Browsing by Author "Brooks, Sarah"

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Collaborative Research: Quantifying the Role of Pollen in Cloud Formation through Measurements and Modeling
Atmospheric Sciences; TAMU; https://hdl.handle.net/20.500.14641/214; National Science Foundation
While pollen is emitted from the Earth's surface in large quantities from vegetation, these emissions are typically excluded from inventories due to the large size of pollen grains. However, recent studies have shown that pollen grains easily rupture when wet, forming smaller sub pollen particles (SPP); these SPP have not been well-studied. The central goal of this study is to accurately establish the amount of SPP produced by pollen rupture and to determine its cloud formation properties. This study will include a series of experiments utilizing a plant chamber and atmospheric modeling simulations. The laboratory measurements will (1) Quantify the number of SPP emitted from a single pollen grain and from a plant under atmospheric conditions, (2) Determine the supersaturation required for cloud condensation nuclei (CCN) activation, and (3) Determine the temperatures and relative humidities required for ice nucleating particles (INP) activation. These results will provide critical input for an online pollen emissions model that will be used with the Weather Research and Forecasting model coupled with Chemistry model (WRF-Chem) to (1) Implement the pollen emission rupture mechanism in WRF-Chem, (2) Utilize measured rupture data to improve simulations of pollen rupture, and (3) Conduct new simulations that account for the indirect effects from both warm and cold clouds using CCN and INP activation measurements. This interdisciplinary project uses laboratory and modeling components to maximize the value of the measurements for improving model estimates of pollen effects on cloud formation. The work will also be integrated in an undergraduate course that will introduce pollen sampling equipment and instruct students on the basics of aerosol and climate modeling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES)
Atmospheric Sciences; TAMU; https://hdl.handle.net/20.500.14641/214; NASA-Langley Research Center
Atmospheric aerosols modulate climate through direct interactions with sunlight and through their indirect role in influencing cloud formation and properties (Andreae and Rosenfeld, 2008; Carslaw et al., 2013). Quantification of marine aerosol-cloud interactions is a major source of uncertainty in estimates of aerosol radiative forcing (Boers and Krummel, 1998; Quinn and Bates, 2011). The sea surface has long been considered a source of aerosols, some of which act as cloud condensation nuclei (CCN) (Charlson et al., 1987). However, it is debatable to what extent marine aerosol influence clouds (Ayers and Cainey, 2007; Quinn and Bates, 2011), especially given that pollution, ship tracks may also contribute to the cloud-active aerosol population (Christensen and Stephens, 2012; Coggon et al., 2012; Hudson and Noble, 2014). Further, even in an unpolluted environment, the relative contributions of primary aerosols arriving in the atmosphere due to wave breaking activities and secondary aerosols (formed from gas phase precursors) are not known. To quantify marine aerosols and their impacts on cloud formation requires additional measurements of aerosol and CCN concentrations are needed, especially in pristine marine environments.
Viscous Organic Liquids and Catalysis of Atmospheric Ice Nucleation
Atmospheric Sciences; TAMU; https://hdl.handle.net/20.500.14641/214; National Science Foundation
This award from the Environmental Chemical Sciences Program in the NSF Division of Chemistry supports Prof. Sarah Brooks at Texas A&M University. Prof. Brooks and her students study the role of secondary organic aerosols SAO) in the nucleation of atmospheric ice particles. Recent measurements indicate that several current assumptions about the organic aerosol phase and the cloud-forming properties may be incorrect. First, the majority of SOA in the troposphere exist in a viscous, rather free-flowing liquid state. Second, the presence of viscous organic aerosols represents a previously unrecognized supply of particles capable of causing the freezing of ice crystals in clouds. The data collected are used to assess the role of viscous phases and retarded water diffusion in atmospheric ice nucleation processes. The project also includes the training of graduate students, undergraduate students, and high school students. During summers at Texas A&M, high school students attend the campus-wide TAMU Youth Adventure Program to participate in lecture and laboratory activities including, "The role of viscosity in the foods we love." The team collects quantitative data on the phase, water diffusion, and ice nucleating ability of representative organic compounds and mixtures. The phases of sample aerosols are characterized by their temperature-dependent viscosities and the temperature at which they transition from liquid to glass using specialized spectroscopic techniques. In addition, the freezing temperatures of all samples are determined using our custom ice microscope technique. Taken together the data are used to evaluate whether a minimum glass transition temperature requirement exists for viscous aerosol to facilitate the freezing of droplets. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
Viscous Organic Liquids and Catalysis of Atmospheric Ice Nucleation
Atmospheric Sciences; TAMU; https://hdl.handle.net/20.500.14641/214; National Science Foundation
This award from the Environmental Chemical Sciences Program in the NSF Division of Chemistry supports Prof. Sarah Brooks at Texas A&M University. Prof. Brooks and her students study the role of secondary organic aerosols SAO) in the nucleation of atmospheric ice particles. Recent measurements indicate that several current assumptions about the organic aerosol phase and the cloud-forming properties may be incorrect. First, the majority of SOA in the troposphere exist in a viscous, rather free-flowing liquid state. Second, the presence of viscous organic aerosols represents a previously unrecognized supply of particles capable of causing the freezing of ice crystals in clouds. The data collected are used to assess the role of viscous phases and retarded water diffusion in atmospheric ice nucleation processes. The project also includes the training of graduate students, undergraduate students, and high school students. During summers at Texas A&M, high school students attend the campus-wide TAMU Youth Adventure Program to participate in lecture and laboratory activities including, "The role of viscosity in the foods we love." The team collects quantitative data on the phase, water diffusion, and ice nucleating ability of representative organic compounds and mixtures. The phases of sample aerosols are characterized by their temperature-dependent viscosities and the temperature at which they transition from liquid to glass using specialized spectroscopic techniques. In addition, the freezing temperatures of all samples are determined using our custom ice microscope technique. Taken together the data are used to evaluate whether a minimum glass transition temperature requirement exists for viscous aerosol to facilitate the freezing of droplets. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.