Boundary Layer Height and Entrainment Zone Thickness Measured by Lidars and Wind-Profiling Radars

TLDR

Lidar backscatter reflects aerosol concentration, while wind profiler backscatter is sensitive to refractive index variations caused by moisture gradients and turbulence. The study uses two lidars and a radar wind profiler to measure boundary‑layer height and entrainment‑zone thickness, applying a Haar continuous wavelet transform to lidar backscatter and a standard technique to wind‑profiler data. Boundary‑layer height estimates from lidar and wind profiler agree well (correlations 0.87–0.95 during daytime convection and 0.99 between lidars), whereas entrainment‑zone thickness shows weaker agreement (≈0.6–0.8), and the wavelet‑transform method yields consistent 1‑s resolution results.

Abstract

The authors examine measurements of boundary layer height zi and entrainment zone thickness observed with two lidars and with a radar wind profiler during the Flatland96 Lidars in Flat Terrain experiment. Lidar backscatter is proportional to aerosol content (and some molecular scatter) in the boundary layer, and wind profiler backscatter depends on the refractive index structure (moisture gradients and turbulence strength). Although these backscatter mechanisms are very different, good agreement is found in measurements of zi at 1-h resolution. When the dataset is limited to daytime convective conditions (times between 1000 and 1700 LT), correlation coefficients between the profiler and each lidar are 0.87 and 0.95. Correlation between the two lidars is 0.99. Comparisons of entrainment zone thickness show less agreement, with correlation coefficients of about 0.6 between the profiler and lidars and 0.8 between the two lidars. The lidar measurements of zi make use of coefficients of a Haar continuous wavelet transform of the backscatter profile. The wind profiler measurements use a standard technique. The wavelet transform technique is shown to provide consistent results with lidar data at 1-s time resolution.