Diurnal dynamics of the kinetic energy in the atmospheric boundary layer retrieved from minisodar measurements

Based on remote acoustic measurements of the altitude profiles of three wind velocity components in the lower 200-meter layer of the atmosphere, the kinetic energy per unit air mass and its components are estimated with particular emphasis on the turbulent kinetic energy component. An analysis of the vertical profiles of the turbulent kinetic energy E _TKE in the atmospheric boundary layer showed that in the near-surface layer at altitudes up to 50 m, its values and spread are very small and sharply increase with altitude. The maximum E _TKE values were observed at midnight, as well as the maximum kinetic energy of ordered motion E _MKE. In the morning, the contribution of the kinetic energy of average motion in the lower 100-meter layer of the atmosphere exceeded that of the turbulent kinetic energy, which can be associated with the presence of a wind shear on the corresponding wind velocity profiles. The E _MKE values increase in the morning, reach their maximum values by noon, and then decrease by midnight. During minisodar measurements, the total kinetic energy per unit air mass changed from several tens to several hundreds J/kg. The diurnal dynamics of the kinetic energy was characterized by the presence of several minima and maxima, the time of occurrence and values of which depended on the meteorological conditions of sounding, the presence and characteristics of cloudiness, and solar radiation. The most significant changes occurred at altitudes in the range 100-200 m. At altitudes up to 50-100 m, the time of day had no significant effect on the results of observations, the turbulent energy was low and remained practically independent of the time of day. At any time, the maximum turbulent energy was observed at altitudes in the range 100-200 m, which possesses the greatest danger to light flying objects. Based on the results of our analysis, the conclusion was made that during the time periods of maximum perturbations of the ordered motion (active turbulent fluxes of air masses), the linear sizes of perturbation regions are commensurable with the spatial resolution D z = 5 m of the observation method. The possibility of revealing the periods of the lowest and highest turbulence, that is, the most and least favorable time for flights of light flying objects, is illustrated.

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