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Browsing by Author "Barry, Kevin Robert, author"

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    Fire and ice: analyzing ice nucleating particle emissions from western U.S. wildfires
    (Colorado State University. Libraries, 2019) Barry, Kevin Robert, author; Kreidenweis, Sonia, advisor; DeMott, Paul, advisor; Barnes, Elizabeth, committee member; Farmer, Delphine, committee member
    Wildfires in the western U.S. can have impacts on health and air quality and are forecasted to increase in the future. Some of the particles released from wildfires can affect cloud formation through serving as ice nucleating particles (INPs). INPs are necessary for heterogenous ice formation in mixed-phase clouds at temperatures warmer than about -38 °C and can have climate implications from radiative impacts on cloud phase and by affecting cloud lifetime. Wildfires have been shown to be a potential source of INPs from previous ground-based measurement studies, but almost no data exist at the free tropospheric level that is relevant for cloud formation. The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) campaign that was conducted in summer 2018 utilized the NSF/NCAR C-130 to sample many smoke plumes of various ages in the free troposphere and aged smoke in the boundary layer. INP measurements were made with the CSU Continuous Flow Diffusion Chamber (CFDC) and with aerosol filter collections to analyze offline with the CSU Ice Spectrometer (IS). The results presented in this thesis indicate a contribution of smoke to the INP number concentration budget over the plume-background air, but much variability exists in concentrations and in INP composition among fires. Treatments of the filter suspensions show a dominant organic influence in all plume filters analyzed while a biological INP population is evident in several cases. For the South Sugarloaf fire, which had a primary fuel of sagebrush shrubland, the highest INP concentrations of the campaign were measured, and the unique INP temperature spectrum suggests lofting of material from uncombusted plant material. Normalization of INP concentrations measured in WE-CAN confirms that smoke is not an especially efficient source of ice nucleating particles, however emissions impacts may still occur regionally. The determination of a Normalized Excess Mixing Ratio (NEMR) of INP emissions for the first time will permit modeling of such impacts, and possible INP in-plume production will be explored in future research.
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    Ice nucleating particles in the Arctic: measurement and source tracking
    (Colorado State University. Libraries, 2024) Barry, Kevin Robert, author; Kreidenweis, Sonia, advisor; DeMott, Paul, advisor; van den Heever, Susan, committee member; Fischer, Emily, committee member; Trivedi, Pankaj, committee member
    The Arctic landscape is rapidly changing in a warming climate, with sea ice melting and permafrost thawing. Its near-surface air temperature is warming 3.8 times faster than other regions around the world. This rapid warming is known as Arctic amplification. Clouds contribute to this amplification, with their presence and phase is important for determining the surface energy budget. Arctic mixed-phase clouds can last for several days but are not represented well in climate models. Special aerosols, called ice nucleating particles (INPs) trigger ice formation in the atmosphere at temperatures warmer than -38 °C, and thus are important for determining the initiation, lifetime, and radiative properties of these clouds. Observations of INPs, especially over the central Arctic, are limited, and many sources are unknown. This dissertation has the overarching goal of increasing understanding of Arctic INPs. This is achieved through first presenting a full year of INP measurements in the central Arctic, as well as a full year of their composition, using coincident sampling of bacteria and fungi to gain insight into airmass origin. Next, some of the potentially most active Arctic INP sources are explored. Permafrost, which was known previously to contain high levels of INPs, was tested for its activity and persistence in water, and ability to be aerosolized through bubble bursting over several weeks. Then, sources of INPs were surveyed in a region that is controlled by permafrost (a thermokarst landscape). This included field measurements of permafrost, vegetation, sediment, active layer soil, water, and aerosol samples. A high temperature heat test was developed as a diagnostic tool to differentiate sources. Coincidentally, clean working methods to measure INPs were optimized, as efforts to reduce contamination are needed to accurately sample in this region. The main findings from this work suggest a regionally relatively homogenous population of Arctic INPs at most times of year, which is encouraging for efforts to represent them in numerical models across scales and understand their changes in the future. Permafrost-sourced INPs showed high activity and were enhanced near the coast. Unexpectedly, other components of the thermokarst landscape were found to be rich, organic INP reservoirs, emphasizing that the Arctic tundra is a diverse collection of potential contributors to the aerosol.