Future Trends in Upper-Atmospheric Shear Instability from Climate Change

Abstract

Understanding how jet streams respond to a warming climate is crucial for anticipating changes in atmospheric circulation and their broader impacts. Previous studies have highlighted the influence of anthropogenic warming on the meridional temperature gradient, which directly affects jet stream dynamics and variability. This study investigates projected trends in upper-level jet stream shear instability under future climate change scenarios using CMIP6 multimodel simulations. Building on previous findings linking anthropogenic warming to strengthened meridional temperature gradients, we analyze annual means of zonal wind speed, vertical wind shear, and stratification profiles from 2015 to 2100 globally. Results show strengthened multimodel annual-mean vertical shear at 250 hPa, particularly in high-emission scenarios, with trends ranging from 0.04 to 0.11 m s21 (100 hPa)21 decade21 depending on the scenario and region, equivalent to a total relative increase of 16%–27% over 86 years. Decreasing trends are observed in the annual-mean Brunt–Väisälä frequency N2 at 250 hPa, with multimodel ensemble mean values across regions ranging from 20.018 to 20.040 3 1024 s22 decade21 for lower and higher emission scenarios, respectively, equating to a total relative decrease of 10%–20%. Similarly, the annual-mean Richardson number Ri shows decreasing trends from 20.014 to 20.050 decade21 across emission scenarios and regions, which is a total relative decrease of 38%–47%. These findings suggest more favorable conditions for the generation of clear-air turbulence (CAT), posing critical challenges for aviation safety and operations in a warming climate.