Influence of an internal gravity wave on the shape of the curve for the spectral density of the vertical component of wind velocity
I.N. Smalikho, V.A. Banakh, A.M. Sherstobitov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: coherent Doppler lidar, wind turbulence, internal gravity wave, spectral density, exponent
Abstract
Issues of turbulent wave interaction in the atmospheric boundary layer (ABL) have not yet been sufficiently studied. In particular, the question of the influence of an internal gravity wave (IGW) arising in a thermally stable ABL on the spectrum of turbulent wind speed fluctuations remained open. In this work, using pulsed coherent Doppler lidar measurements, the influence of IGW on the shape of the curve for the spectral density of the vertical component of the wind velocity is studied. It has been established that IGW causes a significant change in the shape of the wind speed spectrum curve at frequencies below the boundary of the inertial turbulence interval. In this case, in the interval between the IGW frequency and the lower limit of the inertial interval, the frequency dependence of the spectrum is close to a power law. By analyzing 700 lidar estimates of vertical wind speed spectra, it was found that for such a frequency interval the exponent is on average equal to -3. The results of the work can be used to improve algorithms for numerical simulation of thermally stable ABL.
|
