-Obukhov number, sonic weather stations
Abstract
The parameters of the spectral model of small-scale turbulence are the most important characteristics used to describe the propagation of light and sound in the atmosphere. One of the determining factors affecting the spectral composition of turbulence is the stratification regime. Based on the processing of time series of fluctuations of meteorological parameters recorded by acoustic weather stations, the effect of stratification of the surface air layer on the deviations of the turbulence spectrum from the Kolmogorov-Obukhov model is investigated. When comparing the time dynamics of the stability characteristic (Monin-Obukhov number) and the index of the power model of the spectrum of temperature fluctuations, a significant correlation between them is established. An empirical model of the dependence of the spectrum index on the stability parameter is proposed. The model makes it possible to estimate changes in the parameters of the spectral structure of small-scale turbulence based on estimates of the magnitude and direction of turbulent heat and momentum fluxes. The dependence reflects the features of generation of temperature turbulence with different stratification in the surface layer. Information on turbulent spectral parameters obtained on the basis of estimation of stratification can be further used to solve problems of propagation, of optical and acoustic as well as sounding of the atmosphere.
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