A New Method to Retrieve the Diurnal Variability of PBLH from Backscatter Lidar under Different Thermodynamic Stabilites

Strongly influenced by thermodynamic stability, the planetary boundary layer height (PBLH) is an important parameter for understanding the accumulation of pollutants and dynamics of the lower atmosphere. Backscatter lidar measures the vertical distribution of aerosol with high spatiotemporal resolution, offering a great potential for continuously tracking daytime PBLH. In this study, the PBLH retrieved from lidar for stable boundary layer (SBL), neutral boundary layer (NBL), and convective boundary layer (CBL) are systematically investigated, based on an intensive 8-year dataset of micropulse lidar and radiosonde measurements at the ARM Southern Great Plains research site. Due to weak thermal convection and complex aerosol stratification, traditional gradient and wavelet methods cannot fully capture the diurnal variability of the PBLH under SBL. Consequently, a new method, namely “DTDS”, based on the vertical properties and temporal variance of PBLH is developed to accurately retrieve the PBLH under different thermodynamic stability. Relying on a physical interpretation of PBL development, different selection schemes are applied to the various PBLH stages, which are growth, maintenance, and decline periods respectively. The morning radiosonde would serve as input, and constrain the initial position of PBLH retrievals. Comprehensive evaluation of this DTDS method highlights improved correlation with radiosonde results for SBL and reduced absolute biases for both SBL and CBL. Compared with the existing retrieval algorithms, the PBLHs derived from DTDS show strong consistency with radiosonde diurnal cycles, and demonstrate significantly smaller biases under various pollution levels. The DTDS method would be useful for studying the interaction between PBL and aerosols under different thermodynamic conditions, which should thus be of interest to both lidar and aerosol communities.