Diurnal Dynamics of the Reduced Turbulent Kinetic Energy of in the Atmospheric Boundary Layer from Minisodar Measurements

Abstract

Based on acoustic remote measurements of the diurnal dynamics of three wind velocity components and their variances in the lower 200-meter layer of the atmosphere, the kinetic energy of the atmosphere reduced to unit mass is estimated, with a particular emphasis on the turbulent kinetic energy component. For a 24-h period of continuous minisodar observations, the turbulent energy in the surface layer was very low to altitudes of ~50 m. With increase in altitude from 50 to 100 m, the turbulent kinetic energy quickly increased, and at altitudes exceeding 100 m, its fast growth is observed, with a maximum at altitudes of 150-200 m. Essential influence of time of the day on the results of observations was established. Thus, at night at the same altitudes the kinetic energy density first did not exceed 20 J/kg, and its moderate growth (from 20 to 50 J/kg) was observed with increasing time. In the morning, the maximum energy density of air masses was observed. After sunrise, the turbulent component of the kinetic energy density rapidly decreased. It is essential that the system the Earth surface-the near-ground air layer tends to an equilibrium state. As a consequence, the spread of values of the turbulent energy is reduced. The most significant changes were observed at altitudes in the range 100-200 m. It is essential that at altitudes up to 50-100 m, time of the day had no significant effect, because at these altitudes the turbulent energy was low and remained practically unchanged with time. Irrespective of time of the day, the maximum turbulent energy was observed at altitudes in the range 100-200 m that pose the greatest danger to small flying objects. The corresponding estimations are presented.

Dynamics of total kinetic energy components in the atmospheric boundary layer from minisodar measurements

“…The vertical resolution of minisodars 12 can reach 5 m with time averaging, as a rule, from 1 to 30 min. Results of our preliminary analysis 11,13 of the spatiotemporal dynamics of the kinetic energy in the ABL from data of minisodar measurements have confirmed the efficiency of the proposed approach.…”