Future Impact on the Low-Level Jet and its Effects on Wind Energy Generation in Oklahoma

Abstract

Future increases of wind energy density for the United States’ South-Central Plains region have been projected by several previous research examples. The Central Plains’ low-level jet has been projected to become faster and more frequent by the end of the century. This work sought to determine the existence of a significant and explicable climatological relationship between the low-level jet and wind energy resources. Another objective of this work was to update projections of low-level jet characteristics and wind energy metrics before exploring their relationships, since many previous studies have based projections of these quantities on older climate model outputs. Outputs from a collection of recent climate models from over the 21st Century substantiated the projected low-level jet strengthening concluded in previous work, in particular an increase of low-level jet frequency and a poleward shifting of the most common sites of its formation. The necessity of enlisting multiple model outputs in such work was also highlighted, given the tendency of lower-resolution General Circulation Models (GCMs) to project reductions in these low-level jet characteristics, and the known biases that several of these GCMs possess. The current study evaluated wind energy metrics by enlisting a climatological delta method to statistically downscale model-projected wind speed changes onto wind measurements from a collection of Oklahoma Mesonet stations. There was some disagreement with results from previous work, with reductions in wind speed and wind power density projected by the end of the century, and consistent increases (reductions) in the frequency of cut-out (cut-in) events. There was also evidence for diurnal and seasonal variability in the frequency of ramp up/down events, with both quantities possessing higher frequency in spring and summer and during the day. Simple linear regression showed that increases in low-level jet frequency possess a consistent and statistically significant relationship with the wind energy metrics studied in this work, especially for spring and summer and during the night – times of day at which the low-level jet’s occurrence is typically more frequent. The relationship between increased future low-level jet frequency and reductions of ramp event frequency is of interest, given its implications for the grid management of Oklahoma’s future wind energy generation.