Estimate of boundary-layer depth over Beijing, China, using doppler lidar data during SURF-2015

Using six fair-weather days of lidar and tower data under clear to cloudy skies, we evaluate the ability of the Doppler lidar to probe the urban boundary-layer structure, and then propose a composite method for estimating the diurnal cycle of the PBL depth using the Doppler lidar.

For the convective boundary layer (CBL), a threshold method using vertical velocity variance is used, since it provides more reliable CBL depths than a conventional maximum wind-shear method. The nocturnal boundary-layer (NBL) depth is defined as the height at which decreases to 10 % of its near-surface maximum minus a background variance. The PBL depths determined by combining these methods have average values ranging from 270 to 1500 m for the six days, with the greatest maximum depths associated with clear skies.