PhD Defense: Maurice Roots
Location
Physics : 401
Date & Time
March 13, 2025, 3:00 pm – 6:00 pm
Description
ADVISOR: Dr. Belay Demoz
TITLE: Synergy of In-Situ and Remote Sensing Observations for Understanding Ozone Variability and Low-level Jet Dynamics
ABSTRACT: Several decades of regulations on anthropocentric emissions has shown us that air quality is not only driven by chemical reactions but also the mesoscale dynamicss affecting the area. In recent years more emphasis has been placed on the concomitant factors of atmospheric composition that lead to bad air quality. What is currently needed to improve our understanding of air quality episodes is the quantification of dispersion and entertainment of pollutants into the surface layer. This dissertation discusses the complex interplay between atmospheric dynamics and air quality, with a focus on the mechanisms driving tropospheric ozone exceedances in the Mid-Atlantic region of the United States. By integrating a diverse suite of observational platforms - including surface monitoring, balloon-borne sondes, lidars, and Radar Wind Profilers (RWPs)-this research elucidates how mesoscale phenomena, particularly nocturnal low-level jets (NLLJs), contribute to the formation, transport, and accumulation of ozone. A detailed case study of an ozone exceedance event on May 20, 2021, in Maryland demonstrates how the combined effects of long-range pollutant transport and NLLJ-induced downmixing can lead to significant deviations from established seasonal pollution trends. Furthermore, a supervised machine-learning approach was developed to automate the detection and characterization of NLLJs from high-resolution wind profile data, revealing that southwesterly jets in the mid-Atlantic region (MAR-NLLJ) typically exhibit core wind speeds exceeding 10 m/s at core altitudes of 300-500 meters, with peak intensities occurring 3-6 hours after sunset. The work discussed herein, underscore the importance of incorporating mesoscale meteorological processes into air quality models and forecasting systems. The dissertation concludes with recommendations for enhancing observational networks and refining analytical methodologies to improve our understanding of boundary layer dynamics and their implications for pollutant dispersion, thereby supporting more effective air quality management and regulatory decision-making in a changing environmental landscape.
TITLE: Synergy of In-Situ and Remote Sensing Observations for Understanding Ozone Variability and Low-level Jet Dynamics
ABSTRACT: Several decades of regulations on anthropocentric emissions has shown us that air quality is not only driven by chemical reactions but also the mesoscale dynamicss affecting the area. In recent years more emphasis has been placed on the concomitant factors of atmospheric composition that lead to bad air quality. What is currently needed to improve our understanding of air quality episodes is the quantification of dispersion and entertainment of pollutants into the surface layer. This dissertation discusses the complex interplay between atmospheric dynamics and air quality, with a focus on the mechanisms driving tropospheric ozone exceedances in the Mid-Atlantic region of the United States. By integrating a diverse suite of observational platforms - including surface monitoring, balloon-borne sondes, lidars, and Radar Wind Profilers (RWPs)-this research elucidates how mesoscale phenomena, particularly nocturnal low-level jets (NLLJs), contribute to the formation, transport, and accumulation of ozone. A detailed case study of an ozone exceedance event on May 20, 2021, in Maryland demonstrates how the combined effects of long-range pollutant transport and NLLJ-induced downmixing can lead to significant deviations from established seasonal pollution trends. Furthermore, a supervised machine-learning approach was developed to automate the detection and characterization of NLLJs from high-resolution wind profile data, revealing that southwesterly jets in the mid-Atlantic region (MAR-NLLJ) typically exhibit core wind speeds exceeding 10 m/s at core altitudes of 300-500 meters, with peak intensities occurring 3-6 hours after sunset. The work discussed herein, underscore the importance of incorporating mesoscale meteorological processes into air quality models and forecasting systems. The dissertation concludes with recommendations for enhancing observational networks and refining analytical methodologies to improve our understanding of boundary layer dynamics and their implications for pollutant dispersion, thereby supporting more effective air quality management and regulatory decision-making in a changing environmental landscape.
