{"683158":{"#nid":"683158","#data":{"type":"event","title":"PhD Defense by Lifei Yin ","body":[{"value":"\u003Cp\u003ETitle of Thesis: Linking Climate and Air Quality: Insights from Machine Learning, Modeling, and Field Observations\u003Cbr\u003EAbstract of Work:\u0026nbsp;\u003Cbr\u003EClimate change and air pollution are two of the most pressing environmental challenges of the 21st century, both contributing significantly to adverse human health outcomes. Their complex interactions\u2014driven by meteorology, atmospheric chemistry, aerosol-radiation interactions\u2014make understanding their linkages critical for public health and policymaking. This dissertation investigates key pathways of these interactions using machine learning models, chemical transport modeling, and field measurements.\u003Cbr\u003EFirst, we examined the relationship between summertime PM2.5 and O3concentrations and ambient temperature across the contiguous United States, using high-resolution machine learning estimates and ground-based observations. We found widespread positive temperature sensitivities, which have weakened in the eastern U.S. due to emission reductions under the Clean Air Act, but have intensified in the western U.S., driven by increasing wildfire activity.\u0026nbsp;\u003Cbr\u003EIt is important for models to capture this relationship and its long-term pattern for future air quality and climate projection. Therefore, in the second part, we further evaluated and improved the GEOS-Chem chemical transport model, identifying and correcting sources of bias that previously limited its ability to reproduce observed PM2.5\u2013temperature relationships. The improved model showed better agreement with observations and allowed us to quantify the contributions of temperature-sensitive processes. In the eastern U.S., chemical production was the dominant driver of both the magnitude and long-term decline in PM2.5 sensitivity, while transport explained interannual variability. In the west, wildfire emissions emerged as the primary contributor to the recent increase in PM2.5\u2013temperature sensitivity, underscoring the need for stronger fire management policies.\u0026nbsp;\u003Cbr\u003EFinally, we investigated the mixing state of black carbon (BC)\u2014a key light-absorbing aerosol\u2014using in situ measurements from an urban site (Atlanta, GA) and a rural background site (Boone, NC). BC particles in Atlanta exhibited relatively uniform relative coatings due to dominant local sources, while those at the rural site showed greater heterogeneity, reflecting the influence of distinct air masses. The absorption enhancement factor calculated based on realistic mixing states deviated significantly from assumptions of fully internal mixing\u2014by over 40% at the rural site\u2014highlighting the importance of resolving aerosol mixing state in radiative transfer simulations.\u003Cbr\u003EDefense Date: July 28\u003Cbr\u003EDefense Time: 11 am \u2013 2 pm\u003Cbr\u003EDefense Location: L1114\u003Cbr\u003ECommittee: Pengfei Liu (Advisor), Greg Huey, Rodney Weber, Sally Ng, Da Pan\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cstrong\u003EIn-Situ Alloying Strategies for Enhanced Hydrogen Embrittlement Resistance in IN718: A Coupon-Scale Study Utilizing Scanning Laser Epitaxy\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"In-Situ Alloying Strategies for Enhanced Hydrogen Embrittlement Resistance in IN718: A Coupon-Scale Study Utilizing Scanning Laser Epitaxy"}],"uid":"27707","created_gmt":"2025-07-16 16:37:03","changed_gmt":"2025-07-16 16:38:58","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2025-07-21T10:00:00-04:00","event_time_end":"2025-07-21T12:00:00-04:00","event_time_end_last":"2025-07-21T12:00:00-04:00","gmt_time_start":"2025-07-21 14:00:00","gmt_time_end":"2025-07-21 16:00:00","gmt_time_end_last":"2025-07-21 16:00:00","rrule":null,"timezone":"America\/New_York"},"location":"GTMI Room 211 Or On Teams","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}