Atmospheric turbulence structure above urban nonhomogeneous surface

Abstract

A new 21-meter eddy covariance tower is installed in the Meteorological observatory of Moscow State University in November 2019. It includes 3 levels with METEK sonic anemometers. The mast is located inside the urban area and makes it possible to analyze the structure of atmospheric turbulence in a heterogeneous urban condition. The measurement data from November 2019 to May 2020 are processed. Turbulent fluctuations of the wind velocity components are found to increase with height within 20 meters above the surface. The turbulent kinetic energy is proportional to the square of the averaged horizontal wind speed. The drag coefficient is determined by the type of footprint surface, with a value of 0.08 and 0.05 for urbanized and vegetated surfaces, respectively. The "turbulent flux of heat flux" is reasonably well predicted by diagnostic relation with heat flux, skewness and standard deviation of vertical speed, suggesting significant contribution of coherent structures to turbulent fluxes. The daily amplitude of the temperature variance increases with the daily amplitude of the average temperature. The paper considers the conditions for the applicability of the Monin-Obukhov similarity theory to the calculation of turbulent fluxes over a heterogeneous urban landscape.