Sounding of Kelvin–Helmholtz Waves by a Turbulent Lidar: I–BSE-4 Lidar

Abstract

Atmospheric waves are of increased interest in connection with exchange processes occurring in the atmospheric boundary layer. Experimental results of sounding mesoscale Kelvin–Helmholtz waves by turbulent lidars in a stably stratified boundary layer of the atmosphere are presented. This paper presents the data of measurements by the BSE-4 lidar (532 nm), which has been working over forest-steppe for a long time. Atmospheric waves in most cases were observed in the evening and at night in the range of heights from the land to 600 m, when the Richardson number in the surface air layer did not exceed a critical value of +1/4. Fourier analysis of the time series of the structural characteristic of the refractive index \(C_{n}^{2}\) shows that the spectrum of the wave process in the atmospheric boundary layer consists of a set of monochromatic waves with different oscillation frequencies. During the observations, the period of the waves varied from 1 to 11 min, and their amplitude changed from 20 to 300 m. It is found that monochromatic waves exist from half an hour to two hours. The disappearance of some monochromatic waves is compensated by the appearance of new ones. The process of generating small-scale turbulence runs throughout the life cycle of a Kelvin–Helmholtz wave. The experimental results indicate that the turbulent lidar is a sensitive device ensuring remote detection and observation of atmospheric waves.