The planetary boundary layer (PBL) and its associated entrainment zone are important features in the thermodynamic structure of the lower troposphere, but they may be easier to detect by their effect on aerosol and clouds than by thermodynamic profiling of the atmosphere. NASA's Micro-pulse Lidar Network (MPLNET) supports ground-based lidar observations at a number of sites across the globe, some of which have operated continuously for years. With an algorithm for automated PBL detection based on the backscatter gradient, this data makes it possible to observe the diurnal development and seasonal variability of the PBL height with a temporal resolution of minutes. Such information is useful for understanding aerosol transport and interaction between aerosol and the PBL.

The PBL detection algorithm combines the wavelet covariance transform approach proposed by Davis et al. (2000) and Brooks (2003) with an iterative curve-fitting process from Steyn et al. (1999). The former method provides a first guess for the latter which is adaptable to a wide range of climates and weather conditions; the latter method refines the PBL height and adds an estimate of entrainment zone depth. The results are months-long climatologies of PBL behavior at MPLNET sites across the globe, verifiable by radiosonde data, with estimations of the entrainment occurring between the mixed layer and free troposphere.