Viewed from the International Space Station, Hurricane Isabel made landfall on鈥疭ept. 18, 2003, in eastern North Carolina, near Drum Inlet, along the Outer Banks.鈥疶he storm was a Category 2 hurricane at the time of landfall.鈥�
Courtesy NASA
Dr. Xiaomin Chen, a researcher at 草榴社区, in , a journal of the American Geophysical Union (AGU), that offers a new model capable of resolving turbulence and eddies within hurricanes as they transition from water to land. The innovation provides a way to quantify the uncertainty of 10-meter wind estimates above the surface derived from different鈥痮bservation-based approaches for the first time. These estimates are crucial for classifying hurricanes based on the , a 1 to 5 rating system that is based on one-minute sustained wind speed and used to estimate potential property damage and the danger to life.
Chart depicting 10-meter wind speed from a turbulence-resolving model simulation, overlaid by two virtual sondes trajectories released at鈥痶he maximum and minimum鈥痺ind location from鈥�1- and 6-km inland, respectively.
Courtesy Xiaomin Chen
鈥淥btaining wind measurements overland under hurricane鈥痗onditions is risky and challenging,鈥� says Chen, an assistant professor of atmospherics and Earth science at UAH, a part of The University of Alabama System. 鈥淓ither the observational instruments鈥痮r power infrastructure may fail in those extreme conditions. This study leverages a novel turbulence-resolving modeling framework to 鈥榞enerate鈥� these hard-to-obtain measurements in the coastal region.鈥�
Chen鈥檚 primary research is aimed at understanding the boundary layer processes that contribute to the intensity and structural changes of hurricanes at various stages, including during and post landfall. His work utilizes a combination of manned and unmanned aircraft observations and turbulence-resolving large-eddy simulations to improve the modeling of boundary-layer processes in hurricane conditions.
鈥淗urricanes feed on boundary layer heat fluxes and dissipate through boundary layer friction,鈥� the researcher notes. 鈥淲ind-related compound hazards occur鈥痠n the boundary layers. One interesting phenomenon during hurricane landfalls is the formation of an internal boundary layer (IBL) overland.鈥�
IBLs are鈥痳egions where atmospheric flow adapts to changes in surface conditions, like the coastal interface between land and ocean.鈥疶hese changes cause wind patterns to shift, leading to the formation of an IBL where the wind profile adjusts to the new surface conditions.鈥疷nderstanding IBLs is vital to accurately model and predict hurricane intensity and near-surface wind hazards, especially during landfall.鈥�
Dr. Xiaomin Chen, an assistant professor of atmospherics and Earth science at UAH.
Michael Mercier | UAH
鈥淒ue to the relatively sparse near-surface anemometer wind measurements, earlier studies used ground-based radar-retrieved or radiosonde winds aloft to project the 10-m wind speeds over a relatively broad鈥痑rea,鈥� Chen says. 鈥淭hese methods鈥痙o not properly account for the IBLs, and鈥痶he related uncertainty in the 10-m wind estimates is challenging to assess.鈥疐ine-resolution, turbulence-resolving modeling resolves the IBL properly, offering the first opportunity to quantify the uncertainty related to the 10-m wind estimates for those methods.鈥�
Chen uses specially configured turbulence-resolving computer model simulations to provide insights into the effects of land surface types and distance inland on the near-surface wind profile to glean findings that can guide future field campaigns and hurricane landfall studies.
鈥淭he novelty of these turbulence-resolving simulations is the inclusion of actual hurricane physics across a small-patch model domain, offering a computationally efficient approach to test the impact of different factors, such as land surface types. In contrast, turbulence-resolving simulations of the entire tropical cyclone circulation extending hundreds of miles remains computationally prohibitive for most modellers,鈥� the researcher notes.
鈥淭he following work will involve two parallel efforts,鈥� Chen says regarding the future of this research. 鈥淥ne, we aim to run these turbulence-resolving models over more realistic terrain along the Gulf coast and study the wind gusts. And two, we will leverage the ground-based radars and near-surface wind measurements to explore a better approach to estimate 10-m winds during hurricane landfalls. These missions are supported by our recently funded National Science Foundation project, (WHIRLTC).鈥�