Profiling pollen and biomass burning particles over Payerne, Switzerland using laser-induced fluorescence lidar and in situ techniques during the 2023 PERICLES campaign

Abstract. Vertical profiles of pollen and biomass burning particles were obtained at the MeteoSwiss station of Payerne (Switzerland) using a novel multi-channel elastic-fluorescence lidar combined with in situ measurements during the spring 2023 wildfires and pollination season during the PERICLES (PayernE lidaR and Insitu detection of fluorescent bioaerosol and dust partiCLES and their cloud impacts) campaign. This original approach provided, for the first time in this region, reliable information on pollen speciation aloft, bridging the gap between ground-based sampling and remote sensing observations. Pollen particles were detected near ground (up to 2 km height), showing strong fluorescence backscatter coefficients (bF) (up to 8×10-4 Mm−1 sr−1). Smoke plumes from Canada and Germany were detected at higher altitudes (3–5 km) with lower bF values compared to those from pollen particles near ground. In situ measurements and in vivo fluorescence spectra were used to classify pollen particles near ground. Ice nucleating particle (INP) concentrations relevant for mixed-phase clouds were enhanced at warm temperatures, characteristic of the contribution of biological particles to the INP population. This was further supported by the correlation between INPs at −14 °C and fluorescent bioaerosol particles detected by the Wideband Integrated Bioaerosol Sensor, while INPs at −20 °C were more strongly linked to coarse-mode dust. Comparison of bF values from two European Laser Induced Fluorescence lidar stations revealed that aged air masses containing smoke particles exhibited ∼ 50 % lower fluorescence during long-range transport in the free troposphere, possibly due to photochemical aging, mixing with non-fluorescent particles and dispersion.