Projected Increase in Clear-Air Turbulence over Southwest China Under Climate Change

Changes in aviation turbulence at cruise altitudes have important implications for aviation safety under global warming scenarios in the future. Using projections from the NorESM2-MM model within the CMIP6 framework, this study evaluates changes in clear-air turbulence (CAT) at 250 hPa over Southwest China during the twenty-first century based on an ensemble of 15 diagnostic indices. The results show: (1) Historical moderate-or-greater (MOG) CAT peaks in a zonal belt near 30–35° N, with annual frequencies up to 1.6% over the Hengduan and Karakoram Mountains. Future increases remain focused in this belt, are stronger and more extensive under SSP5-8.5, peak in winter and spring, and weaken over much of the Plateau interior in summer. (2) Future changes are intensity-dependent: stronger categories show larger relative increases, and PDF changes are concentrated in the right tail, indicating amplified extreme turbulence. The 19-year moving-average time series shows that MOG-CAT increases by 28.3% and 36.5% under SSP2-4.5 and SSP5-8.5, respectively, by the mid-twenty-first century, and by 26.0% and 69.4% by the late twenty-first century. (3) Along the Chengdu–Lhasa corridor, winter MOG-CAT increases in all three segments. Under SSP5-8.5, median increases are about 50% in the Basin and Plateau segments and about 85% in the Transition segment, with most diagnostics ranging from 50% to 180%. (4) High-emission scenarios are more likely to cause turbulence and instability in the southwestern region, potentially posing greater challenges for aviation turbulence warning and safety assurance.