Biomass burning aerosol transport from Indo-China Peninsula to South China: fluorescence lidar observation and analysis

Abstract. South China, a densely populated region frequently affected by transported biomass burning aerosol (BBA), requires sensitive remote sensing observations to characterize these plumes. Laser-induced fluorescence (LIF) lidar is a powerful tool for detecting fluorescent aerosol and has recently been demonstrated effective in identifying transported BBA over Europe, while its applications in South China remain scarce. Here, we present LIF lidar observations of fluorescent aerosol conducted at Nanping, South China. The detected fluorescent layer was relatively weak, with a fluorescence signal intensity more than two orders of magnitude lower than the N2 Raman signal intensity (maximum spectral fluorescence backscatter coefficient ≈0.16×10-5 Mm−1 sr−1 nm−1). Nevertheless, it showed a distinct spectral signature compared with typical urban aerosol. Integration of multi-source datasets suggests that the long-range transported BBA emitted by weak fire activity in the Indo-China Peninsula (ICP) was a major contributor to the fluorescent layer. Furthermore, the concurrent presence of BBA and enhanced water vapor indicated a humid environment favorable for aerosol processing. Consistent with the high sensitivity of LIF lidar reported in previous studies, our observations show that weak, long-range transported BBA from the ICP can be observed over South China during periods of relatively weak fire activity, thereby offering new insights into their transport mechanisms and potential environmental impacts.