Mobile Doppler LiDAR Observations of the Convective Boundary Layer Over California

A series of transects using a truck-mounted Doppler LiDAR were conducted to obtain mobile vertical profiles of the backscatter intensity and radial velocity across California. Using the backscatter and velocity profiles, several techniques were used to estimate the depth of the convective boundary layer (CBL). The CBL was estimated from the backscatter profiles using three analyses: (1) the Haar wavelet covariance, (2) the variance, (3) the gradient. These analyses were compared to vertical velocity variance, which uses a specified threshold (0.15 m2 s-2) to determine CBL height. The accuracy of the backscatter analyses was heavily dependent on strong aerosol loading near the surface and clean air in the free-atmosphere. The accuracy of the vertical velocity variance was dependent on the variance threshold, and underestimated the CBL depth in conditions with weak vertical motions. The backscatter analyses tended to yield deeper CBL estimates on the order of 100 m compared to the vertical velocity variance analysis. Vertical velocity skewness and variance profiles differ between stationary and mobile observations, with variance profiles decreasing with height in cross-California transects. The Haar wavelet and vertical velocity variance techniques were applied to a transect with heavy smoke-aerosol loading emitted from a nearby wildfire. Observations show weak vertical mixing in regions with heavy smoke, along with suppressed CBL heights