AN EXAMINATION OF HYDROXYL RADICAL: OUR CURRENT UNDERSTANDING OF THE OXIDATIVE CAPACITY OF THE TROPOSPHERE THROUGH EMPIRICAL, BOX, AND GLOBAL MODELING APPROACHES

Hydroxyl radical (OH) is the primary oxidant in the troposphere, initiating the removal of numerous atmospheric species including greenhouse gases, pollutants that are detrimental to human health, and ozone-depleting substances. Because of the complexity of OH chemistry, models vary widely in their OH chemistry schemes and resulting methane (CH4) lifetimes. The current state of knowledge concerning global OH abundances is often contradictory. This body of work encompasses three projects that investigate tropospheric OH from a modeling perspective, with the goal of improving the tropospheric community’s knowledge of the atmospheric lifetime of CH4. First, measurements taken during the airborne CONvective TRansport of Active Species in the Tropics (CONTRAST) field campaign are used to evaluate OH in global models. A box model constrained to measured variables is utilized to infer concentrations of OH along the flight track. Results are used to evaluate global model performance, suggest against the existence of a proposed “OH Hole” in the tropical Western Pacific, and investigate implications of high O3/low H2O filaments on chemical transport to the stratosphere. While methyl chloroform-based estimates of global mean OH suggest that models are overestimating OH, we report evidence that these models are actually underestimating OH in the tropical Western Pacific. The second project examines OH within global models to diagnose differences in CH4 lifetime. I developed an approach to quantify the roles of OH precursor field differences (O3, H2O, CO, NOx, etc.) using a neural network method. This technique enables us to approximate the change in CH4 lifetime resulting from variations in individual precursor fields. The dominant factors driving CH4 lifetime differences between models are O3, CO, and J(O3-O1D). My third project evaluates the effect of climate change on global fields of OH using an empirical model. Observations of H2O and O3 from satellite instruments are combined with a simulation of tropical expansion to derive changes in global mean OH over the past 25 years. We find that increasing H2O and increasing width of the tropics tend to increase global mean OH, countering the increasing CH4 sink and resulting in well-buffered global tropospheric OH concentrations.

(inter)FACE: A Study of Black Families Advocating for their Children’s Education

Black students are consistently overrepresented in categories of academic underachievement. Parent engagement has long been touted as an effective strategy for improving the educational outcomes of Black children. However, most parent engagement research reflects deficit based perspectives frame Black parents as problems that must be fixed or mitigated before they can positively contribute to their children’s education. Consequently, parent engagement research and frameworks ignore the perspectives of Black parents and the assets they use to participate effectively in parent engagement. In this case study, I draw on individual and focus group interview data, documents, and observations, to examine how fifteen Black families, collectively known as FACE: 1) define and participate in parental engagement, 2) experience barriers to and opportunities for engagement, and 3) experience benefits of engagement for their children and their own personal development. Guided by Black Feminist and Critical Race Theories, I show how Black families in this study used a myriad of engagement strategies to improve their children’s educational experiences which were invisible to schools and how they used school-sanctioned engagement activities to meet their own objectives. Ultimately, I argue that school-centered parent engagement frameworks and models are ineffective for empowering Black families and accounting for the essential ways that these families contribute to the well-being of their children. Based on my findings, I discuss implications for theory, practice and policy, and research, and make recommendations for a more family-centered approach to parent engagement.