Elucidating the atmospheric boundary layer turbulence by combining UHF radar wind profiler and radiosonde measurements over urban area of Beijing

Abstract

The knowledge of atmospheric turbulence over urban environment remains limited albeit its great importance for air pollution and convection initiation. This study investigates turbulence characteristics in boundary layer based on concurrent radar wind profiler (RWP) and radiosonde observations for the year 2019 at an urban site in Beijing, China. The eddy dissipation rate (ϵ) is retrieved based on Doppler spectral width measurements from RWP. The radiosonde measurements are utilized for estimating the Brunt–Väisälä frequency which is further collocated with RWP based ϵ retrievals for the estimation of vertical eddy diffusivity, outer scale length and inner scale length profiles. Contrasting seasonality is revealed in diurnal cycle of height-resolved turbulence parameters over Beijing. Within the lowermost 1 km altitude, ϵ is estimated to be more than 10−2 m2s−3 during all seasons (except for winter), which possibly represents the highly turbulent state of the atmosphere near ground surface due to the local mountain-plain flow variation. However, above 1 km altitude, the ϵ magnitude varies between 10−4 and 10−2 m2s−3. The vertical eddy diffusivity is found to be higher in the spring and summer seasons while being approximately an order of magnitude lower in the autumn and winter seasons, which agrees with few existing studies.