Clouds and Meteorological Effects on Bioaerosol Particles: Insights From the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE)

Abu Sayeed Md Shawon, KATHERINE BENEDICT, Kyle Gorkowski, Ryan Farley, Nevil Franco, James E. Lee, Manvendra Dubey, Lynn M. Russell, Allison Aiken, Los Alamos National Laboratory

     Abstract Number: 53
     Working Group: Bioaerosols

Abstract
In addition to their impact on local ecosystems and human health, bioaerosol - such as bacteria, pollen, and fungal spores - can modify cloud properties when activated as cloud condensation nuclei (CCN). To investigate the interaction between clouds and bioaerosol particles near a coastal city, during the EPCAPE Partitioning Thrust by Los Alamos National Laboratory (EPCAPE-PT-LANL), we deployed a ground-based virtual impactor (GCVI, Brechtel) and a wideband integrated bioaerosol sensor (WIBS-5, DMT) at Mt. Soledad (La Jolla, California) from October 20, 2023, to December 04, 2023. Under cloudy conditions, we collected cloud droplets using the GCVI and subsequently dried them. These dried cloud droplets represent the cloud droplet residuals. We compared the bioaerosol present in cloud residual with the cloud-free periods with the aerosol inlet Bioaerosols were measured using the WIBS that excites fluorescence particles larger than 0.5µm and smaller than 30µm in two wavelengths and measures the emission from these excited particles in two different wavebands. The specific excitation/emission wavelengths are optimized for detecting bioaerosol particles that fluoresce, commonly referred to as fluorescent bioaerosol particles (FBAPs). During the deployment, the number concentration of FBAPs reached as high as ∼5 particles/cc and did not exhibit any diurnal variation for the total or by type. Within the size range of the WIBS, approximately 30% ± 10% of total particles were FBAPs, regardless of cloud presence. Although there were no apparent differences in the FBAP fraction, the absolute number concentration of FBAPs and the relative abundance of different types of FBAPs varied between cloud and no-cloud conditions, indicating that different FBAP types may be more prevalent in stratocumulus formation observed over land near the coast in the eastern Pacific. In our presentation, we will also delve into how meteorological factors such as temperature, relative humidity, etc., influenced the properties of FBAPs.