Investigating the Vertical Variability of Aerosol Composition, Morphology and Mixing State over Crested Butte Mountain: Impacts on Ice Nucleation

NURUN NAHAR LATA, Jessie Creamean, Thomas C. J. Hill, Russell Perkins, Sonia Kreidenweis, Zezhen Cheng, Darielle Dexheimer, Alexander Laskin, Paul DeMott, Daniel Feldman, Swarup China, Pacific Northwest National Lab

     Abstract Number: 521
     Working Group: Aerosols, Clouds and Climate

Abstract
Aerosol particles in the atmosphere can serve as ice nucleating particles (INPs) and initiate ice crystal formation, leading to cloud formation and precipitation. The composition and mixing state of aerosol particles can affect their ice nucleation (IN) potential, making it essential to understand their vertical variability. This study investigated the vertical variability of aerosol particle composition and its relationship to INP characteristics. The aerosol particles were sampled during July 2022 using a Size and Time-resolved Aerosol Collector (STAC) platform and an “IcePuck” filter sampler deployed with tethered balloon system (TBS) at the US Department of Energy's Atmospheric Radiation Measurement Program's primary site at Crested Butte Mountain at an elevation of 2886 meters during the Surface Atmosphere Integrated Field Laboratory (SAIL) study for offline chemical and IN analysis, respectively. Filter samples are being used to probe the freezing properties of the particles using the CSU Ice Spectrometer, emphasizing immersion freezing in the 0 to -30°C regime. The STAC collected particles were characterized by using multimodal micro-spectroscopy techniques such as computer-controlled scanning electron microscopy (CC-SEM) with energy-dispersive X-ray spectroscopy and scanning transmission X-ray microscopy with near-edge X-ray absorption fine structure spectroscopy for their chemical composition, size distribution, and mixing state. The chemical analysis shows a variation of size-resolved chemical composition and mixing state across altitudes at the times of pre-convection and light precipitation. The dominant particle classes include carbonaceous, sulfate with minor dust, and potassium-rich particles. A custom-built IN cell, interfaced with an environmental SEM will also be used to probe the IN potential of the collected particles at a single particle level, emphasizing deposition nucleation in -40 to -60°C temperature regime and to characterize the residuals after IN. Once combined, these results will help to refine climate models and predictions of cloud formation and precipitation patterns in response to environmental changes.