A New Image Compensation and Segmentation Algorithm to Retrieve Atmospheric Boundary Layer Height for LiDAR RHI 2-D Scan

The atmospheric boundary layer controls surface-atmosphere energy and matter exchange, and plays a central role in air pollution and weather dynamics. However, conventional vertically pointing LiDAR observations suffer from a near-surface blind zone and cannot provide 2-D information on aerosol distributions, limiting their capability to resolve delicate spatial structures and capture the evolution of the boundary layer. To overcome this limitation, this study employed LiDAR range-height indicator (RHI) scanning to obtain 2-D aerosol observation data with no blind zones and high spatiotemporal resolution. Based on the characteristics of RHI image data, we propose an image compensation and segmentation algorithm (ICSA) for detecting the atmospheric boundary layer height (ABLH). The algorithm compensates for the RHI backscatter signal to more accurately represent aerosol concentration and incorporates Otsu's multithreshold segmentation and connected-component analysis. It offers a new approach to accurately characterize the boundary layer structure and evolution. The proposed algorithm can stably retrieve the ABLH without a predefined height range, and when a predefined height constraint is applied to the gradient method (GM) and STRATfinder methods, the ABLH results from the three methods are generally consistent. Two additional cases further verify the effectiveness of the proposed algorithm in identifying the ABLH during complex boundary layer evolution. The results demonstrate that the method can accurately capture structural variations of the atmospheric boundary layer associated with turbulent mixing and convective transport within the wind field. It also clearly depicts the redistribution process of aerosols under the intermittent turbulent effects induced by near-surface temperature inversions. These cases not only demonstrate the algorithm's exceptional capability to resolve the fine structure of the atmospheric boundary layer but also provide a reliable pathway to deeper insights into the coupled dynamic-thermal mechanisms within the near-surface layer.