03/30/2022
By Erica Gavin

The Kennedy College of Sciences, Department of Environmental, Earth and Atmospheric Sciences, invites you to attend a Master’s thesis defense by Allison Hannigan on “Application of back trajectory analysis to explore the processes that control humidity during extreme heat events in the Northeast United States.”

Candidate Name: Allison Hannigan
Degree Master’s
Defense Date: Wednesday, April 13, 2022
Time: 10 a.m. – 1 p.m.
Location: Room 312, Olney Science Center, North Campus
Thesis/Dissertation Title: Application of back trajectory analysis to explore the processes that control humidity during extreme heat events in the Northeast United States

Advisor: Christopher Skinner, Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell

Committee:

  • Christopher Skinner, Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell
  • Mathew Barlow, Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell
  • Frank Colby, Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell

Brief Abstract:

Over the last several decades, extreme heat events have increased in frequency, intensity, and duration in the United States. Studies have attributed these trends to a warming climate, and therefore, it is expected that prolonged periods of abnormally hot temperatures will become more frequent through the 21st century. High temperatures alone can have harmful impacts on the human body, but when coupled with high humidity, these events become especially threatening to people. Despite its dense population, extreme heat in the Northeast U.S. has received relatively little attention, and a comprehensive understanding of what drives high humidity during these extreme heat events is lacking. Here, we utilize the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model to study atmospheric moisture exchanges and concentrations along the trajectories of air parcels that precede heat wave events at major population centers across the Northeast U.S. Results indicate that air parcels from humid and dry heat wave events are often sourced from different geographic regions (e.g., ocean vs land) and traverse regions with very different surface turbulent fluxes on the way to the Northeast. In instances in which the geographic pathway on dry and humid heat events is similar, distinctions in starting altitude, vertical motion, and surface fluxes due to soil moisture content are observed, and it is these processes that play an important role in shaping the relative humidity of the heat wave. Identification of the processes that distinguish dry and humid heat waves allows for improved forecasting of and preparation for such events, and a greater understanding of the potential impacts that an event will have on populations in the Northeast U.S.