*Zoom* [PhD Thesis Presentation] ‐ Mr. Lin Li– “Storm moisture and landfalling hurricanes"
Presenter: Mr. Lin Li
Supervisor: Prof. Pinaki Chakraborty
Unit: Fluid Mechanics Unit
Zoom URL: https://oist.zoom.us/webinar/register/WN_mz1DOp-5Q5-g_00yWa_9eQ*Registrater in advance for this webinar.*
Title: Storm moisture and landfalling hurricanes
When a hurricane strikes land, it can cause immense destruction to humans and other terrestrial life. Despite its importance, few studies have focused on the dynamics of hurricanes past landfall. By contrast, how hurricanes originate and grow over warm oceans has been extensively studied. Over oceans, moisture from the ocean fuels the intense winds of a hurricane heat engine. Past landfall, the hurricane is severed from this heat source, and its intensity decays. It is generally thought that this decay is a non-thermodynamic process that is dominated by frictional drag with the land surface and where the moisture from the ocean plays no role. Challenging this notion, we argue that the "storm moisture" --- the stock moisture which a hurricane carries as it strikes land --- constitutes a source of heat that modulates the decay of intensity and shapes the internal structure of hurricanes past landfall. The critical, albeit unrecognized, role of storm moisture forms the leitmotif of this thesis, which consists of three parts. First, we analyze intensity data for North Atlantic landfalling hurricanes to show that the timescale of hurricane decay has increased in direct proportion to a contemporaneous rise in the sea-surface temperature over the past 50 years. Second, we show that a landfalling hurricane generates a cold-core in its eye that is distinct from the cold-core in an extratropical cyclone. Third, we show that as the cold-core grows past landfall, its competition with Ekman pumping restructures the flow in the hurricane and can lead to the splitting of the hurricane. In all three cases, we show, using a blend of theory, computational simulations, and field observations, that the storm moisture dictates the hurricane dynamics past landfall.