Clustering of weak fluorescence spectra from bioaerosol in air using laser-induced fluorescence lidar

Laser-induced fluorescence (LIF) lidar is the main method in bioaerosol remote detection. However, its current applications are limited to specific scenarios due to weak fluorescence signals in ambient environments. In this paper, a spectrally resolved lidar system based on LIF spectroscopy was developed for bioaerosol detection. This lidar system was deployed at an elevation angle of 30° in Nanping City, Fujian Province, China from April to July 2024. During observation, weak fluorescence was detected, and its spectral contamination risk by the N₂ Raman signal was discussed and resolved. In this paper, we introduced a clustering method to process and analyze the weak fluorescence spectra. This method successfully separates fluorescence spectra into 3 clusters under weak fluorescence intensities. The possible types of each cluster are discussed and inferred based on their spatiotemporal distribution combined with backtrajectory results and meteorological data. This method enables aerosol classification even under weak fluorescence intensities, providing a new approach to atmospheric aerosol analysis.