Changes in the Diurnal Timing and Duration of the Great Plains Low-Level Jet

Severe convective hazards, such as tornadoes, hail, and wind, over the Great Plains are among the most impactful weather events in the United States, accounting for billions of dollars in damage annually. These events are consistently associated with a synoptic-scale phenomenon known as the Great Plains Low-Level Jet (GPLLJ), a predominantly nocturnal localized wind maximum in the atmospheric boundary layer (ABL). Other characteristics of the GPLLJ, such as its spatiotemporal extent and magnitude, vary throughout the year. From late spring to early fall, the GPLLJ is a vital contributor to the Great Plains hydroclimate. However, as the climate has changed, characteristics of the GPLLJ, such as its frequency, location, and strength, have followed suit. Given the importance of the GPLLJ for convective activity and precipitation, understanding changes in the spatiotemporal characteristics and intensity of the GPLLJ promotes understanding of convection in a changing climate across this region. While existing literature has predominantly focused on changes in the frequency and spatial extent of the GPLLJ across sub-seasonal to seasonal timescales, limited work addresses the diurnal aspect of the GPLLJ. Using ERA5 reanalysis data, this study accounts for this gap by examining potential changes in the diurnal timing and duration of the GPLLJ over the last 30 years (1993-2022) and its possible relations to observed large-scale spatiotemporal changes in the intensity and frequency of the GPLLJ. Understanding changes in the diurnal characteristics of the GPLLJ, in turn, may aid in forecasting nocturnal convection and associated severe hazards, whose impacts are often augmented at night.