Spatiotemporal Trends and Environmental Controls of Turbulence Near Thunderstorms Over The United States

Abstract

Atmospheric turbulence near thunderstorms represents one of the most persistent haz- ards in commercial aviation, yet the spatial extent, environmental controls, and storm- structural dependencies of this hazard remain incompletely understood. Current fed- eral guidelines recommend maintaining at least 20 miles of lateral separation from convective storm boundaries, a threshold that growing evidence suggests substantially underestimates the true area of elevated risk. This thesis uses over 37 million au- tomated in-situ eddy dissipation rate (EDR) observations from commercial aircraft, paired with high-resolution GridRad radar data, to construct a modern spatiotempo- ral climatology of turbulence near thunderstorms over the contiguous United States and to examine how storm characteristics modulate near-storm turbulence risk. The southeastern United States emerges as the nation’s primary turbulence-near- thunderstorms hotspot, with the Gulf Coast, northern Florida, and portions of Missis- sippi and Alabama exhibiting the highest convective percentages and shortest return intervals between moderate-or-greater (MoG) turbulence events. However, convective frequency alone proves insufficient to explain the observed turbulence distribution, as large-scale environmental factors including upper-level wind speed, temperature, and static stability each modulate the spatial reach and intensity of convectively induced turbulence. Winter emerges as the season of highest relative risk in storm-present environments despite exhibiting the lowest overall convective frequency, attributable to the stronger and more southerly positioned wintertime jet stream. A pronounced diurnal cycle is identified, with relative risk peaking during the overnight hours despite a concurrent decline in convective activity.