Dynamic Aerosol Characteristics Surrounding Storms Observed in Northern Colorado During the BACS-I and BACS-II Field Campaigns

Russell Perkins, Ben Ascher, Tyler Barbero, Noelle Bryan, Charles Davis, Paul DeMott, Jacob Escobedo, Nick Falk, Janeshta Fernando, Teresa Feldman, Sean Freeman, BRIAN HEFFERNAN, Thomas C. J. Hill, Sonia Kreidenweis, Gabrielle Leung, Chamari Mampage, Allie Mazurek, Claudia Mignani, Daniel Veloso-Aguila, Christine Neumaier, Marina Nieto-Caballero, Lexi Sherman, Susan van den Heever, Leah Grant, Elizabeth Stone, Colorado State University

     Abstract Number: 454
     Working Group: Aerosol-Ecosystem Interactions

Abstract
Aerosol particles impact the properties of clouds through their roles as Cloud Condensation Nuclei (CCN) and Ice Nucleating Particles (INPs). CCN allow for the formation of cloud droplets at a critical supersaturation value that depends on particle size and hygroscopicity. CCN that activate at low supersaturations are very rare, but may be important for precipitation initiation and fog formation. INPs allow for freezing of supercooled liquid cloud droplets warmer than their homogeneous freezing temperatures around -38°C. INPs are exceptionally rare, especially at modest supercooling. Biological aerosol particles (bioaerosols) are less abundant than mineral dust aerosol in most terrestrial settings, but can be excellent low-supersaturation CCN and generally dominate populations of warm-temperature INPs. Bioaerosol release can be controlled by environmental conditions, such as rainfall, wind, temperature, and humidity, or combinations of these, such as during a cold pool passage. These mechanisms together create the possibility for feedbacks between bioaerosols and convective cloud systems, where bioaerosol ingestion into clouds alters cloud properties and precipitation.

These bioaerosol-cloud system feedbacks were the focus of the BioAerosols and Convective Storms phase I and II (BACS-I and BACS-II) field campaign which occurred in spring 2022 and 2023 at the USDA-ARS Central Plains Experimental Range (CPER) site in northern Colorado. An extensive suite of aerosol and thermodynamic measurements were employed, collocated with the NSF National Ecological Observing Network (NEON) flux tower at the CPER site. Instrument packages were deployed on the ground, the tower top, and on multirotor drones during each 4-5 week campaign. Measurements include environmental observations, aerosol, bioaerosol, CCN and INP distributions, chemical tracer analysis, airborne DNA sequence analysis, and thermodynamics and dynamics of storm and cold pool passages. This presentation will include an overview of the field campaign and highlight preliminary results of changes to aerosol distributions, populations, and properties with storm passage.