Coordinated Uncrewed Aerial System Sampling of Boundary Layer Structures

The atmosphere adjacent to the ground is called the atmospheric boundary layer. It plays an important role in interactions between Earth’s surface and the atmosphere. Air flow in the boundary layer can be turbulent, which is difficult to model. Nevertheless, the success of weather models depends critically on accurate representations of the boundary layer. Current models do not account for large, organized, rolling air currents that strongly affect flow inside the boundary layer. Most studies of these organized rolling motions, which are called coherent structures, are based on laboratory experiments or computer simulations. This project will use formations of fixed-wing drones to collect real-world data on air movement inside the boundary layer. The studies will be designed to identify key factors that govern the formation of organized rolling motions and their subsequent behavior. The project will provide opportunities for undergraduate students to participate in research. They will be key members of the team, serving as system operators, safety officers, and aircraft managers, while being trained on the scientific objectives of the research. The measurements will focus on evaluating several hypotheses about the formation and influence of a structure called horizontal convective rolls. The project will investigate (1) the critical stability threshold at which horizontal convective rolls develop; (2) whether their formation mechanism represents an evolution of superstructures observed under neutral stability conditions; (3) the contribution of roll structures to mass, momentum, and energy transport under conditions in which they form; and (4) their influence on the anisotropy of smaller-scale turbulence. Measurements will be conducted using a leader-follower approach, in which a lead aircraft is tasked with navigation and the rest are tasked with maintaining their relative spatial separation. This separation will be designed so that wind velocity measurements made by each aircraft can be used to determine the velocity gradient tensor, yielding unprecedented information about the vorticity and turbulence within the coherent structures. This information will support the broader objectives of the project by enabling advances in boundary layer parameterizations, ultimately enhancing the accuracy of meteorological models. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2531196 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Sean Bailey | Institution: University of Kentucky Research Foundation, LEXINGTON, KY | Award Amount: $612,447 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2531196 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2531196.html