Doctor of Philosophy
Alexander Soloviev, Ph.D.
Brian Haus, Ph.D.
Isaac Ginis, Ph.D.
Richard Dodge, Ph.D.
sea spray, tropical cyclone, hurricane, air-sea interaction, spume, computational fluid dynamics, air-sea fluxes, rapid intensification, CFD, ANSYS Fluent, surfactants, surface-active materials, air-sea gas exchange, SSGF, sea spray generation function, numerical modeling, ocean circulation, western boundary currents, Gulf Stream, laboratory experiments, field observations
Tropical cyclone intensity prediction remains a challenge despite computational and observational developments because successful intensity forecasting requires implementing a multitude of atmospheric and oceanic processes. Hurricane Maria 2017 and Hurricane Dorian 2019 serve as prime examples of rapidly intensifying storms that devastated communities in the Caribbean. A lack of understanding and parameterization of crucial physics involved in tropical cyclone intensity in existing forecast models may have led to these and other forecasting errors.
Microscale physical processes at the air-sea interface are a major factor in intensification of tropical cyclones that are often unaccounted for in forecasting models since they are difficult to study in the field and laboratory and are therefore not well understood. An ongoing uncertainty in tropical cyclone dynamics is the sea spray generation function (SSGF). While multiple estimates of the SSGF have been produced, a lack of experimental data in high wind conditions makes it difficult to establish a confident SSGF for tropical cyclones. Surface active agents impact spray generation, causing variation in spray diameter and an increase in generation that may influence heat, momentum, and gas exchanges during tropical cyclones. To better understand these processes, a computational fluid dynamics model was developed that simulates spray generation under all five tropical cyclone category conditions and resolves spray with radii starting from 100-mm. The numerical results were validated with Category 1 data from a laboratory experiment at the University of Miami. SSGFs calculated from the model revealed an increase in the spray generation under all categories of tropical cyclone conditions except Category 4 and Category 5 conditions, where little to no impact of surfactants on spray generation was found. This phenomenon might be explained by a change in regime under major tropical cyclones.
Additionally, small to mesoscale ocean circulation and characteristics, particularly in environments such as a western boundary current, lead to complex interaction between ocean circulation and tropical cyclones. Not only are ocean dynamics in the open ocean affected by tropical cyclones, but the impacts can extend to coasts outside of the predicted storm impact area, leading to unprepared coastal communities due to these poorly understood interactions. This can improve parameterizations of variables such as mixing and fluxes in tropical cyclone forecasting models. An additional computational fluid dynamics model has been developed that predicts and characterizes small to mesoscale ocean circulation and dynamics in a western boundary current.
This body of work aims to further understand ocean circulation in the surface layer in western boundary currents and complex microphysics at the air-sea interface during tropical cyclones including spray and spume generation, evaporation, and related fluxes, air-sea gas exchange, and the effects of factors such as surfactants. The multitude of ocean dynamics and air-sea interaction processes to be studied in this work converge to strive for a more complete understanding of the ocean water column and the air-sea interface under tropical cyclones that could ideally be implemented into tropical cyclone prediction models to improve intensity forecasting.
Breanna Lynn Cain Vanderplow. 2023. Microscale to Mesoscale Modeling of the Ocean Under Tropical Cyclones: Effects of Sea Spray and Surfactants on Tropical Cyclone Intensity and Air-Sea Gas Exchange. Doctoral dissertation. Nova Southeastern University. Retrieved from NSUWorks, . (162)