Degree
Doctor of Philosophy (PhD)
Department
Department of Oceanography & Coastal Sciences
Document Type
Dissertation
Abstract
Atmospheric aerosols have been found to influence tropical cyclone (TC) and flood event development. In this study, the Weather Research and Forecasting model is applied to investigate specific microphysical impacts and aerosol sensitivity to heavy precipitation and TC events in the U.S. Gulf Coastal area. The Thompson aerosol-aware scheme with regular and adjusted aerosol concentration scenarios is used to quantify precipitation, wind field, horizontal/vertical structures, and track variations, by aerosol mixing ratio. In general, results for the three storms analyzed (the 2016 Baton Rouge, Louisiana, flood event (Chapter 2); Hurricane Harvey in 2017 (Chapter 3); and an idealized storm event (Chapter 4)) suggest that aerosols influence TCs through interconnected microphysical and dynamical processes. Excessive aerosol loadings delay heavy precipitation occurrence but amplify peak rainfall in a more spatially-confined area; cleaner-air scenarios trigger earlier rain with a reduced extreme precipitation area under “normal” aerosol conditions.
Chapter 2 mirrors the overall results, with elevated aerosol concentrations promoting more extreme but localized precipitation and diminished overall precipitation volume. Chapter 3 shows northwestward storm track displacement during dissipation and reduced geopotential heights for all atmospheric pressure levels following Harvey’s second landfall, in both the cleaner-air and more-polluted-air scenarios, with the latter promoting a stronger warm-core structure at first landfall, compared to the actual track. Chapter 4 emphasizes aerosols' capacity to reshape TC behavior via postponed precipitation initiation, amplified convective organization, and track modulation primarily through microphysical processes, initiating cascading atmospheric interactions including complex microphysical and dynamical feedback loops. These changes propagate through interactions among hydrometeors and precipitation, altering lower-level winds, temperature, and updrafts, which shift wind direction and reduce sea level pressure. Subsequent complexities arise as temperature and wind mutually influence each other through energy exchange, hydrometeor conversion, and vertical motion. Ultimately, excessive aerosols may delay precipitation but foster stronger, deeper convective systems with more compact-tracking TCs due to prolonged energy retention and intensified circulation. These interlinkages underscore aerosols’ critical role in linking environmental pollution to storm hazards through coupled microphysical-dynamical feedback loops. Collectively, these results may assist in calibrating weather forecast models to enhance protection of life and property in extreme precipitation situations.
Date
5-28-2025
Recommended Citation
cao, wenjia, "Investigating the Role of Aerosols in Extreme Precipitation Events along the Gulf Coast of the U.S.A." (2025). LSU Doctoral Dissertations. 6809.
https://repository.lsu.edu/gradschool_dissertations/6809
Committee Chair
Rohli, Robert V.