Abstract
The southerly Great Plains low-level jet (GPLLJ) is one of the most significant circulation features of the central U.S. linking large-scale atmospheric circulation with the regional climate. GPLLJs transport heat and moisture, contribute to thunderstorm and severe weather formation, provide a corridor for the springtime migration of birds and insects, enhance wind energy availability, and disperse air pollution. We assess future changes in GPLLJ frequency using an eight member ensemble of dynamically-downscaled climate simulations for the mid-21st century. Nocturnal GPLLJ frequency is projected to increase in the southern plains in spring and in the central plains in summer, whereas current climatological patterns persist into the future for daytime and cool season GPLLJs. The relationship between future GPLLJ frequency and the extent and strength of anticyclonic airflow over eastern North America varies with season. Most simulations project a westward shift of anticyclonic airflow in summer, but uncertainty is larger for spring with only half of the simulations suggesting a westward expansion. The choice of regional climate model and the driving lateral boundary conditions have a large influence on the projected future changes in GPLLJ frequency and highlight the importance of multi-model ensembles to estimate the uncertainty surrounding the future GPLLJ climatology.
Highlights
The Great Plains low-level jet (GPLLJ), a fast-moving southerly airstream in the lower troposphere, is one of the most important atmospheric circulation features influencing the central U.S Roughly one-third of the moisture entering this region is transported from the Gulf of Mexico by the GPLLJ1, and convergence downstream of the jet promotes the formation of thunderstorms and convective precipitation[2]
The GPLLJ contributes to the wind energy resources of the Great Plains with wind power potential estimated at 25% higher when a GPLLJ is present[13], the wind shear below the jet poses a hazard to the lifetime and performance of wind turbines[14]
We use an ensemble of dynamically-downscaled climate simulations available from the North American Regional Climate Change Assessment Program (NARCCAP)[36] to assess future changes in the GPLLJ climatology and the associated uncertainty
Summary
We use an ensemble of dynamically-downscaled climate simulations available from the North American Regional Climate Change Assessment Program (NARCCAP)[36] to assess future changes in the GPLLJ climatology and the associated uncertainty Those NARCCAP simulations with wind information at multiple vertical levels are included in the analysis, for a total of eight RCM_AOGCM combinations obtained from four RCMs (CRCM, WRFG, RCM3, and HRM3) with four AOGCMs (CCSM, CGCM3, GFDL, and HADCM3) used to drive the RCMs at the lateral boundaries of their regional domains (see Table S1 for a listing of simulations and explanation of abbreviated model names). We further compare monthly GPLLJ frequencies at 3-hourly time steps obtained from the RCM_AOGCM simulations for the baseline period to long-term (1979–2009) climatological values calculated[21] from the North American Regional Reanalysis (NARR)[41] at 0600 UTC for April through September (Figure S1). The seasonality of jet frequencies in the NARCCAP simulations is stronger than that for NARR, especially for the WRFG_CCSM, WRFG_CGCM3, and RCM3_CGCM3 simulations
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