PhD Defense: Kylie Hoffman
Friday, April 3, 2026 · 9 - 11 AM
Hybrid
·
Physics : 401
ADVISOR: Dr. Belay Demoz
TITLE: Integrated Remote Sensing Observations of Nocturnal Convection Initiation: Moisture Transport and Boundary Layer Convergence Dynamics
ABSTRACT: Nocturnal convection initiation over the Southern Great Plains remains a persistent source of error in warm-season quantitative precipitation forecasts, partly attributable to limited observations of the planetary boundary layer (PBL). This dissertation examines the role of moisture redistribution and mesoscale convergence boundaries in the nocturnal PBL's thermodynamic evolution using a combination of in situ measurements and ground-based remote sensing.
Observations from the PECAN field campaign are used to conduct a resolution analysis and evaluate the ability of passive and active profiling to resolve convection parameters, Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN). Instrument intercomparisons reveal that the ability to clearly resolve mesoscale structures strongly depends on vertical resolution, with resolutions coarser than 200 m resulting in systematic underestimations of CAPE. These results establish that observational capability itself is a limiting factor in nocturnal convection initiation diagnosis, independent of physical understanding. A study of consecutive PECAN observation periods demonstrates that continuous profiling can capture the rapid PBL evolution governing two distinct convective outcomes under similar synoptic and mesoscale setups. These observations reveal that bore-induced mixing redistributed water vapor within the nocturnal PBL, priming the boundary layer’s thermodynamic structure for the following night—a mechanism not captured by radiosonde observations alone. Convection parameters derived from ground-based and airborne remote sensing platforms indicate both spatial and temporal changes in CAPE and CIN tied directly to the differing convective outcomes of the two events.
Finally, investigation of a trailing-end cold front case demonstrates how synoptic-mesoscale convergence boundaries can substantially modify the thermodynamic environment hours prior to frontal passage. Continuous profiling observations demonstrate parcel-specific CAPE exceeding 1200 J kg⁻¹ near 3 km AGL, induced by the front's convergence structure, while surface-based CAPE remains negligible. This case highlights the interaction between synoptic-scale forcing and mesoscale convergence, including elevated divergence and horizontal moisture transport, which together modulate the pre-convective environment. Together, these analyses demonstrate that high-resolution, continuous profiling is essential for resolving the moisture redistribution processes governing nocturnal convection initiation and highlight the value of integrated remote sensing platforms for advancing process-level understanding.
Virtual Attendance
Meeting link: https://umbc.webex.com/meet/kylieh1
Meeting number: 642 456 344
TITLE: Integrated Remote Sensing Observations of Nocturnal Convection Initiation: Moisture Transport and Boundary Layer Convergence Dynamics
ABSTRACT: Nocturnal convection initiation over the Southern Great Plains remains a persistent source of error in warm-season quantitative precipitation forecasts, partly attributable to limited observations of the planetary boundary layer (PBL). This dissertation examines the role of moisture redistribution and mesoscale convergence boundaries in the nocturnal PBL's thermodynamic evolution using a combination of in situ measurements and ground-based remote sensing.
Observations from the PECAN field campaign are used to conduct a resolution analysis and evaluate the ability of passive and active profiling to resolve convection parameters, Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN). Instrument intercomparisons reveal that the ability to clearly resolve mesoscale structures strongly depends on vertical resolution, with resolutions coarser than 200 m resulting in systematic underestimations of CAPE. These results establish that observational capability itself is a limiting factor in nocturnal convection initiation diagnosis, independent of physical understanding. A study of consecutive PECAN observation periods demonstrates that continuous profiling can capture the rapid PBL evolution governing two distinct convective outcomes under similar synoptic and mesoscale setups. These observations reveal that bore-induced mixing redistributed water vapor within the nocturnal PBL, priming the boundary layer’s thermodynamic structure for the following night—a mechanism not captured by radiosonde observations alone. Convection parameters derived from ground-based and airborne remote sensing platforms indicate both spatial and temporal changes in CAPE and CIN tied directly to the differing convective outcomes of the two events.
Finally, investigation of a trailing-end cold front case demonstrates how synoptic-mesoscale convergence boundaries can substantially modify the thermodynamic environment hours prior to frontal passage. Continuous profiling observations demonstrate parcel-specific CAPE exceeding 1200 J kg⁻¹ near 3 km AGL, induced by the front's convergence structure, while surface-based CAPE remains negligible. This case highlights the interaction between synoptic-scale forcing and mesoscale convergence, including elevated divergence and horizontal moisture transport, which together modulate the pre-convective environment. Together, these analyses demonstrate that high-resolution, continuous profiling is essential for resolving the moisture redistribution processes governing nocturnal convection initiation and highlight the value of integrated remote sensing platforms for advancing process-level understanding.
Virtual Attendance
Meeting link: https://umbc.webex.com/meet/kylieh1
Meeting number: 642 456 344